Guidance document on the application of water balances for supporting the implementation of the WFD : final : version 6.1 – 18/05/2015.
Date: 2016-04-04
Institutions: Directorate-General for Environment
Subjects: EU environmental policy, directive (EU), environmental monitoring, research report, user guide, water management, watercourse

Technical Report - 2015 - 090

Guidance document on the application 
of water balances for supporting 
the implementation of the WFD

Final – Version 6.1 – 18/05/2015

Environment

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Guidance document on the application 
of water balances for supporting 
the implementation of the WFD

Final – Version 6.1 – 18/05/2015

Table of content 

1. 

INTRODUCTION ....................................................................................................... 4 

1.1.  Context .............................................................................................................. 4 
1.2.  A guidance: what for? ....................................................................................... 7 
1.3.  Guide to the reader ............................................................................................ 9 

2.  KEY COMPONENTS OF WATER BALANCES ................................................... 11 

2.1.  The key components of the hydrological cycle ............................................... 11 
2.2.  From water balance to  a detailed list  of water quantity  related parameters 

used to support policy making ........................................................................ 15 

3.  KEY ISSUES IN DEVELOPING WATER BALANCES ....................................... 24 

3.1.  Developing water balances…. at the right scale ............................................. 24 
3.2.  Data sources (quality) and uncertainties ......................................................... 25 
3.3.  Correctly identifying water availability and accounting for ecological needs 

(links to e-flows) ............................................................................................. 27 

4.  APPLYING WATER BALANCES IN PRACTICE ................................................ 31 

5.  USING WATER BALANCES FOR SUPPORTING WATER MANAGEMENT .. 39 

5.1.  Supporting the characterization of river basins and the identification of key 

water management issues ................................................................................ 39 
5.2.  Supporting the selection of measures for the WFD PoM ................................ 39 
5.3.  Target setting and allocation ........................................................................... 41 
5.4.  Adapting to climate change ............................................................................. 42 
5.5. 
Identifying room for improvement in resource efficiency .............................. 42 
5.6.  Contributing to informing and reporting on water policy implementation ..... 43 

6.  EXPANDING  THE  PHYSICAL  WATER  BALANCE  FOR  ADDRESSING 

COMPLEMENTARY WATER MANAGEMENT ISSUES ................................... 45 

6.1.  Expanding water balance to account for water quality ................................... 45 
6.2. 
Integrating the economic dimensions of water use and management ............. 45 
6.3.  EEA and Eurostat related works ..................................................................... 51 

7.  RECOMMENDATIONS AND CONCLUSIONS ................................................... 53 

8.  LIST OF REFERENCES .......................................................................................... 55 

ANNEXES ........................................................................................................................ 59 

ANNEX I – ILLUSTRATING THE APPLICATION OF WATER BALANCES .......... 59 

Case study #1: Ali-Efenti River Basin, Greece (ABOT project, DG ENV) ............. 59 
Case study #2: Tiber River Basin, Italy (ABOT project, DG ENV) ......................... 62 
Case study #3: Vit River Basin, Bulgaria (ABOT project, DG ENV) ...................... 65 
Case study #4: Mulde River Basin, Germany (ABOT project, DG ENV) ............... 68 
Case study #5: Arno River Basin, Germany (PAWA project, DG ENV) ................. 71 
Case study #6: Slovenia ............................................................................................ 77 

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Case study #7: The Jeziorka River Catchment, Poland ............................................ 82 
Case study #8: Use of water resource balance as a tool for the assessment of the 
quantitative  relation  between  water  requirements  (including  the  minimum 
balance discharge) and water resources – example from Slovakia ................. 85 
1.1  Objective of the Case study ............................................................................. 85 
1.2  Policy and management context ...................................................................... 85 

2  DETAILED INFORMATION .................................................................................. 85 

2.1  Practical Tasks (in case of methods and/or procedures) ................................. 85 
2.2  Temporal and spatial scales ............................................................................. 86 
2.3  Type of analysis or tool ................................................................................... 86 
2.4 
Information and data requirements.................................................................. 91 
2.5  Testing of results ............................................................................................. 93 
2.6  Current application of the method/initiative ................................................... 93 
2.7  Learned lessons  - Conclusions – Recommendations for application within 

the concept of Eflows ...................................................................................... 94 
Contact information................................................................................................... 94 

ANNEX  II  –  KEY  METHODOLOGICAL  LESSONS  FROM  THE  EU-FUNDED 

PILOT STUDIES ...................................................................................................... 96 

ANNEX  III    –COMPARISON  BETWEEN  THE  “SEEAW  ASSET  ACCOUNTS” 

AND THE “WATER BALANCE” COMPONENTS ............................................. 120 

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1.  INTRODUCTION 

1.1.  Context 

The vital importance of water for supporting the functioning of ecosystems while contributing 
at the same time to economic development is widely recognized in all parts of Europe today. 
Historically, most attention has been given to water quality issues as illustrated by the early 
European Union (EU) water directives developed during the 1970s and the early 1980s that 
aimed  at  ensuring  the  good  quality  of  waters  used  for  different  purposes  (e.g.  for  drinking, 
water swimming, fishing, etc.).  

With  the  increasing  imbalance  between  water  supply  and  water  demand  1in  many  parts  of 
Europe,  including  also  some  in  parts  of  Northern  Europe  [1],  potentially  exacerbated  by 
changes  in  climate  during  the  past  few  decades,  water  availability  and  water  scarcity  has 
progressively  emerged  as  a  key  issue  in  national  and  EU  water  policy  making  and 
implementation,  as 
the  policy  objectives  of  different  Directives  and 
Communications (Table 1). 

illustrated 

in 

Table  1.  Policy  objectives  related  to  water  availability  in  different  directives,  working 
documents, communications and strategies. 

EU Directive/Communication/ Strategy 
EU Water Framework Directive (WFD) 
2000/60/EC, daughter directives (2000) 
[2], and guidance documents within the 
Common Implementation Strategy.  
EC Communication “Addressing the 
challenge of water scarcity and drought 
in the European Union”  
 (2007) [3] 

EC Communication “Blueprint to 
Safeguard Europe’s Water” (2012) [4] 

EU Strategy on Adaptation to Climate 
Change [5]. 
EC Communication “White Paper: 

Policy Objective 

Ensure a good quantitative status of groundwater bodies;  
Achieve good ecological status of surface water bodies (including in terms of 
supporting environmental river flow requirements);  
Identify significant pressures from abstraction (Art. 5). 

Encourage Member States (MS) to identify river basins which face quasi-
permanent or permanent water stress or scarcity;  
Improve drought risk management;  
Improve knowledge and data collection. 

Put quantitative water management on a much more solid foundation 
(including identification of the ecological flow –i.e. the amount of water 
required for the aquatic ecosystem to continue to thrive and provide services) 
and address the issue of over-allocation at the river basin scale;  
Recognize that water quality and quantity are intimately related within the 
concept of good status; 
Develop water efficiency targets for river basins which are (or are projected to 
be) water stressed, on the basis of water stress indicators developed in the 
Common Implementation Strategy (CIS) process and applied at river basin 
level; 
Implement Water Accounts at river basin and sub-catchment level: they can 
tell water managers how much water flows in and out of a river basin and how 
much water can realistically be expected to be available before allocation 
takes place; 
Identify and reduce of illegal abstraction/impoundments. 
Build a solid knowledge base on the impact and consequences of climate 
change for EU water resources as a basis for developing sound adaptation 
strategies for water. (Water resources are directly impacted by climate change, 
and the management of these resources affects the vulnerability of 

1 ‘Water demand’ is used in the document according to the meaning reflected in sectoral EU policy and water 
resources management (i.e. water requirements of specific quality for different purposes), which may differ from 
its economic definitions. See Box 5. 

4 

 
 
                                                 
 
EU Directive/Communication/ Strategy 
Adapting to climate change: Towards a 
European framework for action” (2009) 
[6]. 

Policy Objective 
ecosystems, socio-economic activities and human health. Water management 
is also expected to play an increasingly central role in adaptation.   
Climate change is projected to lead to major changes in water availability 
across Europe with increasing water scarcity and droughts mainly in Southern 
Europe and increasing risk of floods throughout most of Europe). 

UN-Water: Water in the post-2015 
development agenda (2014) [7]. 

Sustainable Development Goals (SDGs) 
for water: core indicators related to 
Target B-water resources management 
(WRM). 

GEOSS Water Strategy 

Integrated Global Water Cycle 
Observation (IGWCO) 

Target B: Improve by (x %) the sustainable use and development of water 
resources in all countries. 
Suggested action:  
-  Bringing freshwater withdrawals into line with sustainably available water 
resources. 

Develop widely available, sustained water cycle data sets and related 
information products, at both global and basin scales, tailored to the near- and 
long-term needs of stakeholders and end-users; 
Guide decisions on water cycle observations;  
Promote strategies for the acquisition, processing and distribution of data 
products needed for effective management of the world's water resources. 

The  system  of  Integrated  Environmental  and  Economic  Accounting  (SEEA)  of  the  United 
Nations Statistics Division was created in 1993 and modified on 2002. The main aim has been 
to  integrate  environmental  and  economic  information  in  a  common,  comprehensive  and 
coherent way to measure the contribution of the environment in the economy and the impact 
that  economic  activities  may  have  on  the  environment.  The  system  provides  a  number  of 
methodological  options,  including  the  assessment  of  natural  assets  or  methodologies  for 
assessing  natural  and  environmental  services.  It  also  establishes  indicators  and  statistical 
methods to measure these interactions. What this system was not intended for was to establish 
the optimal use of the environment for economic uses, but to obtain through the combined use 
of different measures, a balance between human and environmental needs. Since there is no 
general consensus on how to incorporate environmental accounting in national accounts, the 
SEEA recommends the use of satellite accounts that integrate environmental aspects without 
changing deeply traditional accounting systems. These accounts can focus on different natural 
assets, as for instance water (i.e. water accounts). 

Some MS have incorporated in recent decades satellite water accounts without overloading or 
distorting  the  central  accounting  system.  These  accounts  provide  expanded  information  on 
water  issues  which  are  considered  to  have  a  special  social  interest,  using  complementary 
concepts,  expanding  the  information  on  their  specific  relationship  to  human  activities, 
associate  databases  and  identify  potential  gaps  in  them.  This  technical  guidance  document 
focuses on the development of physical water accounts or water balances, which constitutes 
the  first  step  towards  deeper  economic  accounting.  These  refer  to  category  3  of  the  "Asset 
Accounts" of the SEEAW as indicated in Box 1.  

The  development  of  water  quantity  assessment  frameworks  focusing  on  water  balances  or 
asset accounts (which use hydrological information), or incorporating additional elements and 
economic  information  related  to  water  using  concepts  (physical  supply  and  use  accounts, 
hybrid and economic accounts), have been identified as a useful tool for guiding water policy 

5 

 
 
 
and  management  at  different  decision  making  scales,  in  particular  with  regards  to  the 
quantitative management and efficient allocation of water resources2. 

the  activities  of 

the  UNESCO-IHP  programme 

At global scales, several initiatives aim at developing water resources assessments and water 
(UNESCO’s 
balances,  such  as 
Intergovernmental  Scientific  Cooperative  Programme  in  Hydrology  and  Water  Resources). 
Under  this  programme,  an  Atlas  of  World  Water  Resources  was  developed  already  in  the 
1970s and guidelines for conducting water resources assessment developed [8]. A compilation 
of  water  balances  has  also  been  produced  by  FAO/AQUASTAT3  and  the  Mediterranean 
initiative  of  BluePlan.  The  World  Meteorological  Organization  (WMO)  Commission  for 
Hydrology (CHy) has also worked on hydrology and water resources assessment4 . All of this 
material is the core of water balances thinking as we know it today. 

At the EU scale, the European Environment Agency has worked in recent years on physical 
water  balances  at  catchment  scale  [9],  with  specific  efforts  being  put  in  developing  an  EU 
wide  physical  water  assets  account  database  and  assessing  the  relevance  of  integrating  the 
degradation of the natural capital in water (economic) accounts. Eurostat has also worked on 
collecting  data  (hydrological  and  economic  information)  to  feed  the  development  of  water 
accounts under the SEEAW [10] framework at administrative levels (country, NUTSII).  

Physical water balances  can also help support the development of River Basin Management 
Plans  by  providing  a  coherent  framework  to  cross-evaluate  the  information  on  drivers, 
pressures and impacts on water quantity (including the coherence between water abstraction 
and water recharge, water flows between water bodies/catchments, storage changes over time, 
etc.) and providing a sound basis to the quantitative management of water resources. Though 
they  can  be  applied  as  such,  water  balances  are  usually  linked  to  models  for  simulating 
different  components  of  the  balance  and  different  water  management  scenarios  in  order  to 
assess (ex-ante) their potential impact on water use, demand and availability, or to learn (ex-
post) from  the effectiveness  of past  efforts and applied measures to  respond to  drought  and 
water scarcity.  

Today,  water  balances  are  not  systematically  applied  as  an  integrated  component  of 
sustainable  water  resources  management  in  individual  river  basins  and  catchments  facing 
imbalance conditions. Due to the importance of quantitative management of water resources 
on  the  imbalance  between  water  availability  and  water  demand  and  of  water  scarcity  and 
drought, both in ecological, economic and financial terms, MS and the European Commission 
(EC)  agreed  to  develop  the  current  Guidance.  This  document  focuses  on  the  application  of 
water  balances  (also  known  as  Water  Budgets)  for  supporting  River  Basin  Management 
planning processes and the implementation of the WFD in the EU.  

2 The OECD encourages policy makers to engage in a water allocation reform when competition for water uses 
is  increasing.  This  entity  has  developed  a  “Health  Check”  for  water  resources  allocation  for  a  proper 
understanding  and  assessment  of  the  availability  of  water  resources  (surface  water,  groundwater  and 
alternative  sources  of  supply).    (OECD,  2015.  Water  Resources  Allocation:  Sharing  Risks  and 
Opportunities) 

3 See http://www.fao.org/nr/water/aquastat/main/index.stm  
4 http://www.wmo.int/pages/prog/hwrp/index_en.php 

6 

 
                                                 
1.2.  A guidance: what for? 

The  main  objective  of  this  guidance  is  to  support  the  development  and  use  of  water 
balances  at  the  river  basin  and/or  catchment  scales  in  the  context  of  the  EU  Water 
Framework  Directive  (WFD)  implementation,  as  pre-requisite  to  sound  and  sustainable 
quantitative management of water resources. A water balance is based on mass conservation. 
It  reflects  that  the  rate  of  change  in  water  stored  in  a  hydrological  unit  (e.g.  catchment)  is 
balanced  by  the  rate  at  which  water  flows  in  and  out  of  the  unit.  In  the  medium  term,  the 
application  of  water  balances  will  support:  integrated  water  resources  management  and 
decision-making at different scales; a critical review of current water allocation mechanisms 
between and within water use sectors; the definition of policy (water quantity) targets; and the 
drafting  and  adoption  of  measures  that  account  for  the  (quantitative)  sustainability  of  water 
resources.  In  the  medium  term,  the  initiative  will  contribute  to  the  achievement  of  the 
environmental objectives of the WFD and will deliver wider socio-economic benefits. 

Box 1. Water balance or water account?  

‘Water  Balance’  in  this  guidance  is  defined  as  the  numerical  calculation  accounting  for  the  inputs  to,  outputs  from,  and 
changes in the volume of water in the various components (e.g. reservoir, river, aquifer) of the hydrological cycle, within a 
specified hydrological unit (e.g. a river catchment or river basin) and during a specified time unit (e.g. during a month or a 
year), occurring both naturally and as a result of the human induced water abstractions and returns.  

‘Water Accounting’ integrates physical (hydrological) and economic information related to water consumption and use, to 
achieve  equitable  and  transparent  water  governance  for  all  water  users  and  a  sustainable  water  balance  between  water 
availability, demand and supply. Standard water accounting frameworks have been developed by various organizations, such 
as  the  United  Nations  Statistics  Division  (UNSD),  the  Food  and  Agriculture  Organisation  (FAO),  the  International  Water 
Management  Institute  (IWMI),  the  Australian  Government,  etc.  The  UNSD  has  proposed  a  conceptual  water  accounting 
framework called System of Environmental Economic Accounting for Water (SEEAW) [10] for the organization of physical 
and economic information related to water using concepts, definitions and classifications, describing the interaction between 
the economy and the environment. The SEEAW comprises the five categories of accounts: (1) physical supply and use and 
emission accounts (hydrological data on the volume of water used and discharged back into the environment by the economy, 
as well as the quantity of pollutants added to the water); (2) hybrid and economic accounts (linking the physical information 
recorded in the previous category with monetary supply and use information); (3) asset accounts (they measure stocks and 
their changes due to natural causes, such as precipitation, evapotranspiration, etc., and human activities, linking thus water 
abstraction  and  return  to  the  availability  of  water  in  the  environment);  (4)  quality  accounts  (stock  of  water  in  terms  of  its 
quality); (5) valuation of water resources.  

In the context of this guidance document, category 3 of the ‘Asset Accounts’ of the SEEAW are aligned with the concept 
and  components of the ‘Water Balance’, although some discrepancies  might exist in the definitions and in the scales of 
application of both frameworks (see Annex III for further information). 

The  guidance  aims  primarily  at  supporting  water  and  river  basin  managers  in  EU  MS  in 
establishing  and  applying  water  balances  as  essential  tools  for  the  effective  management  of 
water  resources.  The  guidance  document  and  proposed  mechanisms  reflect  flexibility  in 
incorporating  and  taking  into  account  local  conditions  and  specificities.  It  should  also  raise 
awareness  on  the  different  inter-connected  facets  of  the  quantitative  management  of  water 
resources  for  key  stakeholders  involved  in,  or  contributing  to,  participatory  planning 
processes  at  different  management  scales  (in  particular  the  catchment,  river  basin  and  river 
basin district scales). As water balances are more systematically applied at these management 
scales, they will further:  

  Enhance  Europe-wide  (comparable)  knowledge  on  the  state  and  quantitative 
management of water resources (based on data held by the MS). This knowledge will 
in turn facilitate and contribute to on-going and future Pan-European initiatives such 
as: (1) the mapping of the Europe-wide state of water resources by DG Environment, 
as a contribution to the evaluation of the effectiveness of current water policies; (2) the 

7 

 
development  of  water  balances  by  the  European  Environment  Agency  (EEA)  as  an 
input to the State of the Environment report; 

  Facilitate MS WFD reporting to the European Commission on the quantitative status 
of groundwater resources and on the abstraction pressures on surface and groundwater 
bodies.  It  will  also  facilitate  the  preparation  of  MS  responses  to  the  EEA  (WISE-
SoE#35) and Eurostat (JQ on Inland Waters and REQ) water-related questionnaires on 
water resources availability, abstraction and use; 

  Support  the  ex-ante  assessment  of  possible  future  water  policy  scenarios  by 
individual  MS,  or  at  the  EU  level  in  the  context  of  the  hydro-economic  modelling 
platform currently developed by the DG Joint Research Centre (JRC) [11].  

5 The  new code for Water quantity reporting is WISE  SoE#3 (http://rod.eionet.europa.eu/obligations/184). See 
http://forum.eionet.europa.eu/nrc-eionet-freshwater/library/wise-soe-reporting-2013/water-quantity-

also: 
reporting-2013  

8 

 
 
                                                 
Box 2. What are the benefits you, as water and river basin managers, can get from applying water balances? 

By applying water balances, you will…. 

  Better understand whether your water resources are “at quantitative risk” - or not! and the gap to good status that need 

to be filled with measures. 

 

Support the identification of drought and water scarcity situations. 

  Contribute  to  the  development  of  a  common  EU-wide  knowledge  with  coherent  and  comparable  data,  harmonized 

definitions  and  common  understanding  of  the  relevant  assessments  when  applying  water  balances  within  the  general 
proposed framework of this guidance document. 

  Have a good overview of the spatial and temporal variability of water resources, under current and future (scenario 

building) conditions in order to design, identify or bridge the gaps of appropriate allocation schemas. 

 

Identify  “where best to target efforts” (be it identifying areas where action is needed due to existing or future water 
stress, reducing abstraction from a given use, focusing on runoff, increase storage, develop reuse, etc.) when selecting 
measures for improving the quantitative state of water resources. 

  Have a solid base for additional water resources assessment and management at various scales:  runoff estimation, 

groundwater  recharge  potential,  nitrates  mass  balance,  water-energy  nexus,  e-flows  and  GES  determination,  input  to 
real-time analysis, operation and forecasting. 

Provide  a  coherent  framework  for  combining  and  structuring  hydrological  and  socioeconomic  information  on 

climate, water resources in different compartments, water uses (abstraction, discharge…), etc.  

Facilitate the identification of priority water quantity priority data flows and identify possible “data gaps”. 

Provide  a  common  platform  for  building  a  “shared  understanding”  of  issues  between  stakeholders  and  different 

water users, as all are represented by one or more components of the water balance. 

Facilitate reporting (EC, EEA, Eurostat), including a better structuring of the water-quantity related information for the 
WFD RBMPs in the next cycle. 

Provide sounder arguments as part of communication and awareness raising. 

 

 

 

 

 

1.3.  Guide to the reader 

In addition to the present introductory chapter, the guidance is organised in 6 chapters: 

  Chapter  2  -  Key  components  of  water  balances  presents  the  basic 
components  of  the  standard  hydrological  cycle  and  the  main  equations  that 
govern the hydrological cycle. It constitutes the basis of water balances. 

  Chapter  3  -  Key  issues  in  developing  water  balances  addresses  the  main 
methodological  issues  encountered  when  developing  water  balances.  These 
include issues related to: time and spatial scales; data sources and availability, 
and related uncertainty; approaches for incorporating ecological needs; etc. 

  Chapter 4 - Applying water balances in practice presents examples of current 
water balance applications in European MS, illustrating in particular available 
tools that are or have been mobilised for supporting the establishment of water 
balances. 

  Chapter  5  -  Using  water  balances  for  supporting  water  management 
illustrates  how  water  balances  can  help  addressing  water  management 
decisions at different stages of the river basin planning process.  In particular: 
supporting 
the  Programme  of  measures  (PoM); 
highlighting  water  resource  allocation  potentials  and  challenges;  adapting 

the  development  of 

9 

 
 
proposed measures for addressing water quantity issues accounting for climate 
change or resource efficiency improvement.  

  Chapter  6  -  Expanding  the  physical  water  balance  for  addressing 
complementary  water  management  issues  suggests  possible  expansions  of 
the basic water balance  framework so other  water management issues can be 
addressed.  Specific  attention  is  given  to  accounting  for  water  quality  issues, 
and  to  linking  water  balance  information  to  basic  socio-economic  indicators 
characterising specific water use sectors.  

  Chapter  7  -  “Recommendations”  summarizes 

lessons  and 
recommendations that originate from the shared collective experience of water 
balance  applications  in  Europe,  highlighting  how  water  balances  can  help 
supporting  the  implementation  of  the  WFD  and  the  achievement  of  its 
environmental objectives.  

the  main 

10 

 
 
2.  KEY COMPONENTS OF WATER BALANCES 

Building  water  balances  helps  to  combine  and  structure  the  key  components  of  the  natural 
hydrological  cycle  (without  human  pressures)  and  the  relevant  inputs  and  outputs  due  to 
human  interventions  (e.g.  abstractions,  returns,  etc.)  into  a  coherent  framework.  The 
following sections explain these different components, identifying the type of information that 
is required for describing each component and developing water balances. It combines general 
information  on  definitions  and  concepts,  with  illustrations  presenting  “how  to  do  it”  in 
practice. Specific attention is given to the choice of temporal and spatial scales, as these have 
direct implications on data requirements and the ease of developing water balances6.  

2.1.  The key components of the hydrological cycle 

The  first  step  in  developing  water  balances  requires  the  assessment  of  the  freshwater 
resources,  accomplished  through  the  quantification  of  the  components  of  the  hydrological 
cycle. The (natural) hydrological balance equation is based on the principles of conservation 
of mass in a closed system: any change in the water content of a given soil volume during a 
specified  period  must  equal  the  difference  between  the  amount  of  water  added  to  the  soil 
volume  and  the  amount  of  water  withdrawn  from  it.    In  its  simplest  form,  the  hydrological 
balance of a catchment is described by the equation: 

IN  = 𝑂𝑈𝑇 ±   ∆𝑆 

[Eq. 1] 

Where IN = inflow of water to the hydrological unit7; OUT = outflow from the hydrological 
unit  and ΔS = change in  storage within the selected hydrological  unit (e.g. catchment).  The 
components  of  [Eq.  1]  are  expressed  in  units  of  volume  per  time  unit,  i.e.  hm3/month, 
hm3/year,  etc.  In  a  system  with  no  external  inflows  from  neighbouring  catchments  and 
territories,  the  water  is  entering  the  system  via  precipitation  (P),  converted  into  evaporation 
(E)  and/or  runoff  (R)  (surface,  subsurface  or  groundwater)  and  associated  storage  (S)  or 
change  in  storage  ΔS  during  the  time  period  investigated,  as  expressed  in  the  following 
general equation: 

P = R + E ± ΔS 

[Eq. 2] 

In  more  detail,  looking  at  the  functioning  of  the  hydrological  cycle  and  the  dynamics  of  its 
different  components  (Figures  1-3.)  during  a  given  time  period,  (P)  reaches  the  soil  surface 
and the vegetation where water can be intercepted and evaporate directly (Ei) or stored (ΔS). 
Water can also infiltrate the soil or directly runoff (Rs) if the amount of rainfall exceeds the 
infiltration  rate  capacity  (rainfall  excess).  The  water  infiltrating  the  soil  goes  to  the 
unsaturated  zone  (ΔSu)  and  recharges  the  ground  water  (ΔSgw).  Groundwater  (Rgw)  and 
unsaturated  zone  water  (Rsub)  can  also  contribute  to  river  flows  as  subsurface  runoff.  The 
roots of vegetation absorb water that is transported to the stomata of the leaves, where it goes 
back to the atmosphere as transpiration (Et). Water can also evaporate directly from the soil or 
from the river (Es). Capillary rise brings water to the soil surface and then water evaporates. 

6 Note also that the definition of the boundaries of the system which hydrological functioning will be captured in 

the different components of the water balance is crucial when developing water balances. 

7 The unit of analysis could also be a hydrogeological unit, since the boundaries of the catchments often do not 

coincide with the boundaries of the underlying groundwater bodies. 

11 

 
 
 
                                                 
These  elements  and  their  inter-relations  are  illustrated  in  Figures  1  and  2,  and  lead  to  the 
following formulation of equation 2: 

P = Rs + Rsub +Rgw + Es + Ei + Et ± ΔS 

[Eq. 3]  

Where: 
P: Precipitation [hm3/ time unit] 
R: Runoff (s: surface, sub: subsurface, gw: groundwater) [hm3/ time unit] 
E: Evaporation (s: surface, i: interception, t: transpiration)[hm3/ time unit] 
ΔS: Change in storage over time[hm3/ time unit] 
*Note: 1hm3 = 1 million m3 

The  runoff  process  contains  three  components  [11]  [12]:  (a)  the  overland  flow,  (b)  the 
interflow,  and  (c)  the  baseflow.  The  overland  flow  (also  known  as  surface  runoff  Rs  or 
Hortonian  overland  flow)  occurs  when  the  rate  of  precipitation  (or  snow  melt)  exceeds  the 
interception requirements  and the infiltration rate  /  capacity. The excess  water  then starts  to 
accumulate  in  small  surface  depressions,  and  gradually  forms  an  overland  downslope  flow, 
influenced  along  its  course  by  tension  and  friction.  Eventually,  as  rainfall  continues,  this 
overland flow culminates downstream in the river (or a topographic depression) through the 
main  and  secondary  drainage  network  of  the  catchment,  eventually  contributing  to  the 
streamflow. The interflow (or subsurface runoffRsub) is the portion of infiltrated rainfall that 
moves laterally through the upper soil layers until it reaches the stream channel. It depends on 
the  physical  characteristics  of  the  catchments  and  the  spatiotemporal  characteristics  of  the 
rainfall  (e.g.  in  thin  soils  overlaying  impermeable  layers  interflow  is  prominent,  whereas  in 
permeable  soils  the  downward  infiltration  dominates)  [11].The  baseflow  (or  groundwater 
runoff Rgw) is  the portion of infiltrated rainfall that reaches the groundwater table and then 
discharges  into  streams.  It  responds  much  more  slowly  to  rainfall  and  does  not  fluctuate 
rapidly. In areas with seasonal rainfall baseflow gradually builds-up, peaking towards the end 
of the wet season.  In areas of limited outflow, the baseflow may be intermittent or seasonal 
[11].The  overland  flow  together  with  the  interflow  are  the  two  components  of  the  Direct 
Runoff  [11].  The  Direct  Runoff,  combined  with  the  Baseflow  Runoff  (resulting  from 
groundwater runoff and/or delayed subsurface runoff) contributes to the Total Discharge (or 
streamflow) as illustrated in Figure 1. 

Estimating  the  different  storage  capacities  of  a  water  system  or  catchment  is  key  to 
understanding and analysing the overall hydrological process. Water storage can occur in soil, 
groundwater, lakes, rivers, snow and glaciers or vegetation. Storage in vegetation is relatively 
limited compared to the total volume stored, although it can have a significant impact in the 
short-term on vegetation water use. But other forms of water storage, such as in soils, lakes, 
glaciers,  groundwater  or  snow  (in  particular  in  Nordic  and  mountainous  conditions)  are 
important to study, especially in a context of land use change. Climate change can impact any 
of the components of the water balance, in particular precipitation and storage. For long-term 
averages  under  assumptions  of  stationary  conditions,  it  is  often  assumed  that  the  change  in 
storage for an annual time step is marginal and equal to zero, yet this is not applicable at the 
monthly scale. 

The  quantification  of  the  components  of  Eq.  3  at  a  given  hydrological  unit  in  a  given  time 
period requires information from monitoring stations. Hydrometeorological networks provide 
information on water flows into, and losses from, rivers, soils, lakes and aquifers, as well as 
on precipitation and evaporation, in selected sites, depending on the design and density of the 

12 

 
 
 
 
 
network. However, some kind of inference is always needed since it is impossible to monitor 
every component at every place, so the water resources assessment of Eq. 3 usually requires 
the use of rainfall-runoff models which are properly calibrated at the control monitoring sites.  

In a natural system with external inflows from neighbouring catchments and territories, Eq. 3 
can be further formulated as follows: 

P + ExIn= Rs + Rsub +Rgw + Es + Ei + Et ± ΔS 

[Eq. 4]  

Where: 
P: Precipitation [hm3/ time unit] 
R: Runoff (s: surface, sub: subsurface, gw: groundwater) [hm3/ time unit] 
E: Evaporation (s: surface, i: interception, t: transpiration) [hm3/ time unit] 
ΔS: Change in storage over time [hm3/ time unit] 
ExIn: External Inflow is  the total  volume of actual flow of  rivers  and groundwater entering 
the hydrological unit of analysis from neighbouring territories/other units [hm3/ time unit] 

In some  cases, there might  be some  amount of  water that  is  lost from the hydrological unit 
due  to  naturally  occurring  groundwater  outflow  to  neighbouring  systems  or  to  the  sea  (i.e. 
outflows  from  the  groundwater  bodies  which  do  not  contribute  to  the  baseflow  but  feed 
neighbouring  systems  or  discharge  directly  to  the  sea).  This  is  common  in  karstic  systems, 
coastal  areas,  islands,  etc.  This  amount  should  be  then  incorporated  in  Eq.  4  as  a  sink 
(External  Outflow)  and  part  of  the  right  side  of  the  hydrological  balance  equation,  but  it  is 
usually difficult to estimate. 

Figure 1. Capturing the key components of the hydrological cycle8 

8ACTeon, 2014 

13 

 
 
 
 
                                                 
Figure 2. Schematic representation of the hydrological cycle [12] 

Figure 3. The runoff process components and their contribution to total discharges [12] 

14 

 
 
 
 
 
 
Box 3. Groundwater considerations 

While groundwater balances could be done separately, these should ideally be done in an integrated way, i.e. for the whole 
natural hydrological cycle.  

To  better  incorporate  groundwater  aspects,  water  balances  should  be  accompanied  by  dynamic,  numerical,  distributed 
physical  based,  groundwater-surface  water  models  (validated  with  measured  water  balance  data).  These  models  should  be 
applied  and  used  for  the  calculation  of  water  balances  in  relation  to  catchment,  groundwater  aquifers  and  impacts  from 
groundwater  abstraction  on  ecosystems,  or  ecological  flows  in  rivers  among  others.  This  type  of  model  may  be  used  to 
determine dynamic changes of the water balance and the complex changes in interactions between abstraction, groundwater 
level, drainage flow, groundwater discharges in space and time that groundwater abstraction will cause [13]. 

Box 4. Investigating the importance of the snowpack in water balances 

Snowpack is an essential part of the water cycle in Northern Europe and in mountainous regions. In particular, the river flows 
of  several  large  Central  European  rivers  depend  partly  on  the  melting  of  the  snowpack  of  the  Alps.  Snowpack  can  be 
considered a water reservoir that: (1) recharges and releases water without human control; (2) has typically a yearly pattern in 
variation  which  affects  the  entire  water  cycle;  and  (3)  is  not  abstracted  for  human  use  and  thus  has  a  purely  natural 
variability. 

Accumulation of snowpack decreases runoff and recharge of other reservoirs during the winter months. On the other hand 
melting of snowpack increases runoff and recharge of reservoirs during spring. Lack of snowmelt can increase possibilities 
for  drought  during  the  spring  and  early  summer.  On  the  other  hand,  rapid  snowmelt  may  cause  floods.  E.g.  in  Finland 
snowpack accumulation is between 10-30 % of yearly precipitation and snowmelt takes usually only one to two weeks during 
spring which often causes spring floods. The warming climate is predicted to increase variation in the snowpack, increasing 
the risks of floods and droughts, and to also affect the timing of the spring snowmelt, leading consequently to change of the 
time (month) of maximum spring runoff in some countries. 

There  are  several  methods  for  assessing  the  snowpack.  In  Finland,  snowpack  data  are  based  on  about  150  snow  course 
measurements (a snow course is a 2 to 4 km long trail through various terrains typical for the area). Measurements are made 
once or twice a month. For days between measurements, daily values of the snowpack are calculated by a model which also 
assimilates  data  from  satellite  remote  sensing.  The  Finnish  Meteorological  Institute  develops  and  provides  snow  water 
equivalent  (SWE)  values  for  the  whole  Northern  Hemisphere.  The  SWE  data  are  based  on  passive  microwave  radiometer 
data combined with ground-based synoptic snow observations. These data are used e.g. to calculate Standardized Snowpack 
Index  (SSPI)  daily  and  nearly  real-time  (one  day  delay)  for  the  whole  Europe  with  25  X  25  km  grid  (refer  to  the  SSPI 
Indicator  Fact  Sheet  [13]).  The  SSPI  provides  information  of  the  relative  volume  of  the  snowpack  in  the  catchment  on  a 
daily, monthly or yearly basis (compared to a given period of reference). The SSPI can be used as drought indicator, e.g. by 
the European Drought Observatory EDO.  

2.2.  From water balance to a detailed list of water quantity related parameters used to 

support policy making 

Flows and storages described previously are due to natural phenomena. Human activities can 
influence  components  of  the  hydrological  balance  equation,  by  removing  (abstractions  for 
water  supply  or  water  transfers)  or  adding  (returns  from  various  users  or  water  transfers) 
certain amounts of water at certain times, or by modifying storage capacity components. Land 
use  changes  induced  by  human  activities,  such  as  increase  in  imperviousness  on  urbanized 
areas or crop patterns in agricultural land, can also have significant influence in the processes 
of soils storage, infiltration and runoff. Water Balances capture the equilibrium in the physical 
system  between  inputs  and  outputs  as  modified  by  the  human  intervention9.  In  general,  the 

9 In terms of inputs and outputs induced by human interventions, only those that influence the equilibrium of the 
physical (natural) system are considered here, as opposed to the overall equilibrium of the water supply system, 
or the equilibrium between availability and demand. In other words, the total volume of desalination or imported 
water is not an input to the natural system since a part is consumed. Only the volume of these components that is 
returned  to  the  physical  system/environment  is  relevant  in  the  Eq.  of  the  Water  Balance.  The  total  volume  of 
desalination, imports and water reuse is of course relevant for the water accounting since it is an input received 
from  economic  units  to  the  water  supply  and  management  system.  This  is  analysed  in  more  detail  in  the 
following sections. 

15 

 
 
                                                 
water  balance  is  described  by  the  following  equation,  building  on  the  basic  input-output 
components of the natural hydrological balance (Eq. 1 and 2): 

INPUTS  =  OUTPUTS  ±  ΔS 

[Eq. 5] 

Where:  

INPUTS = P + ExIn + RET  

OUTPUTS = Eta + Outflow + ABS 

P = Precipitation [hm3/ time unit] 
ExIn = External Inflow is the total volume of actual flow of rivers and groundwater entering the hydrological unit of analysis 
from neighbouring territories/ other units [hm3/ time unit].External Inflow must not be confused with the inputs received from 
economic units (e.g. desalination, water reuse) or the imported water since those are directed for consumption and only a 
part of them is finally discharged to the rivers and groundwater via returns. 
RET = Returned water is the volume of abstracted water, and/or water produced by economic units, and/or imported, that is 
discharged to the fresh water resources of the hydrological unit either before use (as losses) or after use (as treated or non-
treated effluent). It includes water that was directly discharged from a user (e.g. domestic, industrial etc. including cooling 
water,  mining),  and  water  lost  from  the  waste  water  collection  system  (as  overflow  or  leakage).  Internal  transfers  in  the 
hydrological  unit  such  as  artificial  groundwater  recharge  with  source-water  generated  within  (abstracted  from)  the 
hydrological unit, and/or recharges into rivers with source-water generated within (abstracted from) the hydrological unit 
can  be  considered  under  the  returned  water  component  for  the  current  calculation  purposes.  Discharges  to  the  sea  are 
excluded [hm3/ time unit].  
Note: We can further break down Returned water into 2 components: R1 is the amount that is released in-situ and returned 
in  the  system  within  the  time  unit  and  is  practically  a  reduction  in  the  abstraction  part,  while  R2  is  the  volume  that  is 
returned in the system at a next time step or ex-situ (e.g. urban wastewater) and is practically an addition on the resources 
part. Cooling water can fall under R1 or R2 depending on the type of industry and case). 
ETa = Actual Evapotranspiration[hm3/ time unit]. 
Outflow = The total volume of actual outflow of rivers and groundwater into the sea plus actual outflow into neighbouring 
territories  (outside  the  hydrological  unit  of  analysis)  [hm3/  time  unit].  Note:  Environmental  Flow-EF  and  other  Water 
Requirements-WR as defined e.g. by treaties are a part of the Outflow). 
ABS  =  The  total  volume  abstracted  from  the  system,  from  surface  and  groundwater  resources,  intended  for  any  use 
(consumptive, non-consumptive, transfer etc.). Water abstracted for hydropower generation (in-situ use) should be excluded 
from the formulation of the water balance equation, while water abstracted for cooling should be included. 
ΔS = Change in Storage (both in surface water and groundwater as a lumped sum). 
*Water transfers, exported or imported water, are included in Eq. 5 as part of returns and abstractions respectively.  
Water generated from desalination is a “non-natural feature” and thus the full volume of the available desalinated water is 
not considered as an input to the freshwater resources. What is in fact considered an input in this case is the volume of water 
coming from desalination and discharged to the freshwater resources after use. This is incorporated in the Returned water. If 
all of the available desalinated water was considered an input, this would result in a biased water balance equation since 
part of this volume is in reality consumed and thus not available to the natural/physical system. 

As with Eq. 3 and Eq.4 above, Eq. 5 can be further refined reflecting the various components 
of  the  hydrological  cycle  for  both  the  physical  parameters  (e.g.  inflow  can  be  surface  or 
subsurface, evapotranspiration could be from surface or interception or transpiration, storage 
can be surface or subsurface, etc.) and the anthropogenic induced activities (abstraction can be 
separated  to  surface  and  groundwater,  returned  water  before  use10  or  after  use11,  etc.).  The 

10Water  abstracted  from  any  freshwater  source  and  returned  to  a  freshwater  recipient  before  use  refers  to  the 
volume of water lost during transport through leakage between a point of abstraction and a point of use, and/or 
between  a  water  supplier/distributor.  Discharges  to  the  sea  are  excluded.  Evapotranspiration  losses,  or  water 
which occurs during mining or construction activities is not included (EEA – ETC/ICM, 2013.WISE-SoE Water 
Quantity, Data Manual, v3.1) 
11Water abstracted from any freshwater source and returned to a freshwater recipient after use refers to the total 
volume of water discharged after use as treated effluent or as non-treated into freshwaters. Cooling water is 
included.  Discharges  to  the  sea  are  excluded.  Treated  effluent:  effluent  that  has  undergone  treatment  through 
UWWTP or other WWTP. Non-treated effluent: Effluent that has not undergone any wastewater treatment and 

16 

 
 
 
 
 
                                                 
customization of Eq. 5 depends on the objectives and on the scale of the analysis. It is unlike 
that all the refined parameters are needed or are of equal importance in all analyses (i.e. some 
are of low importance or even negligible), and this relates of course to the selected boundaries 
of the unit of analysis. Data availability is also a relevant issue here (i.e. monitoring networks 
are  not  designed  to  measure  all  sub-parameters  of  the  hydrological  balance  but  are  usually 
designed according to specific situations taking into account the hydrological and geological 
background).  For  example,  in  a  small  well-defined  catchment  (where  its  boundaries  also 
correspond  to  groundwater  divisions),  where  surface  outflow  occurs  via  a  main  river  outlet 
and  groundwater  feeds  the  river  system,  then  outflow  can  simply  be  represented  by  the 
streamflow  and  baseflow  (such  ideal  cases  can  of  course  be  very  rare).  In  other  cases, 
groundwater discharge can be estimated as the groundwater recharge depending on the time 
step and the characteristics of the aquifer. 

Water balances can be expanded and complemented with additional water quantity parameters 
which are relevant to water accounting, water management and policy, such as water use per 
economic sector, alternative water supplies (desalination, reuse), water demands, conveyance 
efficiency and losses, or economic information on the main water users (e.g.  yields, income 
generated, etc.) as indicated in Table 2. The relevance of including or excluding specific water 
components will depend on the key  water management questions that need to be addressed, 
on the importance of quantitative water management issues for a given country/area, and on 
the specificities of the river basin being assessed. Table 2 stresses in particular the importance 
of  three  different  spatial  scales  (from  small  to  large)  which  are  relevant  to  reporting  and/or 
monitoring: site-specific point data which are linked to a specific water body, main aquifers 
(the ones which collectively account for more than 85% of the MS’s or River Basin District 
(RBD)’s  groundwater  abstractions),  catchment/River  Basins  (or  national  part  of  the  RB  in 
transboundary rivers) of a size relevant to the desired analysis requirements. A fourth scale, 
administrative or statistical unit (such as the Nomenclature of Territorial Units for Statistics-
NUTS  or  the  River  Basin  District  -  RBD  is  suggested  as  a  scale  for  aggregation  and 
visualization (or reporting) purposes, as opposed to a primary calculation scale. 

The  different  water  quantity  parameters  are  classified  under  four  main  categories  related  to 
the: hydrological cycle, water balance, water accounts, water management and policy. There 
is  a  clear  rationale  behind  this  escalating  classification.  The  “hydrological  cycle”  group 
comprises  the  physical  parameters  that  are  necessary  to  fully  describe  the  physical  water 
volume  of  surface,  soil,  and  groundwater  resources.  They  span  from  parameters  which  are 
products  of  direct  measurements  (e.g.  streamflow,  groundwater  level)  and  are  essential  in 
identifying  status  and  trends  of  actual  available  resources  and  linking  them  to  Good 
Ecological  Status  (GES),  to  parameters  which  are  products  of  hydrological  rainfall-runoff 
models  (e.g.  evapotranspiration  or  change  in  water  storage)  essential  in  evaluating  the 
availability  side  of  the  balance  equation  or  the  dependency  of  a  given  territorial  scale  on 
external water inflows.  

The  “hydrological  cycle”  parameters  can  be  expanded  into  “water  balances”  by  including 
anthropogenic  components  which  alter  the  physical  balance  (abstractions  and  returns,  as 
shown in Eq. 5). These are key to the identification and quantification of the overall pressures, 
understanding  over-exploitation  or  capturing  the  relative  importance  of  illegal  groundwater 

was  returned  to  the  water  body.  It  includes  water  that  was  directly  discharged  from  a  user  (e.g.  domestic, 
industrial  etc.,  including  cooling  water,  mining),  and  water  lost  from  the  waste  water  collection  system  (as 
overflow or leakage) (EEA – ETC/ICM, 2013.WISE-SoE Water Quantity, Data Manual, v3.1). 

17 

 
                                                                                                                                                         
 
water  abstraction12,  but  can  also  provide  the  information  base  for  the  identification  of 
significant  beneficial  activities  which  could  be  affected  if  the  water  resource  allocation 
policies were to be changed. Water exports are incorporated in the water balance as part of the 
abstractions (i.e. water can be abstracted for use within the territory or for export). The water 
balance  aims  to  represent  the  balance  of  the  natural  system  (focusing  on  the  freshwater 
environment)  and  not  that  of  the  water  supply  system.  Thus,  water  imports  or  alternative 
desalinated water, which are stored in the water supply system are not explicitly incorporated 
as  sources/inputs,  since  a  part  of  them  is  consumed.  Only  the  volume  (of  imports  and 
desalination)  that  is  discharged  to  the  fresh  water  resources  is  of  interest  here,  and  this  is 
incorporated in the water balance through “returned water”. The full volumes of imported or 
desalination  generated  water  are  of  course  relevant  in  water  accounting  and  water  supply 
management since they represent inputs received from economic units to the water supply and 
management system.  

Regarding  water  reuse,  it  has  a  beneficial  impact  since  in  theory  it  reduces  the  volume  of 
abstraction  needed,  but  at  the  same  time  it  reduces  also  the  potential  available  volume  of 
returned flow. It is seen here as an intermediate step in the process and hence not explicitly 
relevant to the water balance, yet relevant to water accounting and water management.  

Returned water is an important component of the water balance, and includes the volume  of 
water  discharged  to  the  fresh  water  resources  of  the  hydrological  unit  either  before  use  (as 
losses) or after use (as treated or non-treated effluent). This water might have originated from 
abstraction, imports, desalination or other economic units’ production.  It includes water that 
was  directly  discharged  from  a  user  (e.g.  domestic,  industrial  etc.  including  cooling  water, 
mining), and water lost from the waste water collection  system (as overflow or leakage).  In 
some  cases  there  may  be  some  “internal  water  transfers”  from  one  water  body  to  another, 
within  the  hydrological  unit  of  analysis.  Although  in  terms  of  overall  equilibrium  of  the 
hydrological  units  these  transfers  may  be  evened  out,  they  need  however  to  be  correctly 
represented  since  they  might  be  significant  for  specific  water  bodies,  and/or  temporal  and 
spatial scale of analysis. Such internal transfers include artificial groundwater  recharge with 
source-water  generated  within (abstracted  from) the hydrological  unit, and/or recharges into 
rivers  with  source-water  generated  within  (abstracted  from)  the  hydrological  unit.  These 
cases,  for  the  purposes  of  the  water  balance  equation  [Eq.  5]  can  be  included  under 
“abstraction”  (for  the  loosing  water  body)  and  “returned  water”  (for  the  receiving  water 
body). Caution is  again  needed here  in how to  correctly represent  these special cases  in  the 
water  balance  (in  order  to  avoid  double-counting)  and  also  how  to  make  it  transparent  to 
water  agents  not  to  infer  anything  about  the  water  use  characteristics  of  those  water  users 
from the water balance equation. The calculation of returned water is challenging, and data on 
conveyance efficiency and losses (although not components of the water balance as such) are 
necessary for estimating the returns.  

Further  on,  the  “water  accounts”  framework  introduces  a  human  dimension  (e.g.  making 
water use per sector explicit, specifying water reuse or accounting for seawater desalination) 
that help identifying pressures on water resources as well as on the water supply, and possible 
mismatches  between  water  availability  and  actual,  potential  or  desired  water  use.  This 

12  Illegal  abstractions  are  important  in  the  water  balance  equation  since,  if  not  incorporated  under  the  total 
volume  of  abstracted  water,  the  equation  can  result  in  a  misleading  equilibrium.  How  to  calculate  them  in 
practice is challenging (e.g. through past data on illegal water use, via satellite data on soil moisture, via proxies 
comparing  existing  registered  abstractions  to  water  demand,  etc.),  and  this  adds,  of  course,  uncertainty  to  the 
water balance accuracy. 

18 

 
                                                 
provides  further  grounds  to  supporting  policy  reforms.  The  “water  accounts”  category  also 
includes  purely  economic  information  on  the  main  users  (e.g.  agricultural  yields,  income 
generated, etc.) linking production values to availability and water use. This could help to link 
the  protection  of  water  resources  to  economic  development,  or  to  identify  possible  barriers 
imposed by existing water imbalances. Finally, the “water management and policy” category 
provides  a  wide  and  comprehensive  view  by  complementing  knowledge  of  the  previous 
categories (hydrological cycle, water balance, water accounts) with additional information on 
conveyance efficiency, losses and water demand for the main users.  It  thus further supports 
the  identification  of  water  conservation  potential  and  improvements  in  water  efficiency,  the 
identification  of  potential  (and  future)  water  stress  (as  a  mismatch  between  availability  and 
demand),  the  evaluation  of  water  supply  sustainability,  or  the  evaluation  of  trends  in  water 
balance resulting from future (baseline) trends in water demand.  

It has to be noted that this list of parameters relevant for water management and policy are not 
exhaustive, but are the most relevant to the water quantity/ water balance aspects. Many more 
parameters are relevant in view of an integrated water planning and management (including 
drought,  climate  change  adaptation,  etc.),  but  are  beyond  the  focus  of  the  current  guidance 
document. 

19 

 
Table 2. Relevance of the water quantity related parameters to different spatial scales and key policy questions [12] 

20 

 
 
 
The  different  components  of  the  “hydrological  cycle”  and  “water  balance”  convey 
information  on  the  state  of  the  inputs  and  outputs  at  reference  times,  and  their  changes  
between  two  different  reference  periods  (generally  at  the  start  and  at  the  end  of  an  annual 
hydrological  cycle).    These  components  are  dynamic  (even  within  the  hydrological  year), 
subject to trends and influenced by the following natural and anthropogenic drivers: 

  Climate change, which has direct consequences on precipitation (amount and timing) 
and on temperature. Temperature and air humidity rates influence evapotranspiration 
and  the  amount  of  precipitation  impacting  surface  runoff  (heavy  rains  leading  to 
increase  in  surface  runoff).  Climate  change  can  also  impact  water  demands  and  the 
reference (natural) conditions of water bodies; 

in  particular  when 

  Water abstraction (linked to water demand) from rivers, lakes or groundwater that 
impacts  on  water  stored  and  on  water  flows  with  contiguous  compartments. 
impacts  evapotranspiration13, 
Agriculture, 
interception  and  percolation.  And  while  changes  in  domestic  water  use  and  industry 
might be more limited in terms of overall quantity “extracted” from the hydrological 
system  in  some  regions,  it  can  lead  to  shifting  water  between  compartments  of  the 
water  balance  (e.g.  abstracting  groundwater  for  drinking  water  supply  that  is  then 
returned via treated effluent discharges to rivers at potentially different locations); 

irrigated,  also 

  Flow  regulation  induced  when  building  storage  infrastructure  for  enhancing  the 
reliability  of  water  supply  or  producing  electricity  can  also  influence  runoff  and 
infiltration  or  increase  ground  water  recharge,  depending  on  the  size  of  the  storage 
built;  

  Land  use  change,  including  urbanisation14,  leads  to  soil  sealing,  increasing  surface 
runoff  and  decreasing  infiltration  and  evapotranspiration,  and  affects  groundwater 
recharge. 

13Actually any change of land-use that results in vegetation change has an evapotranspiration impact 
14See 

http://ec.europa.eu/environment/archives/soil/pdf/sealing/Soil%20Sealing%20In-

example 

E.g. 

for 

depth%20Report%20March%20version_final.pdf 

21 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                 
Box 5. Glossary of the key terms & components of water balances15 
* All the parameters’ units are expressed in volume/time unit (e.g. hm3/time unit) 

Alternative water supplies: Refers to reused water, desalinated water, etc. 

Aquifer sustainability: The safe yield of a groundwater aquifer is the amount of groundwater which can be pumped from an 
aquifer without unacceptable negative impacts on groundwater level and water quality, compared to the pre-developmental, 
virgin situation (Source: Henriksen HJ and Refsgaard JC 2013. Sustainable groundwater abstraction. GEUS report 2013/30) 

Available water resources: That part of water resources that is available for use. The concept is ambiguous, and depends on 
whether it refers to water available for immediate use or freshwater resources available for future development.  

Average year: a year with average (normal) precipitation conditions. 

Change in storage (∆S): Changes in the stored amount of water (>0, if storage is increasing) during the given time period, 
including  river  bed,  lakes,  underground  water  (soil  moisture  and  groundwater)  as  natural  part  of  the  storage  (Snat)  and  in 
regulated lakes or artificial reservoirs (Sart). ΔS can be ignored for long-term averages if it is not feasible to evaluate them, 
but should be evaluated in annual calculations and to be considered in monthly calculations. 

Conveyance  efficiency:  indicates  the  efficiency  with  which  water  is  conveyed  from  source  of  supply  to  the  field.  It  is 
expressed as a percentage or ratio. 

Desalinated water: the total volume of water obtained from desalination processes. 

Dry  year:  a  year  with  lower  than  average  precipitation  conditions.  The  definition  of  what  percentage  of  precipitation 
constitutes a dry year is not universal and depends on the characteristics of a region, river basin etc. 

Ecological flows:  Ecological flows are considered within the context of the WFD as “a hydrological regime consistent with 
the achievement of the environmental objectives of the WFD in natural surface water bodies as mentioned in Article  4(1)”. 
Considering  Article  4(1)  of  the  WFD,  the  environmental  objectives  refer  to:  non  deterioration  of  the  existing  status; 
achievement of good ecological status in natural surface water body; compliance with standards and objectives for protected 
areas, including the ones designated for the protection of habitats and species where the maintenance or improvement of the 
status of water is an important factor for their protection, including relevant Natura 2000 sites designated under the Birds and 
Habitats Directives (BHD) (Guidance Document No. 31. Ecological  flows in the implementation of the Water Framework 
Directive. Technical Report 2015, EC) 

Evaporation losses: Water abstracted from any freshwater source lost during transport through evaporation between a point 
of abstraction and a point of use, between a water supplier/distributor and a point of use or between points of use or reuse. 

Evapotranspiration: Total volume of evaporation from the ground, wetlands and natural water bodies and transpiration of 
plants. According to the definition of this concept in hydrology, the evapotranspiration generated by all human interventions 
is excluded, except rainfed agriculture and forestry. The “actual evapotranspiration” is measured or calculated using different 
types of mathematical models, ranging from very simple algorithms (Turc, Penmann, Budyko, Turn Pyke, etc.) to corrections 
related to vegetal cover and season to schemes that capture the hydrological cycle in detail. 

External Inflow: Total volume of actual flow of rivers and groundwater, coming from  neighbouring territories outside the 
hydrological unit of analysis. 

Freshwater  abstraction  (or  freshwater  withdrawal):  Water  removed  from  surface  or  groundwater  resources,  either 
permanently or temporarily, regardless of any input from water return or artificial recharge. Mine water and drainage water 
are included. Water abstracted for hydropower generation (in-situ use) should be excluded from the formulation of the water 
balance equation, while water abstracted for cooling should be included. Water abstractions from groundwater resources in 
any given time period are defined as total amount withdrawn from the aquifer.  

Leakage losses: It refers to the volume of water lost during transport through leakage between points of use and reuse, after 
the treated effluent leaves the wastewater treatment plant and is transported to the recipients. 

Outflow: Actual outflow of rivers and groundwater into the sea plus actual outflow into neighbouring territories (outside the 
hydrological unit of analysis). 

Precipitation:  Total  volume  of  atmospheric  wet  precipitation  (rain,  snow,  hail,  etc.).  Precipitation  is  usually  measured  by 
meteorological or hydrological institutes. 

Returned water: Volume of abstracted water, and/or water produced by economic units, and/or imported, that is discharged 
to  the  fresh  water  resources  of  the  hydrological  unit  either  before  use  (as  losses)  or  after  use  (as  treated  or  non-treated 
effluent). It includes water that  was directly discharged  from a user (e.g. domestic, industrial etc. including cooling  water, 
mining), and water lost from the waste water collection system (as overflow or leakage). Internal transfers in the hydrological 

15 Extracted from the EEA-ETC/CIM WISE-SoE Water Quantity, Data Manual, v3.1 (2013) and are in line with 
the WEI+ Factsheet terminology. 

22 

 
 
 
                                                 
 
unit  such  as  artificial  groundwater  recharge  with  source-water  generated  within  (abstracted  from)  the  hydrological  unit, 
and/or  recharges  into  rivers  with  source-water  generated  within  (abstracted  from)  the  hydrological  unit  can  be  considered 
under the returned water component for the current calculation purposes. Discharges to the sea are excluded [hm3/ time unit]. 

Reused  water:  Water  that  has  undergone  wastewater  treatment  and  is  delivered  to  a  user  as  reclaimed  wastewater.  This 
means the direct supply of treated effluent to the user. Excluded is wastewater discharged into a watercourse and used again 
downstream. Recycling is excluded. 

Snowpack: Volume of snow accumulated stored over a period which can result (fully or partially) in snow melted water. It 
does not include glaciers, and it is measured at a reference time. 

Surface runoff: Also known as overland flow, surface runoff occurs when the rate of precipitation (or snow melt) exceeds 
the interception requirements and the infiltration rate / capacity. The excess water starts then to accumulate into small surface 
depressions,  and  gradually  forms  an  overland  downslope  flow,  influenced  along  its  course  by  tension  and  friction. 
Eventually, as rainfall continues, this overland flow culminates downstream in the river (or a topographic depression) through 
the main and secondary drainage network of the catchment, eventually contributing to the streamflow.  

Water  accounts:  Water  Accounting  provides  a  conceptual  framework  for  organizing  the  hydrological  and  economic 
information in a coherent and consistent manner. It is the systematic process of identifying, quantifying, reporting, assuring 
and  publishing  information  about  water  in  the  form  of  an  accounting  book,  considering  inflows,  outflows  and  changes  in 
stocks. 

Water balance: Numerical calculation accounting for the inputs to, outputs from, and changes in the volume of water in the 
various components of the hydrological cycle, within a specified hydrological unit and during a specified time unit, occurring 
both naturally and as a result of the human induced water abstractions and returns.  

 In  either  case,  access 
http://www.fao.org/nr/water/aquastat/data/glossary/search.html?lang=en). 

to 

the  water  would  have  a  cost  (FAO  Aquastat  Glossary  online,  available  from 

Exploitable water resources: (or manageable resources) Part of the water resources which is considered to be available for 
development  under  specific  technical,  economic  and  environmental  conditions  (FAO  Aquastat  Glossary  online,  available 
from http://www.fao.org/nr/water/aquastat/data/glossary/search.html?lang=en). 

Water  asset  (according  to  SEEA-W):  Water  resource  assets  are  defined  as  water  found  in  freshwater,  brackish  surface 
water and groundwater bodies within the national territory that provide direct use benefits, currently or in the future (option 
benefits), through the provision of raw material, and may be subject to quantitative depletion through human use. The SEEA-
Water asset classification of water resources consists of the following categories: EA.13:Water resources (measured in cubic 
metres)  EA.131:  Surface  water  EA.1311:  Artificial  reservoirs  EA.1312:  Lakes  EA.1313:  Rivers  and  streams  EA.1314: 
Glaciers, snow and ice EA.132: Groundwater EA.133: Soil water. 

Water  demand:  Water  requirements  of  specific  quality  for  different  purposes,  such  as  drinking,  irrigation,  etc.,  assuming 
that water availability is not a limiting factor. Water demand is theoretical (calculated or estimated) and can correspond to 
current situation or to future socio-economic scenarios. 

Water requirements: Volume of water which must be retained in the catchment (thus not actually available for abstraction) 
in  order  to  meet  different  legal  obligations  (e.g.  downstream  navigation,  environmental  thresholds,  as  defined  in 
transboundary treaties). 

Water Transfer: Refers to imports or exports. Water that enters  or exits the territory of reference through mains or other 
forms of infrastructure.  

Water Use: In contrast to water supply (i.e. delivery of water to final users including abstraction for own final use), water use 
refers  to  water  that  is  used  (consumed)  by  the  end  users  for  a  specific  purpose,  such  as  for  domestic  use,  irrigation  or 
industrial processing (usually the basis for paying fees.) Returned water (at the same place and in the same time period) and 
recycling is excluded. 

Wet  year:  year  with  higher  than  average  precipitation  conditions.  The  definition  of  what  percentage  of  precipitation 
constitutes a dry year is not universal and depends on the characteristics of a region, river basin etc. 

23 

 
 
 
3.  KEY ISSUES IN DEVELOPING WATER BALANCES 

3.1.  Developing water balances…. at the right scale 

There are many challenges linked to information availability and accuracy when developing 
water  balances,  depending  on  the  spatial  and  temporal  scales  at  which  water  balances  are 
applied. While there is no pre-conceived rule for deciding on the “most appropriate” temporal 
and spatial scales at which to develop water balances, this choice will depend on the expected 
use  of  the  water  balance  itself  (how  the  information  will  be  used,  for  which  water 
management  decision)  and  on  the  specific  hydrological  and  water  management  context  (in 
particular existing spatial and temporal variability).  

In terms of the time scale, a water balance is generally established for a sufficiently long time 
period such  as  a  year that corresponds  to  a specific cycle (hydrological  year,  calendar  year, 
wet/dry  season,  multi/annual  period  etc.).  The  variability  of  the  key  variables  of  the  water 
balance  (ref.  to  Eq.  5),  such  as  the  evolution  of  water  abstraction  during  a  given  year,  or 
differences  in  rainfall  patterns  depending  on  seasons,  can  lead  to  choosing  a  smaller  time 
scale such as the month or the week. Similarly, if groundwater resources are very significant 
in  the  basin's  system,  a  water  manager  may  use  larger  time  scales  for  comparison  (i.e.  to 
reflect groundwater recharge flows that may take 10-20 years).  

In some cases, rainfall variability during a single year and variability between years, but also 
variability in water demands from different sectors, can require different water balances being 
developed (in particular when the balance of surface water resources is at stake):  

  For capturing the intra-annual variability of rainfall, in particular when surface water 
is  the  main  water  resource,  two  complementary  water  balances  can  be  developed:  a 
water  balance  capturing  the  overall  water  availability  building  on  inter-annual 
averages; and a water balance with shorter time periods such as a week or even a day.   

  For  capturing  the  inter-annual  variability,  water  balances  building  on  inter-annual  or 
multi-annual  averages  values  can  be  complemented  by  a  water  balance  for  a  dry 
year16.  

The  time  step  selected  for  gaining  a  better  understanding  of  the  functioning  of  the 
hydrological cycle within a given year should be carefully selected based on the central water 
management issues to be investigated in the considered catchment. The influence that changes 
in  the  components  of  Eq.  5  may  have  on  water  management  decisions,  and  the  potential 
solutions that might be eventually proposed. Apart from precipitation, water flows and stocks 
considered in water balances do not have the same time response. For example, the effect of 
reduced  precipitations  (dry  period)  is  quickly  reflected  in  soil  moisture.  But  it  needs  more 
time  to  be  translated  into  changes  in  river  streamflows,  and  even  more  time  to  affect  the 
groundwater  balance.  Figure  4.  stresses  the  time  scales  relevant  to  different  flow 
processes/components  of  the  water  balance.  Even  if  all  processes  occur  at  the  same  time, 
responses in terms of changes in groundwater levels or balance for example are significantly 

16  For  example,  in  Spain,  the  irregularity  of  the  hydrological  regime  and  its  impact  on  water  supply  and 
ecosystems is introduced in the Spanish legislation by the concept of “garantía” (level of service) meaning  the 
maximum acceptable deficit in determined periods throughout a series of years.  

24 

 
 
                                                 
slower (time lagged) and smoother (attenuated) than changes in water precipitation  or water 
demand (two key inputs to the water balance).  

Figure 4. Relevance of timescales to different runoff processes (Source: 
http://ocw.tudelft.nl/courses/watermanagement/hydrology-of-catchments-rivers-and-deltas/lectures/6-flow-paths/ 

With regard to the spatial scale, all processes and flowpaths occur at different spatial scales. 
The  wide  range  of  spatial  scales  considered  for  these  different  processes,  and  the  key 
processes that are addressed in priority when taking water management decisions, should help 
reflecting  the  choice  of  the  most  appropriate  spatial  scale  for  establishing  a  water  balance. 
Building  water  balances  for  very  large  catchment  areas  can  mask  the  variability  of  water 
resources  and  water  demands  within  the  study  area,  and  ultimately  hide  crucial  water 
management challenges. On the other hand, developing water balances for very small water 
units  (e.g.  a  group  of  fields  or  a  municipality  area)  will  not  help  identifying  water 
management challenges that could  be addressed by changes in  water management rules and 
strategies  developed  and  applied  at  the  water  catchment,  river  basin  or  sometimes 
regional/national scales, and that are most relevant to the implementation of the WFD and the 
RBMP process (refer to Chapter 5). 

Thus, defining the correct spatial and time scales at which water balances are established is a 
methodological challenge that needs to consider various elements, which should be supported 
by  robust  knowledge  for  supporting  policy  decisions.  In  particular,  the  requirements  that 
water authorities might have with regards to the required accuracy of water balances must be 
taken into account in this process, so that end-products accommodate their specific needs.  

3.2.  Data sources (quality) and uncertainties 

Data  on  water  flows  and  storage  evolution  are  necessary  to  evaluate  the  water  balance  of  a 
catchment.  Elements  like  rainfall  are  easily  measurable,  yet  for  other  components  of  the 
hydrological  cycle  it  is  difficult  to  obtain  direct  and  accurate  measurements  (e.g. 
evapotranspiration).  Aggregation  and/or  extrapolation  from  point  data  to  areal  data  (e.g. 
precipitation) can be challenging as well,  and representativity issues can arise depending on 
the  density  of  the  point  observations.  Furthermore,  the  availability  of  time-series  of  an 
adequate  length,  and  without  gaps  is  not  always  guaranteed.  Therefore,  modelling  or 

25 

 
 
estimation  is  necessary.  For  example,  storage  evolutions  and  runoff  are,  most  of  the  time 
evaluated,  from  measurable  indicators  or  modelled.  Estimation  techniques  can  introduce 
further errors due to non-harmonised definitions, poor methodology or interpretation, or bias 
occurring in the aggregation of primary datasets from different sources and scales. Error can 
further propagate in simulation models used to represent the salient features of the water cycle 
or mimic the anthropogenic activities (i.e. water abstraction, land use change, etc.), due to the 
inherent difficulty in reproducing the behaviour of a dynamic physical system. 

A key problem in any water balance assessment, as part of a conceptual model development, 
or as a result of inverse optimization of a physical based dynamic groundwater surface water 
model, is  the estimation of potential evapotranspiration (PE). PE is  not  a measured variable 
but  assessed  from  equations  and  formulas.  At  the  catchment  scale,  several  PE  estimation 
methods may prove suitable. Simple methods involving only a few climatic variables may be 
preferred  given  restrictions  in  data  availability  (to  more  complex  formulas  e.g.  Penman). 
Climatic variables generally used are: temperature, wind speed, solar radiation and relative air 
humidity.  Several  types  of  methods  exist  as  for  instance  those  based  on  temperature,  those 
based on radiation or those that combine aerodynamic and energetic approaches. 

In  any  case,  reliable  and  frequent  measurements  are  the  base  of  a  sounder  (less  uncertain) 
water  balance.  Furthermore,  extreme  events  and  climate  change  will  require  adaptation  to 
drought  and  abnormal  rain  patterns  and  this  requires  the  use  of  a  large  series  of  hydrologic 
data in order to make an adaptive management plans. Building a knowledge base and turning 
it into an effective tool requires an important  work over large areas and many  years. It also 
requires  the  development  of  working  relations  and  data  exchange  between  institutions 
representing either impacts on water resources or use of water resources. Thus, it is important 
that  data  collection  personnel  works  in  a  co-ordinated  way  with  those  working  on  water 
resource assessment, so that data continue to be relevant to current problems, adequate for the 
assessments and users can rely on their quality. 

In  a  recent  DG  Environment  initiative  under  the  “Preparatory  Action  on  development  of 
prevention activities to halt desertification in Europe”, water balances following the SEEAW 
methodology were developed in selected pilot river basins17. From 2011 onwards, 10 grants 
have been awarded for implementing activities in the following 12 pilot river basins: Tiber18 
(Italy),  Mulde18  (Germany),  Ali-Efenti18  (Greece),  Vit18  (Bulgaria),  Guadiana19,20  (Spain), 
Jucar21  (Spain),  Segura22  (Spain),  Duero23  (Spain/Portugal),  Arno24  (Italy),  Guadalquivir25 
(Spain),  Andalusian  Mediterranean  Basins26  (Spain),  Tagus27  (Spain/Portugal).  The  exercise 

17Two calls were launched, in 2011 and 2012 (http://ec.europa.eu/environment/water/blueprint/balances.htm). 
18  Assessment  of  Water  Balances  and  Optimization  based  Target  setting  across  EU  River  Basins  (ABOT), 
www.abot.it 
19  System  of  economic  and  environmental  accounts  for  water  in  Guadiana  River  Basin  (GuaSEEAW), 
http://iderm.imida.es/guaseeaw/ 
20New developments in Water Accounts Implementation in Guadiana river basin (GUASEEAW+) 
21 

(HALT-JUCAR-DES), 

Halting 

Basin 

River 

Jucar 

the 
Desertification 
http://www.emwis.org/initiatives/desert-jucar 

in 

22 Accounting System for the Segura River and Transfers (ASSET), http://www.assetwater.eu/ 
23  Duero  River  Basin:  Water  resources,  water  accounts  and  target  sustainability  indices  (DURERO), 
http://138.100.137.130/durero_project_2014/ 
24Pilot Arno Water accounts (PAWA), http://pawa.emwis.net/ 
25 System of Water Accounting in the Guadalquivir River Basin (SYWAG)  
26 Water accounting in a multi-catchment district (WAMCD)  

26 

 
                                                 
stressed  its  usefulness  as  a  knowledge-taking  exercise  that  helps  structuring  all  available 
(scattered) information and data into a coherent framework. It also highlighted key challenges 
with  regards to  the  application of the SEEAW water-asset account  tables, in  particular with 
regard to [16]: the types of data required which in many cases cannot be simply obtained as 
products  of  existing  water  policy  reporting,  but  that  require  the  set-up  of  detailed 
hydrological/water resources management models (e.g. for estimating opening stocks in rivers 
or  exchanges  of  flows  between  the  different  components  of  the  hydrological  cycle);  the 
discrepancies  in  definitions  and  proxies  of  parameters  related  to  water  use  in  particular 
between water use, water needs, water demand, water consumptions; the attention required for 
transforming  data  available  at  different  spatiotemporal  scales  into  the  spatiotemporal  scale 
chosen  for  applying  the  water  balance  (mostly  the  monthly  and  water  catchment  scales);  or 
the current data infrastructure which in many MS does not facilitate the (automatic) feeding of 
data into a water balances-like database. Despite these many challenges, the initiative showed 
that monthly water balances at the catchment scale present a clear added value for better water 
management and seems affordable and feasible. Some methodological lessons, along with the 
presentation  of  the  different  data  used  in  part  of  DG  ENV  pilot  projects  and  in  other  MS 
initiatives are presented in the Annexes of the present guidance document.  

Uncertainty in estimates of the main water balance output indicators is inherent to the water 
balance development  and calculations. Uncertainty is  explained by a  combination of factors 
such as the accuracy of input data and measurements used to estimate key parameters of the 
water balance, or the application of specific estimation  techniques, building  for  example on 
model  simulation,  that  cause  uncertainty  in  the  values  of  parameters  estimated.  While 
eliminating  uncertainty  would  be  impossible,  understanding  uncertainty  becomes  central  to 
the  correct  interpretation  of  water  balance  calculations  so  results  are  adequately  and 
cautiously used for supporting decision making. 

Reliability of water balance estimates will depend on conceptual model development as well 
as  performance  of  a  site  specific  model.  A  good  reference  for  model  performance  is  to 
compare  it  with  uncertainties  of  available  field  observations.  If  the  model  performance  is 
within this uncertainty range we often characterize the model as 'good enough'. But usually it 
is not that simple. Therefore, the decision on what is 'good enough' generally must be taken in 
a  socio-economic  context.  This  implies  that  the  performance  criteria  must  be  discussed  and 
agreed  between  water  manager  and  the  modeller  beforehand.  Reliability  of  water  balance 
estimates  therefore  is  conditional  to  the  amount  of  data  and  hydrological/hydrogeological 
knowledge  available,  the  development  of  the  hydrostrategraphic  model,  knowledge  about 
initial  and  boundary  conditions,  maturity  of  process  description,  temporal  and  spatial 
(precipitation, 
input  data 
discretization,  and  water  balance 
evapotranspiration, abstraction/irrigation etc.). 

the  modelling 

for 

3.3.  Correctly identifying water availability and accounting for ecological needs (links 

to e-flows) 

Water resources  availability as a term is used in  very different  ways, addressing separate or 
combined  water  volumes  that  are  part  of  the  water  system.  Notions  and  indicators  such  as 

27Water 
content/uploads/2014/12/PROTAGUS_WEB_30122014_VINCULOS.pdf 

balances 

Tagus 

Basin 

River 

the 

in 

(PROTAGUS), 

http://evren.es/wp-

27 

 
                                                                                                                                                         
‘natural  resources’,  ‘renewable  water    resources’,  ‘exploitable  water  resources’  are  often 
confused with no clear understanding of differences between these concepts28.  

In most cases, water resources are restricted to the actual volumes of water available for use 
since part of the water resources might be practically unrecoverable due to specific geological 
and  morphological  conditions  (i.e.  deep  aquifers  or  direct  discharges  to  the  sea  in  coastal 
aquifers as illustrated in Figure 5.).  

While  these  might  be  challenging  to  estimate,  environmental  and  other  water  requirements 
that  have  a  legal  basis  (e.g.  specific  water  discharges  defined  at  a  frontier  point  as  part  of 
transnational water treaties) need to be considered when developing a water balance, as these 
can  limit  the  water  available  for  exploitation  and  use  for  consumptive  purposes.  It  is 
recognized  that  the  percentage  of  the  mean  annual  river  flow  or  baseflow  that  needs  to  be 
allocated  to  freshwater-dependent  ecosystems  to  maintain  them  in  good  ecological  status 
should consider the temporal variability of the environmental demand and the seasonal natural 
variations to account for the functioning of river ecosystems. It should also consider aquifer 
sustainability29,  e.g.  impact  on  groundwater  level  and  groundwater  quality  of  related 
groundwater  bodies.  Excluding  this  volume  from  the  available  for  exploitation  water  may 
result in changing the severity level of water quantity status.  

Environmental water requirements for different large European basins or drainage regions are 
presented  in  some  studies  [15],  as  a  percentage  of  the  available  water  required  to  be 
maintained for environmental purposes. These percentages vary (e.g. 40% for Danube, 34% 
for Dnieper, 45% for Elbe, 47% for Oder, 44% for Rhine, 40% for Rhone, 35% for Seine) but 
generally they are around 40%. Of course, these are just some indicative numbers, since the 
percentage required highly depends on the spatial scale of analysis and cannot be generalised 
for all rivers (e.g. in the case of smaller rivers, precautionary assessment often  assumes that 
only 10-20 % of low flow can be impacted by withdrawals).  Returned water (into the same 
hydrological unit where abstraction occurs) can also affect the water resources availability of 
an area. Depending on the water quality and location where the return occurs (e.g. sufficiently 
upstream  so  it  is  exploitable  by  potential  users  downstream  of  the  return  flow  point),  this 
returned  water  volume  can  be  an  important  addition  to  the  hydrological  cycle  alleviating 
potential water imbalance problems downstream, stressing the potential role water reuse could 
play  in  some  river  basins  for  addressing  current  imbalances  in  water  resources.  These  will 
need to be accounted for when calculating the overall balance between water availability and 
water  needs)  of  a  region  or  catchment  to  assess  its  current  water  stress  conditions.  It  is  of 
course  recognized  that  return  of  untreated  or  poorly  treated  water  can  worsen  the  water 
quality and ecological status of a water body, and limit further abstraction for users requiring 
good quality water. 

28  In  the  SEEAW  2012  indicators  related  to  water  resources  availability  are  presented  in  detail  in  Annex  III. 
(United  Nations  Statistics  Division  (UNSD).  2012.  System  of  environmental-economic  accounting  for  water, 
United Nations, New York, 2012). 
29 In Denmark a max 30% of total groundwater recharge to aquifers/bodies is allowed for abstraction. In practice, 
in  many  places  only  50%  can  be  removed  without  impacts  on  groundwater  quality,  when  based  on  detailed 
investigations with analysis of monitoring data. 

28 

 
                                                 
Additional 
Resources (e.g. 
Desalination)  

ECONOMY 

Water Needs (actual, theoretical) 
Water Use 
Water Consumption 

Abstraction  

Return  

WATER RESOURCES 
AVAILABILITY 
(flows and stocks) 

Theoretical 
↓ 
Renewable 
↓ 
Exploitable 
↓ 
Actual use-potential 

↑ 
Environmental Requirements 

Figure 5. The flows of water between the environment and the economy along with relevant 
water scarcity parameters [1] 

29 

 
 
 
 
 
 
 
 
Box 6. Estimation of the Actual Available Water Resources in the Malta River Basin District30 

In small islands and coastal river basins, natural subsurface discharge of groundwater can reach levels of around 50-60% of the 
mean annual recharge to groundwater and is thus an important factor in the water balance calculations. It is one of the main factors 
limiting groundwater availability and its non-consideration has the effect of artificially increasing the 'Available Renewable Water 
Resources' since freshwater lost by this natural process is not available for abstraction and subsequent use.  

Additionally, one should note that the small distance to the coast and other topographical considerations limit the proportion of 
rainwater runoff which can be collected/harvested for eventual re-use. Due to their small size, the proportion of rainwater runoff 
generated in near coastal areas (and thus not recoverable) assumes higher significance compared to bigger continental river basins. 
Similarly  to  subsurface  discharge,  not  taking  this  fact  into  consideration  results  in  artificially  increasing  the  'Renewable  Water 
Resources'. The main impact of these two factors, namely increasing the 'Renewable Water Resources' can result in artificially low 
indices  of  Water  Exploitation  for  these  river  basins  if  not  properly  accounted  for,  which  do  not  reflect  the  reality  which  these 
basins  are  facing.  Considering  data  from  Malta  RBD  as  a  case  study,  deducting  the  natural  subsurface  discharge  and 
unrecoverable surface runoff from the ‘Renewable Water Resources’ (as these volumes cannot actually be recovered) results in a 
better  estimation  of  the  actual  full  use-potential.  The  resulting  water  exploitation  (defined  as  the  ratio  of  abstraction  minus 
returned  water  over  the  actual  full-use  resources)  is  69%  for  the  long-term  average  and  99%  for  the  year  2010,  demonstrating 
conditions of heavy exploitation, as presented below. If these volumes had been considered as available for abstraction, the water 
exploitation ratio value would have been 40% and 55% respectively, illustrating a lower and unrealistic exploitation of the RBD. 

Calculation  of  the  Water  Exploitation  WEI+  for  Malta  RBD,  taking  into  account  the  volume  of  water  resources  that 
cannot actually be recovered. 

Parameter 

Precipitation (P) (hm3) 

Actual Evapotranspiration (ETa) (hm3) 

Renewable  Water  Resources  (hm3)  (RWR  = 
P – ETa) 

Natural subsurface discharge (Qsub) (hm3) 

Unrecoverable surface runoff (Run) (hm3) 

Actual  Available  Water  Resources  (hm3) 
(AAWR = RWR – Qsub – Run)  

LTAA 

174 

105 

69 

23 

6 

40 

2010 

162 

Comments 

97 

assumed at 60% of total precipitation in both cases 

65 

23 

6 

36 

Estimated at  25% of total surface runoff generated 
(initial estimate) 

Total Abstraction (hm3)  

Returned water (hm3)  

WEI+ 

37,5 

43,7 

10 

8 

69% 

99% 

return  from  leakages  -  value  is  reducing  due  to 
leakage program 

WEI+ here is defined as the ratio of Total Abstraction minus Returned water over the Actual Available Water Resources (WEI+ = 
(Abstraction-Returned water) / AAWR) 

30 Source: Data provided by the EIONET NFP of Malta (Malta Resources Authority, Regulation Unit) during the 

EEA Consultation of the WEI+ in August 2012, in Kossida et. al., 2012 

30 

 
  
  
  
  
  
  
 
 
 
                                                 
4.  APPLYING WATER BALANCES IN PRACTICE 

Water  balances  are  not  yet  systematically  developed  and  applied  today  in  each  and  every 
catchment  in  Europe.  Reasons  that  might  explain  this  situation  include:  (1)  the  absence  of 
water stress or water “imbalance” situation (i.e. not all exploitable water being used) in many 
catchments  that  does  not  justify  developing  a  water  balance;  (2)  the  disaggregated  efforts 
made  to  monitor  the  different  components  of  the  hydrological  cycle,  with  no  (institutional) 
mechanism  for  combining  these  into  a  common  (water  balance)  framework  that  could  help 
supporting  policy  making;  (3)  the  lack  of  information  available  for  estimating  the  main 
components of a water balance with sufficient accuracy at spatial and temporal scales that are 
relevant  to  water  management  decisions;  (5)  traditional  water  management  based  on  local 
experience and water level information. 

Still, many water authorities in different MS have experience with the application of (full or 
partial)  water  balances  or  with  assessment  frameworks  that  have  similarities  with  water 
balances.    Depending  on  the  MS,  water  balances  can  be  applied  systematically  (even  if  not 
fully  developed)  as  part  of  the  regular  water  management  activities,  as  ad-hoc  methods  for 
justifying new investments that aim at enhancing water resources or balancing water needs to 
availability, or for supporting the development of new strategies. For example: 

 

 

In Italy, water balances  are  applied by the River Basin  Authorities on their territory 
following  Article  145  of  the  Legislative  Decree  152/2006.  Water  balances  are 
developed on the basis of the indications given by the Ministry of Environment Decree 
of 28th July 2004. 

In  Spain, Royal  Decree  907/2007  on Water Planning  and the Ministerial  Instruction 
ARM/2656/2008  for  implementing  the  WFD  in  RBMPs  requires  the  application  of 
water balances in all basins shared with Portugal and by several autonomous regions. 
This  regulation  defines  the  scope  of  the  basin  water  balance  (resource  studies,  uses 
and  demands,  rules  of  management)  but  also  the  methods  and  tools  that  can  be 
mobilized  for  developing  water  balances.  The  basic  tools  required  by  the  existing 
regulation  include  the  implementation  of  rainfall  and  runoff  models  for  the 
characterization  of  water  resources,  combined  with  allocation  models  for  water 
resources to assess ex-ante the potential impacts of measures proposed for RBMPs. 

31 

 
 
 
 
 
 
 
 
 
Box 7. From Water Resources Assessment  to Water Balance in Spain 

The water resources assessment is performed at RBD level for the whole national territory, with a spatial resolution of 500 m 
(for the most recent updating). Water balances are performed at the level of  “water exploitation systems” (some 150 in total)  
in each RB, being e-flows as previous restrictions and simulating for calculation of water supply reliability for each water use 
(calculation time period is for a long register, and at least from 1980/81 – 2011/12) by means of the DSS AQUATOOL. 

32 

 
 
 
Box  8.  Innovative  methodology  for  generating  input  to  water  balances:  Actual  evapotranspiration  retrieval  from 
remote sensing  

The actual evapotranspiration (ETa) is a key input to water balances, and sometimes a source of uncertainty. Assessing ETa 
from  satellite  images  (MODIS  data)  provides  spatial-temporal  distributions.  The  ground  truth  validation  with  eddy 
covariance, demonstrates the reduction of uncertainties involved. 

33 

 
 
 
 
Box 9. Evolution of the total water usage by consumptive activities and the overall WEI+ in the Segura River Basin, 
South East of Spain. 

The  2005-2008  drought  period  was  triggered  by  extreme  low  rainfall  amounts  in  2005  and  was  followed  by  positive 
anomalies of annual precipitation. The satellite-based estimations of green water consumption in the 4-year period drought 
showed no large reductions, suggesting that this drought period was primary triggered by the reduction of the surface water 
inflows reaching the basin than by a local meteorological drought (Figure 3). 

  Water resource balance is a tool that is regularly used in the Slovak Republic for the 
assessment  of  the  real  status  of  water  use  and  water  resources31.  In  surface  water, 

31 The legislative background for regular assessment of Water resource balance in Slovak Republic can be found at:  

34 

 
 
 
 
 
                                                 
quantitative water resource balance one of the key parameters is the minimum balance 
discharge (representing guaranteed flow, which could be considered as e-flow), which 
is considered on the side of water demands. 

  Water balances in Austria are applied at high spatial and temporal aggregation levels, 
i.e.  nationwide  on  the  basis  of  long  term  annual  averages  (1981-2010)  for 
precipitation,  evapotranspiration,  inflow,  outflow  (rivers  and  groundwater)  and 
abstractions from industry, households and agriculture. 

Box 10.Water balance application in Austria 

Austria  is  abundant  in  water,  only  about  3%  of  the  yearly  available  water  resources  are  used  by  industry,  agriculture  and  the 
private sector. Non consumptive water abstractions  from (and returns to) rivers for hydropower production and cooling are not 
considered. However, hydropower as a renewable source is highly relevant (i.e. about 60%) for the Austrian electricity generation. 
Drinking water supply is 100% covered by groundwater and spring water. Because of an average precipitation of 1,100 mm per 
year (higher in the western alpine parts, lower in the eastern parts) only around 1% of the agricultural land is irrigated. Against 
this  background,  and  after  some  adaptation  measures  to  increase  resilience  and  the  security  of  water  supply  -  taken  due  to 
experiences in the very dry reference year 2003, water scarcity is not a major issue in Austria. 

In the Austrian River Basin Management Plans 2009 and 2015 more detailed assessments for all groundwater bodies and groups 
of groundwater bodies were made looking closely at the sustainably available water resources, the ecological needs of dependent 
surface  water  ecosystems  and  the  amounts of  water  abstracted.  The  assessment  showed  that 100%  of  all  Austrian  groundwater 
bodies and groups of groundwater bodies are in good quantitative status.  

 

In Poland, water resources per capita index get one of the lowest value in Europe, i.e. 
1.8  ths.  m3.ca-1.year-1  (Central  Statistical  Office  of  Poland,  2014).  Moreover,  water 
resources are characterized by considerable temporal and spatial variation. Therefore, 
water  balance  calculations  were  introduced  in  Poland  in  the  1970s.  Comprehensive 
methodology for water balances was developed in the 1990s, and was updated in 2008 

 

 

 

Act. 364/2004 Coll. - Water Act, § 6 Water balance  - mentions two parts of water balance: hydrological balance and water resource 
balance. "Water resource balance compares the requirements for the abstractions from surface waters and groundwater and discharges 
of waste waters and special waters with the available amount of water and its quality and it assesses the impact of the discharging of 
waste waters and special waters on the quality of available amounts of water."    
Implementing  regulation  of  Water  Act.  Regulation  of  Ministry  of  Agriculture,  Environment  and  Regional  Development  of  Slovak 
Republic No 418/2010 about execution of some provisions of Water Act, where in §19 Water resource balance – there is more detailed 
description  of  Water  resource  balance,  its  inputs  and  outputs,  mentioning  that  it  is  being  elaborated  for  the  purposes  of  Water 
management plans of Slovakia, according to the approved time schedule using approved procedures. 
Act 201/2009 Coll., about state hydrological and state  meteorological service. §4  - where  Water balance is listed as one of the main 
tasks of the State hydrological service. 

35 

 
 
 
                                                                                                                                                         
take 

for  the  purpose  of  WFD  implementation,  development  of  RBMPs  and  PoMs.  Water 
balances, defined as  a comparison of water resources and demands of water users in 
terms of water quantity and quality, have been developed in Poland at several spatial 
scales:  water  regions,  groundwater  balance  units  and  river  catchments  indicated  in 
RBMPs as being at risk of not achieving good status. Water balances are calculated by 
simulating  water  allocation  between  various  users.  They 
into  account 
requirements  of  aquatic  and  water  dependent  ecosystems,  relationships  between 
surface  and  groundwater  as  well  as  impacts  that  hydro-technical  structures  have  on 
surface  water  resources.  Simulations  are  undertaken  usually  with  a  time  step  of  10-
days for river catchments and for water regions they are performed on a monthly basis. 
Input  data  for  such  balances  consist  of  multi-annual  time  series  of  river  flows  and 
demands  of  water  users  or  ecological  flow  requirements.  However,  demands  of 
agricultural  users  (fish  ponds,  which  form  an  important  part  of  water  demands  in 
Poland, and irrigation) are modelled simultaneously with water allocation simulations, 
as they depend on previous water supplies. Influence of groundwater abstractions on 
the base flow component is accounted for by appropriate corrections applied to river 
flows  within  a  given  balance  cross-sections.  Water  allocation  is  based  on  the 
predefined priorities of water users, where basic environmental flow requirements are 
the  most  important  in  the  hierarchy.  The  degree  of  implementation  of  water  supply 
tasks  is  assessed  in  terms  of  time  or  volumetric  reliability.  Water  balances  are 
computed  for  several  scenarios  that  consider  different  water  demands,  i.e.  reflecting 
water license agreements  and the level  of current  (or future)  water use,  more or less 
stringent  requirements  for  aquatic  and  water  dependent  ecosystems,  various 
operational  regulations  for  existing  (and  planned)  hydro-technical  structures  or 
alternative  hierarchy  in  water  use.  Such  analyses  help  to  identify  impacts  that 
economic development may have on water resources, as well as  allow assessment of 
the effects  of proposed  mitigation measures. They  help  to  identify the  best  solutions 
and  minimize  potential  conflicts.  For  water  management  policy,  the  most  valuable 
outcomes from the water balance simulations are that they detect a mismatch between 
water  resources  and  demands,  i.e.  they  identify  conflicts  between  environmental 
requirements and demands of water users or identify conflicts between different water 
users.  Results  of  water  balance  calculations  form  a  basis  for  defining  priorities  and 
restrictions  for  water  use  within  river  catchments,  issuing  of  water  licenses, 
formulating/updating operational regulations for hydro-technical facilities and drafting 
PoM. 

In  Denmark,  water  balances  are  applied  routinely  as  part  of  3Da  3-Dimensional 
geological and hydrological mapping of groundwater aquifers to identify groundwater 
protection areas. A national hydrological model (DK model) is applied as part of WFD 
implementation and River Basin Management Planning, including inverse calibration, 
where water balance criteria are included in the optimization. 

In  order  to  protect  ecological  river  discharges  and  to  avoid  overuse  of  groundwater 
resources, quantitative water balances were introduced in Hungary in the 1960s. For 
surface  and  groundwater  resources,  separate  water  balance  methodologies  were 
developed  with  no  attempt till the 1990s to  connect  and harmonize them. The WFD 
gave  new  impetus  to  methodological  developments,  especially  to  account  for  and 
quantify  the  surface-groundwater  interactions,  to  incorporate  groundwater  dependent 
ecosystems (GDEs), and to better handle ecological discharges (see Box 10 below). 

 

 

36 

 
 
Box 11. Applying water balances in Hungary 

Surface water 

Due  to  topographic  reasons,  the  reservoir  storage  capacity  in  Hungary  is  relatively  low,  the  surface  water  resources 
available for withdrawal are mostly limited to the actual flow within the rivers. Water stress usually occurs in July and 
August  when  low-flow  coincides  with  maximum  irrigation  water  demands.  Consequently,  the  water  balance 
methodology was focusing on this summer low flow period and the concurrent water usage. For practical reasons, the 
time scale of the water balance was chosen to be 1 month and the critical surface water resources were identified as the 
80% of August’s daily flows (or the 80% of August’s average flows). Water resources are determined  every ten years, 
from  daily  discharge  time  series  of  the  previous  30-years  period,  in  compliance  with  WMO  guidelines.  Ecological 
discharges are either established by specific ecological  and hydrological on-site analyses, or identified by 60% of the 
quantity of the critical surface water resource of the given river section. 

From a hydrological point of view these low flows should be considered as part of the baseflow and as such, are mainly 
of subsurface origin. Two types of water balance are calculated: 

 

 

Surface  water  balance  of  the  permitted  water  usage:  long  term  water  resources  compared  to  permitted  water 
withdrawals  and  discharges,  providing  information  for  water  management  policies  and  for  the  permitting 
procedures; 

Surface water balance of the actual water usage: water resources compared to actual water usage in a given year; 
informing water managers at the operational level. Currently, the actual balance is also based on the same long term 
water  resource  values,  although  there  is  a  research  project  to  be  launched  to  estimate  the  actual  runoff  using 
hydrological models. 

In both cases one of the purposes of the water balance that must be checked, is to ensure that water withdrawals do not 
exploit the ecological discharge. 

Groundwater balance 

Depending on the geographical scale groundwater balance calculations either rely upon small scale hydraulic modelling 
or  on  larger  scale.  In  water  accounting  calculations  are  carried  out  on  each  of  the  groundwater  bodies  of  a  region. 
Groundwater resources were re-assessed for the 1st River Basin Management Plan in 2004-2008, based on observations 
of the 1991-2000 period, taking into account the interaction between different groundwater bodies, the interaction with 
the surface waters (primarily in the form of the baseflow component), and the constraints imposed by the preservation of 
the GDEs. For each (group of) groundwater body the exploitable amount was set, beyond which withdrawals might have 
severe environmental effects or damage to other groundwater uses. 

The  temporal  scale  of  the  groundwater  balance  is  1  year,  and  elements  of  the  water  household  calculations 
(precipitation, evapotranspiration, in- and outflow, withdrawals, etc.) are expressed as volume for one year. National and 
regional scale water balance calculations are routinely carried out every year, in order to effectively manage resources. 
Re-validation of the withdrawal  limits are generally carried out  every ten  years, and regional changes in groundwater 
heads are monitored continuously. Data on annual and monthly groundwater extractions are collected every year by the 
regional water directorates. 

Also, many national- and EU-funded research projects addressing water scarcity in general, or 
sectoral (irrigation in particular) water use in water scarce regions, rely on the development of 
water  balances  (see  Annexes  for  illustrations  of  applications  of  water  balances  in  MS  and 
within EU-funded pilot projects).  

Many  tools  and  methodologies  exist  to  support  the  development  and  application  of  water 
balances.  Existing  hydrologic  computer-simulation  models  that  help  understanding  the 
hydrology  of  watersheds,  rivers  and  aquifers  are  developed  on  water-balance  principles  for 
estimating  responses  of  the  water-balance  to  changes  in  internal  (land  surface)  or  external  
(rainfall) stressors. Depending on their level of complexity, these models provide an overall 
water balance for a (management) unit, or capture the processes that drive water within this 
unit.  Their application at the watershed scale to support watershed management and planning 
helps predicting stream discharges at the mouth of a basin on the basis of rainfall, snowmelt, 
evapotranspiration,  exchanges  between  groundwater  and  transfer  of  water  within  the  river 
network.  

Also  practical  stepwise  implementation  processes  have  been  elaborated  by  different 
authorities  in  order  to  adopt  flexible  approaches  that  better  account  for  water  management 
challenges  and available information.  Box 12 presents a series of practical steps that can be 

37 

 
followed  for  supporting  the  elaboration  of  water  balances  in  different  countries  and  river 
basins. 

Box 12. A stepwise process for developing water balances 

Step 1 – define the scope of your water balance (system boundaries, spatial and temporal scale …). 

Step  2  –  Identify  the  main  components  (constraints  and  pressures)  of  the  water  balance.    For  example,  abstractions  and 
discharges from different uses, downstream targets (different catchments, other countries when the balance is established for 
the national part of international river basins), level and flow water dependent ecosystems, quality of the water (and potential 
changes in water quality for example, saline intrusion), climate change, sea level rise etc.  

Step  3  –  Review  existing  tools  (software,  etc.)  for  developing  water  balances.  Select  an  appropriate  tool  which  fits  your 
purpose and level of analysis. Consider expandability issues in  your assessment of appropriate tools. Identify specific data 
format  requirements  that  the  tool  might  have  that  will  influence  the  type  and  format  of  the  basic  data  that  need  to  be 
collected.  

Step 4 – Collect all relevant data and information on key parameters available in your river basin. 

Step  5  –  Process  data/information  to  estimate  parameters  at  the  right  spatial  and  temporal  scales.  Make  all  assumptions 
transparent. 

Step  6  –  For  parameters  for  which  information  is  not  available,  propose  innovative  methods  for  assessing  proxies  (see 
example in the Annexes to the present guidance) or use estimates from the literature for similar conditions (of soil, water, 
ecosystems, water services…) 

Step 7 – Develop the water balance using the selected tool(s). Calibrate and validate the output. Identify possible incoherence 
and inconsistencies in parameter estimates. Mobilize additional data and expertise, and perform a sensitivity analysis to refine 
parameter values and obtain a coherent water balance. Note: perform these steps for average, dry and wet conditions.  

Step  8  -  Identify  gaps,  priority  parameters  whose  estimates  need  to  be  refined,  and  initiate  studies  for  improving  the 
knowledge base. 

Step  9  – Start using  the  water  balance  for  assessing:  (a)  current quantitative  status  and  significant  pressures;  (b)  historical 
trends  and  possible  increases  in  pressures  and  deterioration;  (c)  future  quantitative  status  and  pressures  under  baseline 
scenario  and/or  climate  change  scenarios;  (d)  the  impact  (effectiveness)  of  individual  potential  measures  proposed  for  the 
RBMP.  

Step 10 – Update the water balance calculations regularly, as necessary. 

. 

38 

 
 
 
5.  USING WATER BALANCES FOR SUPPORTING WATER MANAGEMENT 

This chapter illustrates the application of water balances and their added value in supporting 
the  implementation  of  the  EU  WFD  and  more  efficient  and  optimal  water  management 
decisions. Whenever possible, practical illustrations of “water balances in practice” developed 
to  support water management decisions are presented as  a  source of inspiration, building in 
particular on experiences of MS and studies carried out under European Commission grants. 
Additional  examples  of  the  application  of  water  balances  are  provided  in  annexes  to  the 
present guidance.  

5.1.  Supporting the characterization of river basins and the identification of key water 

management issues   

Water balances can be used at different steps in the WFD planning process, in particular for 
the  characterisation  of  river  basins  and  the  implementation  of  the  WFD  Article  5.  Water 
balances  will  help  to  characterise  in  a  coherent  manner  the  hydrological  functioning  of 
catchments or river basins. Depending on the spatial scale at which they are developed, they 
will help identifying catchments with significant quantitative water management challenges or 
water  bodies  at  risk  of  failing  the  WFD  environmental  objectives,  be  it  under  current 
conditions or when accounting for changes in key drivers (population, agriculture, land use…) 
and (quantitative) pressures that are foreseen under a given baseline scenario. Thus, areas that 
might face situations such as over allocation, non-authorized abstraction and overexploitation 
can be detected.  

5.2.  Supporting the selection of measures for the WFD PoM  

Water  balances  can  help  support  the  selection  of  measures  for  the  Programme  of  Measures 
(PoM) proposed for each river basin district that will improve the quantitative state of water 
resources and achieve a set objective (e.g. the equilibrium between water demand and water 
supply, a set ecological river discharge or a set objective for replenishing aquifers). Potential 
measures  that  can  be  considered  include:  measures  for  reducing  losses  in  water  distribution 
networks  (drinking  water  and  irrigation  water)  [19];  measures  for  increase  water  use 
efficiency;  Natural  Water Retention  Measures (NWRM) that aim at  enhancing the retention 
capacity of soils and aquatic ecosystems [20]; water reuse and recycling; the development of 
desalination  plants,  etc.32  Once  potential  measures  are  identified,  and  their  direct  unitary 
impact  on  water  abstraction,  runoff  or  recharge  established  (e.g.  in  mm  or  cubic  meters  of 
water  saved),  water  balances  can  help  translating  a  change  in  pressure  into  a  change  in  the 
overall water resource balance. This may help quantify the impact of proposed measures for 
water resources,  assess whether the set WFD (quantitative) objective is  met and support the 

32 If the impact of economic instruments such as water tariffs or abstraction charges on the water balance is to be 
investigated, additional information on water demand price elasticity (obtained from econometric or water-
use  behavioural  models)  is  required.  This  information  helps  in  translating  changes  in  water  tariffs  into 
change in water demand (input into the water balance).  

39 

 
 
                                                 
selection  of  the  set  of  measures  necessary  to  reach  the  WFD  environmental  objectives33.  In 
establishing  whether  or  not  proposed  measures  are  appropriate,  it  is  necessary  to  perform  a 
sensitivity analysis on key parameters to assess whether the assessed effects of the measures 
proposed remain sufficient for achieving set WFD objectives. Depending on the outcome of 
these  assessments,  it  may  be  relevant  to  revise  set  objectives  in  the  light  of  improved 
knowledge on the wider environmental, societal and economic consequences associated with 
the achievement of the original objective in accordance with conditions for WFD exemptions. 
It is important to stress that while these steps appear relatively straightforward on the paper, 
practical application remains challenging, in particular as evidence on the potential effect(s) 
of measures is often unknown or known with limited reliability (see Box 12 below).  

Box 13. Sound and coherent water balances required 34 

The Dutch guidance document on cost-effectiveness analyses  was tested in the eastern part of the country, where different 
pilot study areas were selected including the Eastern part of the Rhine river basin district. In this pilot study, water balances 
were developed using data from different provinces, regional water authorities, and municipalities. One of the lessons learned 
from that pilot study was that using information from various sources created problems, because different borders and surface 
areas had been used in different researches. Another problem was with the existing substances. The first balances of polluting 
substances that were also developed showed significant discrepancies that required recalculations in order to perform reliable 
analyses. In particular, the fact that not all internal loadings could be explained properly had significant consequences for the 
reliability of the results (without a proper substance balance, a cost-effectiveness analysis becomes a shot in the dark). This 
pilot  study  led  to  efforts  to  improve  data  and  modelling  on  water  and  substance  balances.  This  significantly  increased 
reliability and usefulness of the various analyses, including of the cost-effectiveness analyses that were performed as part of 
the preparations for the PoM for the WFD and other policies.  

As discussed further below, the information on the potential impact of potential measures on 
the quantitative state of water resources will contribute to the selection of measures, combined 
(as  discussed  in  Chapter  6)  with  wider  environmental  and  socio-economic  consequences  of 
such  measures  that  can  be  combined  into  cost-effectiveness,  cost-benefit  or  multi-criteria 
assessments. 

33 In the WAMCD Pilot Project (see illustration in Annex II), two different and complementary approaches for analysing the effect of the 

 

 

Programme of Measures were proposed.  
A complete set of SEEAW tables has been calculated, taking into account the expected evolution of pressures from human activity and 
the effects of the actions included in the PoM. 
The building of a catalogue of Measures / Lines of Action in terms of their main incidence water account parameters. For each entry, 
the  following  data  are  included:  name;  response  to;  main  incidences  in  physical  accounts;  main  incidences  in  economic  and  hybrid 
accounts; supplier and user; metering; assessment; programme of measures (inclusion or not in the MBA PoM); additional information 
(including relevant regulatory or administrative tools supporting the measure). 

34 For more details: http://publicaties.minienm.nl/download-bijlage/16702/dutch-handbook-on-cost-effectivenes-analysis.pdf 

40 

 
 
 
 
 
 
 
                                                 
5.3.  Target setting and allocation 

Water  balances  can  help  in  evaluating  the  soundness  of  current  water  allocation  between 
water  uses.  In  particular,  they  can  help  identify  where  there  is  insufficient  water  to  satisfy 
simultaneously all of the desired uses of water by economic sectors and provide the desired 
allocation  to  the  environment  as  required  to  meet  WFD  objectives.  The  possible  impact  of 
changes  in  existing  water  abstraction  permits  and/or  allocation  rules  among  economic 
activities on the different components of the water balance can be assessed. Also, the water 
balance can help in establishing overall targets for water abstraction for each individual use so 
the sustainability of water resources is ensured – so the right balance between abstraction and 
recharge  for  groundwater/aquifers  that  support  depending  aquatic  ecosystems  and  surface 
water  bodies  is  achieved,  or  for  ensuring  sufficient  quantities  of  water  are  left  to  river 
ecosystems. And this can lead to proposed adaptations in existing water permits/consents that 
account for the environmental needs of aquatic ecosystems.  

While  an  annual  or  equilibrium  water  balance  can  often  be  sufficient  for  conceptual 
development  and  preliminary  establishment  of  groundwater  abstraction  targets,  finer  time 
scales  that  can  help  in  capturing  part  of  the  river  water  flow  variability  over  shorter  time 
periods are more relevant for supporting the definition of surface water abstraction targets and 
groundwater  abstractions  with  seasonal  variation  (e.g.  irrigation  from  shallow  aquifers 
connected to rivers).  And the definition of water abstraction permits can also consider series 
of  water  balance  that  capture  average  years  and  also  for  below  average  years  and  drought 
conditions. This can help in defining water abstraction permits that account for the variability 
and reliability of water supplies.  

Box  14.  Water  balance  calculations  to  define  acceptable  pumping  rates  in  the  Central  Flemish  Aquifer  System, 
Belgium. 

The  Central  Flemish  Aquifer  System  is  located  in  the  north-west  of  Belgium.  The  northern  part  of  this  aquifer  system 
consists  of  a  sequence  of  sand  and  clay  deposits,  forming  a  phreatic  aquifer  system  with  up  to  three  underlying  confined 
groundwater bodies.  The confined aquifers are heavily used by the (food) industry and by livestock farmers. Horticulture and 
other sectors with less stringent water quality demands often use phreatic groundwater. 

The carrying capacity of the confined groundwater bodies is limited, amongst others because of the presence of brackish to 
saline  water  in  the  north.  Water  balance  calculations  were  performed  to  assess  the  sustainability  of  the  actually  permitted 
pumping rates. These calculations were performed for equilibrium conditions, so that the long-term impact of an exploitation 
regime  on  the  flows  between  different  groundwater  bodies  and  between  ground-  and  surface  water  could  be  assessed. 
Equilibrium  balances  were  calculated  for  several  exploitation  scenarios,  including  a  scenario  without  groundwater 
abstractions and one where all wells extract the permitted rate. 

The  water  balance  calculations  suggest  that  in  natural,  undisturbed  conditions  (no  abstractions)  the  three  confined 
groundwater  bodies  would  receive  an  inflow  from  neighbouring  non-saline  water  bodies  and  generate  an  outflow  to 
neighbouring  more  saline  water  bodies.  This  would  imply  a  steady  freshening  of  the  confined  groundwater  bodies  of  the 
Central Flemish Aquifer System. However, under the current permitted exploitation regime, the water balance calculations 
predict an inflow of water from the more saline regions for two of the three confined groundwater bodies that were studied. 
For the third (deepest) confined aquifer, a small reduction of the outflow towards the more saline region is expected, but no 
change in  flow direction. This  means that the actually permitted exploitation regime  might at the  long run lead to a water 
quality degradation of the upper two confined groundwater bodies. For the third one, there is no urgent risk. 

Groundwater  management in the Central Flemish  Aquifer System aims at reducing the volume pumped  from the confined 
groundwater  bodies,  eventually  by  allowing  an  increase  in  pumping  rate  from  the  phreatic  system.  Increased  phreatic 
abstractions might affect the low flows of the rivers and the availability of surface water during droughts. The water balance 
calculations show that the actually permitted abstraction rates could reduce the outflow of groundwater to surface waters in 
the region by approximately 9% compared to natural base flows. This is well below the generally accepted thresholds for the 
impact of anthropogenic activities on river flows. A limited increase in phreatic pumping rates could thus be acceptable. 

41 

 
5.4.  Adapting to climate change 

Water balances can be used for identifying water deficit areas under climate change scenarios, 
or  whether  climate  change  will  exacerbate  or  limit  current  water  deficits.  Indeed,  as 
mentioned above, climate change impacts water balances directly via changes in rainfall and 
indirectly with temperature changes that affect evapotranspiration. In territories that are very 
dynamic  from  a  socio-economic  point  of  view,  likely  (potential)  changes  in  water  demands 
from  different  economic sectors and changes in  land sealing (due to  urbanization), obtained 
from prospective studies for example, can also be considered. And water balances for future 
situations that simultaneously integrate wider global changes that affect the hydrological cycle 
can  then  be  developed  (e.g.  via  participatory  integrated  assessments  and  scenario 
development) to identify actions that will enhance the resilience of aquatic systems. 

In  the  context  of  WFD  implementation,  water  balances  can  help  performing  the  climate 
proofing  of  the  measures  proposed  in  the  PoM.  Water  balances  can  first  help  assessing  the 
potential  impact  of  different  climate  change  scenarios.  They  can  also  help  performing 
sensitivity analyses on climate-related parameters to check whether measures proposed in the 
PoM remain relevant and (cost-)effective under future climate change scenarios.  

Box  15.  Using  the  STRATEAU  model  for  supporting  the  development  of  climate  change  adaptation  strategies  for 
water35 
Strateau is a water-balance decision-support tool that confronts water resources availability and water demand for different 
uses.  It  relies  on  a  consistent  database  that  combines  structural 
characteristics of territory and observed data. Based on these data, 
Strateau helps assessing the impact of scenarios linked to changes 
in  agriculture,  climate,  demography, 
industrial  uses,  or 
environmental  demand.  The  results  in  terms  of  withdrawals, 
discharges,  consumption,  average  river  flows  and  aquifer  (net) 
recharge  are  presented  at  the  scale  of  administrative  (region)  and 
hydrologic scales (sub-river basin or river basin) units, using yearly 
and  monthly  time  scales.  The  model  includes  two  modules  that 
interact  thanks  to  well-defined  allocation  rules:  a  resource  part 
integrating  a  ground  water  sub-model  and  a  surface  water  model 
and  a  demand  part  combining  an  agricultural  (CROPWAT-based) 
model and generic sub-models for other sectors relying on unitary 
demand, water demand determinant and exogenous parameters.  
The model was used as part of the Explore 2070 project to assess 
the  potential  impact  of  different  climate  change  adaptation 
scenarios on water – comparing the actual situation, a 2070 situation 
under  climate  change  and  other  global  (economic)  changes  and  a 
situation  with  adaptation  scenarios  implemented.  Measures  investigated  included  changes  in  cropping  patterns,  changes  in 
storage capacity, changes in priority allocation rules, etc.  

5.5.  Identifying room for improvement in resource efficiency 

Water balances can be applied in searching solutions/options that respond to (water) resource 
efficiency objectives and for the optimisation of water use per unit of economic output. This 
optimisation can be part of the selection of the measures for the WFD PoM or as part of wider 
resource efficiency strategies developed at relevant decision making scales. When addressing 

35http://www.developpement-durable.gouv.fr/Evaluation-des-strategies-d.html 

42 

 
 
 
 
                                                 
  
water  use  efficiency,  it  is  important  that  efficiency  targets  are  adequately  set  for  the  non-
productive evaporation/loss water to avoid potential negative impacts for downstream waters 
once return flows are accounted for.  

When addressing sustainability issues like  resource efficiency, it is important to account for 
water  and  energy  issues  simultaneously  (i.e.  estimating  energy  required  and  related  CO2 
emissions for different options of water use and allocation) so resource efficiency is assessed 
in its wider context.  

Box 16. Water per unit of economic output and Thermal Power Plant Cooling Water System Choices 

The choice of cooling system configuration is a fundamental aspect of the design of a thermal power plant. While air-cooling 
can be seen as highly favourable from an aquatic ecosystem  perspective (with zero gross and net water demand) as compared 
to  recirculating  tower-cooling  (abstraction  limited  as  compared  to  net  demand)  or  through  cooling  (an  option  that  implies 
significant water abstraction and that can be considered only  where water resource and receiving water sensitivity allows), 
such  a  plant  will  inevitably  have  a  significantly  lower  thermal  efficiency  than  an  otherwise  identical  water-cooled  plants. 
Reduced thermal efficiency implies more use of fuel per unit energy produced, greater emissions to air and greater production 
of waste or by-product per unit energy produced. It is evident that an option which may appear desirable from the perspective 
of the water environment or a water resource manager must also be considered from a much wider environmental and socio-
economic perspective.  

In some sectors, for example thermal power plant, apparent water use efficiency as measured 
by  gross  and  net  m3/unit  product  can  vary  significantly  between  individual  users  whilst 
remaining  consistent  with  the  Best  Available  Technique.  Care  should  be  taken  when 
considering  the  possible  use  of  comparative  data  on  water  use  efficiency  between  users  to 
ensure  comparative  data  are  on  the  same  reporting  basis.  For  example,  different  literature 
sources  use  different  vocabulary  particularly  in  regard  to  ‘consumptive’  water  use,  storage, 
transfer  and  discharge/release.  It  is  recommended  that  the  water  efficiency  of  a  given  user 
lying  outside  a  reported  range  of  peer  group  users  should  be  regarded  as  a  trigger  to 
investigate  the  specific  circumstances  of  that  user,  taking  into  account  the  wider 
environmental  and  socio-economic  circumstances,  rather  than  immediately  making  the 
inference that it is appropriate to set a more stringent water efficiency target for that user to 
bring  it  in  line  with  the  peer  group.      The  investigation  should  be  aimed  at  establishing 
whether or not the particular water use can be regarded as optimal in the light of the specific 
circumstances. 

5.6.  Contributing to informing and reporting on water policy implementation 

The  establishment  of  physical  water  balances  can  facilitate  reporting  to  the  EC  on  the 
implementation of the WFD. At the time of writing, guidance on reporting is being developed 
in  the  context  of  the  CIS  process  (see  the  CIRCABC  site  for  the  latest  CIS  reporting 
guidance36),  the  objective  being  on  providing  concrete  elements  of  information  that  help  in 
understanding  how  the  different  WFD  obligations  have  been  addressed.  Readers  can  take  a 
look at CIRCABC for the most recent version of reporting sheets.  

The establishment of physical water balances at the water catchment scale will also facilitate 
drawing an accurate pan-EU picture to inform EU water policy making and serve awareness 
purposes, as well as streamline reporting and help MS responding to reporting requirements. 

36 https://circabc.europa.eu/w/browse/3eaafe7c-0857-47d4-a896-8022df48d3ba 

43 

 
 
                                                 
Widely  applied,  it  will  help  in  identifying  water  catchments  at  quantitative  risk  –  and  thus 
provide the basis for estimating their relative importance at different spatial scales (e.g. river 
basin district scale, national scale).   

44 

 
 
6.  EXPANDING THE PHYSICAL WATER BALANCE FOR ADDRESSING COMPLEMENTARY 

WATER MANAGEMENT ISSUES 

Once  set,  physical  water  balances  can  be  complemented  with  information  linked  to  water 
quality  or  economics  that  can  help  support  the  implementation  of  the  WFD  and  water 
management decision making at the catchment and river basin scales.  

6.1.  Expanding water balance to account for water quality  

Integrating  water  quality37  more  specifically  into  physical  water  balances  can  help  address 
water  quantity  and  water  quality  issues  simultaneously.  Balances  for  the  input  of  nutrients 
(e.g.  N)  can  be  developed  using  appropriate  assumptions  for  the  storage,  use,  runoff  and 
leaching of nutrients in different soil and water compartments. This can help estimate nutrient 
leaching to the aquifers, and estimate nutrient concentrations in rivers accounting for average 
river flows at a given time scale (e.g. monthly). These concentrations can then be compared to 
target nutrient concentrations so first judgments can be made on pollution risks and on the risk 
of failing achieving the WFD objectives38. Also, water balances can help investigate issues of 
saline intrusion in coastal aquifers that result from the depletion of these aquifers.  

Water balances  can provide information  for  assessing the advective transport  of substances. 
For  some  substances,  reactive  transport  and/or  diffusion  might  have  a  significant  impact  on 
the  amount  and  concentration  of  the  substance  and  thus  on  the  pollution  risk,  certainly  in 
groundwater. 

6.2.  Integrating the economic dimensions of water use and management 

As indicated above, physical water balances can be linked to socio-economic information on 
the different economic activities that affect directly or indirectly the quantitative state of water 
resources.  For  example,  economic  information  on  the  main  water  abstractors  such  as  gross 
income, value added or employment collected as part of the WFD Article 5 assessment can be 
compared to the water abstraction/pressure imposed by each sector so an average productivity 
of water is estimated. This can provide an overall picture of the economic importance of water 
quantity for a water catchment or river basin. Methodologies to address cost-recovery issues 
in the context of Article 9, in particular the assessment and recovery of resource costs, could 
also be developed building on the establishment of water balances [21].  

This  integration  can  then  support  the  identification  of  potential  measures  that  might  help 
address  gaps  in  water  status  while  accounting  for  the  economic  importance  of  water 
abstractors,  including  for  assessing  whether  exemptions  in  the  achievement  of  the  WFD 
objectives might be considered and justified.  

37 Experimental Water quality accounts are considered under the SEEA Water framework. They describe the quality of the stocks of water 
resources, and have a simpler structure than the assets accounts, as changes in quality are the result of non-linear relationships. It is 
however not possible to distinguish changes in quality due to human activities from changes in quality due to natural causes. One of the 
main  problems  in  their  application  is  the  little  standardization  at  the  international  level  of  concepts  and  definitions  or  aggregation 
methods for the definition and the measurement of water quality classes. [10] 

38 Clearly, as average nutrient loads and river flows for the water balance chosen time scale (usually the year or the month) are considered, 

this does not take account of the significant variability that might exist within the chosen time scales. 

45 

 
                                                 
Additional  efforts  can  be  made  to  make  the  water-economic  relationships  more  explicit  by 
including  water  use  per  sector,  water  reuse  or  the  importance  of  water  desalination.  Such 
information  may  be  useful  when  considering  options  in  cases  where  insufficient  water  is 
available to satisfy both the desired potential societal water use and the desired allocation of 
water to the environment. 

Purely  economic  information  on  the  main  users  (e.g.  agricultural  yields,  income  generated, 
etc.)  can  also  be  specified,  linking  production  values  to  availability  and  water  use,  and 
providing  the  possibility  to  illustrate  the  effectiveness  of  policies  aimed  at  a  decoupling  of 
economic  growth  and  water  use  or  (including  emissions  to  water  (see  Box  14).  By  adding 
information on conveyance efficiency, water losses and water demand for the main users, the 
water balance leads to an overall water census that can support the:  

Identification  of  the  potential  for  water  conservation  and  improvements  in  water 

efficiency; 

The  identification  of  water  stress  (as  a  temporal  mismatch  between  availability  and 

demand); 

The evaluation of the  water supply reliability; 

  The understanding of the impact (estimated) future water demand might have on the 
sustainability  of  water  resources  in  a  climate  change  context  –information  that  is 
necessary for proactive water (but also land-use) planning. 

Complemented with  information  on the unitary costs of potential measures  (Investment  and 
Operation and Maintenance Costs in € per ha or per water saving device), and expected water 
savings or additional water supply that would be expected from the implementation of these 
measures.  For  instance,  water  balances  can  support  cost-effectiveness  analysis  and  the 
prioritisation  of  measures  when  preparing  the  WFD  RBMP  and  Programmes  of  Measures 
(PoM).  In  such  assessments,  effectiveness  can  be  considered  as  (1)  the  contribution  of 
individual measures to a given river discharge target/objective (e.g. in % of improvement as 
compared to the current discharge level, or in contribution to river discharge in m3/s), (2) the 
restoration  of  a  given  groundwater  level  or  (3)  the  contribution  to  balancing  net  aquifer 
recharge.  

Cost-effectiveness  ratios  estimated  for  each  individual  (demand  or  supply)  measure  help 
ranking  and  prioritising  measures  because  of  their  favourable  cost-effectiveness  ratio, 
including, whenever relevant, Natural Water Retention Measures (NWRM) [20].   

When information on the marginal value of water (i.e. the expected unitary income loss that 
would result from the removal of, or addition of one cubic meter to, a given water abstractor) 
is  available 39,  the  marginal  values  of  water  for  different  water  uses  can  be  compared.  
Marginal  values  of  water  can  provide  useful  information  for  management  of  abstraction 
permits/consents. It might also help in revising current water abstraction permits/consents, or 
support  the  development  of  flexible  mechanisms  that  allow  for  water  reallocation  between 
individual holders of water permits/consents that might support socio-economic development 
at no additional pressure on water resources.  

39

Usually obtained from econometric models or from simulation using available hydro-economic models.

46 

 
 
Box 17. NAMWA: Linking water accounts to economic data  
Over the past decades, the demand for information about the economic value of water and the wider economic consequences 
of water policy and management has increased rapidly. Obviously, the introduction of the WFD has given this demand an 
important  impulse.  To  meet  this  growing  demand,  the  Dutch  Ministry  of  Environment  and  Infrastructure  and  Statistics 
Netherlands  have  developed  an  integrated  water  economics  information  system  called  the  National  Accounting  Matrix 
including  Water  Accounts  (NAMWA).  Following  a  pilot  project  in  1997  (De  Haan,  1997),  the  Dutch  system  of 
environmental  accounts  (NAMEA)  was  extended  in  2002  with  the  water  accounts.  NAMWA  is  a  further  specification  of 
NAMEA for water, using the same accounting structure (Van der Veeren et al., 2004; Brouwer et al., 2005). The Dutch water 
accounts  present  information  at  the  level  of  the  four  main  river  basin  districts  in  the  Netherlands:  Meuse,  Scheldt,  Ems, 
Rhine-North, Rhine-West, Rhine-East and Rhine-Centre. The information of those water accounts  are used as input for the 
Dutch economic analyses reports for the WFD.  

The  NAMWA-matrix  consists  of  10  monetary  accounts  and  4  physical  accounts.  The  first  two  physical  accounts  for  the 
emission  of  substances  and  water  extraction  and  discharge  represent  the  flows.  The  third  physical  account  for  water 
extraction  and  discharge  describes  changes  in  stocks,  while  the  fourth  physical  account  for  emissions  describes  the 
contribution  of  various  substances  to  ‘environmental  themes’  such  as  eutrophication  or  the  dispersion  of  heavy  metals  in 
water. By linking water and substance flows to economic flows and doing this systematically for a number of years, insight is 
gained into the (nature of the) relationship between our physical water systems and the economy. The integration of physical 
and economic information also allows the construction of integrated indicators. For instance, water use by various economic 
sectors can be related to the economic interests involved. By linking information about the physical pressures exerted on the 
water  system  by  economic  agents  and  the  associated  economic  interests,  NAMWA  enables  policy  makers  and  water 
managers at national and river basin scale in a consistent way to assess the necessary measures to reduce these pressures and 
meet the environmental objectives in the WFD in an integrated way. NAMWA offers opportunities to analyse the trade-offs 
between environmental goals and the economic interests involved at the relevant level of analysis, i.e. river basins. 

For  more  details,  see  http://www.helpdeskwater.nl/publish/pages/5396/anewintegratedriverbasininformationsystem.pdf    & 
Brouwer,  R.  Schenau  S.J.  and  van  der  Veeren,  R.  (2005),  Integrated  river  basin  accounting  in  the  Netherlands  and  the 
European Water Framework Directive. UNECE Statistical Journal ECE 22, 111–131. 

47 

 
 
 
 
Box 18. Water productivity based upon SEEA water account tables 

The SEEA-W methodology allows the management of information from standardised official databases, organising data in 
standard tables and using these to produce indicators that can serve for temporal or spatial comparisons.  The tables for the 
Guadalquivir basin (2004-2012) have been used to follow the impact of meteorological droughts (years 2005 and 2012) and a 
hydrological drought (2005-2008). This was done by following the evolution of the ratio 'Gross Added Value (GAV)/water 
consumed', discriminating the role of irrigation water (blue) and soil water (green) according to SEEA-W definitions.  

(*) GAV constant prices 2012; GW= soil (green) water; BW=irrigation (Blue) water 

Green (soil) water in irrigated land accounts for  about 62% of water consumed by  crops (increasing up to 70% during the 
hydrological  drought  from  2006  to  2008  when  irrigation  restrictions  are  applied).  The  ratio  'GAV/water  consumed'  shows 
that  water  apparent  productivity  for  rain  fed  agriculture  is  0.09  EUR/m3  compared  with  0.48  EUR/m3  for  irrigated  land. 
When the denominator of irrigated land excludes soil water and includes only irrigation supply, the apparent productivity of 
irrigation  water  increases  to  1.33  EUR/m3.  This  type  of  information  can  help  water  managers  understand  the  economic 
consequences  of  different  options  when  allocating  water  to  different  uses  and  may  support  the  evaluation  of  measures  to 
prevent  impact  of  climatic  events  (see  Borrego-Marín,  M.M.,  J.M.  Perales,  A.  Posadillo,  C.  Gutiérrez-Martín  y  J.  Berbel 
(2015  Analysis  of  Guadalquivir  droughts  2004-2012  based  on  SEEA-W  tables.  International  Conference  Drought  R&SPI 
2015. Valencia). 

48 

 2004 2005 2006 2007 2008 2009 2010 2011 2012 Average GAV (Million EUR*)           Livestock+Forest 616 484 459 573 598 600 650 688 630 589 Rain-fed 1.112 874 830 1.035 1.081 1.083 1.174 1.243 1.138 1.063 Irrigation 3.045 2.393 2.272 2.834 2.959 2.967 3.214 3.403 3.117 2.912 Water (mm)           Forest Soil Water 495 277 460 488 458 448 504 491 336 440 Rainfed Soil (GW) 511 270 469 490 464 464 509 507 325 446 Irrigated land Soil Water 537 252 470 496 471 476 537 537 304 453 Irrigation (BW) 343 389 198 190 194 276 284 279 345 278 VAB/Water (EUR/m3)           Total Consumed Water 0,15 0,20 0,13 0,15 0,17 0,16 0,16 0,17 0,23 0,17 Forest + LIvestockSoil GW 0,06 0,08 0,05 0,06 0,06 0,06 0,06 0,07 0,09 0,06 Total Irrigation (GW+BW) 0,48 0,45 0,41 0,49 0,53 0,46 0,46 0,48 0,55 0,48 Rainfed Soil GW 0,08 0,12 0,06 0,08 0,09 0,09 0,08 0,09 0,13 0,09 Irrigation (BW) 1,24 0,74 1,37 1,78 1,80 1,26 1,32 1,42 1,04 1,33 Irrigation residual BW 1,12 0,66 1,22 1,58 1,59 1,11 1,16 1,24 0,93 1,12 % Soil water IRR 61% 39% 70% 72% 71% 63% 65% 66% 47% 62% % Blue Water IRR 39% 61% 30% 28% 29% 37% 35% 34% 53% 38%   
 
 
Box 19. Estimating technical and economic indicators in the WAMCD project (see Annex II for more information) 

In the SEEAW Guidance Document, four types of indicators are proposed to synthesize the massive amount of information 
compiled, each representing a potential aspect of water management and /or RBM planning under the IWRM approach. The 
WAMCD  project  team  has  selected  a  collection  of  relevant  technical  and  economic  indicators  that  can  be  obtained  from 
SEEAW  tables  or  auxiliary  datasets  and  may  facilitate  handling  information  and  extracting  helpful  conclusions.  These 
indicators were calculated for three different scenarios: 2009 baseline, corresponding to RBMP-09, 2015 current scenario 
of RBMP-15 and 2021 future scenario after the first stage of implementation of the PoM.  

Box 20. Financial cost recovery estimation based upon SEEA 

The  Guadalquivir River is the longest river in southern Spain with a length of around 650 km. Its basin covers an area of 
57,527 km2 and has a population of 4,107,598 inhabitants. Agriculture is the main user in the basin and it has implemented 
an  intense  investment  in  water  saving  measures.  The  philosophy  of  SEEA  Water  is  based  on  time  and  resource  saving 
efficiency in data gathering. It is crucial that data are based on officially published information avoiding 'ad hoc' estimations. 
Following  this  strategy,  project  SYWAG  has  estimated  cost  recovery  rates  in  the  SEEA  Water  tables.  SEEA  includes 
information for a) the capital and investment costs b) operational and maintenance costs of  water  services, c)  Government 
account table for water-related collective consumption services d) Financing accounts. By combining information included in 
those tables, SYWAG obtained the following result 

(*)  Non  recovered  cost  for  water  irrigation  distribution  are  justified  by  the  reduction  in  farmers’  water  rights  (25%  on 
average). 

A  detailed  study  of  material  and  methods  can  be  seen  at  Berbel,  J.,  Borrego-Marín,  M.M.  y  Gutiérrez-Martín,  C.  (2015). 
System  of  Water  Accounting  in  Guadalquivir  River  Basin  (SYWAG).Final  Report.  Universidad  de  Córdoba.  Colección: 
DESPA.  http://hdl.handle.net/10396/12557.  

49 

  Financial cost recovery index Service cost recovery (Estimation for 2012) Urban  Agrarian Industry Total  1 2 3   Water supply: abstraction, storage and distribution, surface and groundwater  Upper level surface services 74% 64% 76% 66% Collective groundwater abstraction 100%     100% Water irrigation distribution   73%(*)   73% Urban cycle (distribution of drinking water)  97%     97% Self service (surface & GW)   100% 100% 100% Reuse   100%   100% Collection and treatment of sewage water Non connected collection  --  --  100% 100% Public network collection 93%     93%   87% 75% 91% 78%   2009 2015 2021 Units A) Water resource availability A1. Renewable resources 1,660.49 1,681.05 1,692.40 hm3/year A2. Per capita renewable resources 636.26 607.14 590.95 m3/resident.year A3: Consumption index 56.70% 56.63% 57.18% dimensionless A4: Exploitation Index 114.59% 113.97% 113.94% dimensionless A5: Use of renewable vs. non-renewable water resources 34.48% 34.04% 19.60% dimensionless B) Water use for human activities B1-a: Water use per unit produced. ISIC I-3 1.24 1.30 1.28 m3/€ B1-b: Water use per unit produced. Rest of human activity 0.04 0.04 0.04 m3/€ B2-a: Water Productivity Ratio. ISIC I-3 0.81 0.77 0.78 €/m3 B2-b: Water Productivity Ratio. Rest of human activity 26.69 26.48 26.13 €/m3 B3: Water pollution per person (only ISIC 37) n.a. 53.371 54.692 Kg COD/resident.year B5: Decontamination ratio (only ISIC 37) n.a. 79.73% 83.76% dimensionless   
 
 
 
 
 
 
 
 
 
 
 
 
Box 21. Cost effectiveness analysis (CEA) applied to water-saving measures in the Guadalquivir basin 

Average renewable resources in the Guadalquivir River Basin (GRB) amount to 7,230 Mm3/year, from which in an average 
year 3,850 Mm3 are used. Per capita water consumption in the GRB is 950 m3. Currently, the main water uses in the basin 
are agriculture (85%), domestic use (11%), industrial use (3%) and tourism. Cost effectiveness analysis (CEA) was applied to 
water-saving measures. CEA is a form of economic analysis that compares the costs and outcomes (effects) of two or more 
courses of action. Generally in water management, the objective of CEA is to bridge the gap between the total water supply 
and total projected consumption. In the context of the WFD, the objective is to achieve good status, and therefore the goal of 
the  Programme  of  Measures  (PoM)  is  to  reach  a  sustainable  rate  of  water  consumption  while  maintaining  minimum 
environmental stream flows and groundwater levels.  

The  term  ‘measure’  is  understood  here  as  a  specific  intervention,  which  can  include  management  programmes  and/or 
techniques,  aimed  at  saving  water.  Here  the  focus  is  on  the  measures  discussed  in  the  public  participation  process  for  the 
elaboration of the PoM for the Guadalquivir River Basin. An additional complexity in the case study of the Guadalquivir for 
water  saving  measures  is  that  some  of  the  defined  “measures”  by  the  PoM  imply  a  combination  of  both  technical  and 
economic instruments. An example maybe the complex measure called ‘irrigation modernization” which is the improvement 
of irrigation networks that generally includes the substitution of open channel irrigation by pressurized systems, introduction 
of  metering  devices  and  volumetric  billing  leading  to  price  increase.  The  next  step  in  the  model  is  the  estimation  of  the 
effectiveness and the costs of the measures to calculate the CE ratio. The challenges here are: i) information availability;  ii) 
avoiding double counting over the different measures; and iii) accurately measuring the impact of the measure. 

Water-saving measures 

in 

in 

of 

urban 

Improvement 
distribution networks 
Modernisation  of  irrigation 
systems 
Service  cost  recovery 
urban sector 
Service  cost  recovery 
irrigation 
Volumetric 
irrigation 
Extension 
irrigators 
Subtotal 
Strict 
abstraction control 
Total 

groundwater 

services 

billing 

for 

for 

Effectiveness 

Pressure 
reduction 
(Mm3) 

Impact 
reduction 
(Mm3/year)  

Annual 
Equivalent 
Cost (106€ 
per year ) 

44.99 

2.19 

21.61 

259.51 

35.26 

172.18 

17.59 

22.46 

38.26 

9.78 

392.59 

323.11 

715.71 

9.58 

2.20 

5.90 

1.58 

56.72 

80.38 

18.55 

2.41 

6.20 

3.82 

224.77 

5.50 

137.09 

230.27 

CE pressure 
reduction 
(€/m3) 

CE impact 
reduction 
(€/m3) 

0.48 

0.66 

1.05 

0.11 

0.16 

0.39 

0.57 

0.02 

0.32 

9.87 

4.88 

1.94 

1.10 

1.05 

2.42 

3.96 

0.07 

1.68 

Source: Berbel, J., Martin-Ortega, J., & Mesa, P. (2011). A cost-effectiveness analysis of water-saving measures for the water 
framework directive: the case of the Guadalquivir River Basin in Southern Spain. Water Resources Management, 25(2), 623-
640. DOI.10.1007/s11269-010-9717-6 

The analysis of cost and effectiveness of measures is made at water mass level, and there are around 400 water masses in the 
Guadalquivir  River  Basin.  The  measures'  impact  analysis  is  made  by  aggregating  them  accordingly  to  account  for  spatial 
interactions  between  the  different  water  bodies  in  the  river  basin,  as  some  water-saving  measures  upstream  will  positively 
affect water bodies downstream. Because of the spatial interactions, the cost of reducing the pressure on a downstream water 
body will be significantly lower  if  water-saving  measures are undertaken upstream.  There are differences between CEA in 
the 'pressure reduction' ratio (defined as reduced water 
abstraction)  and  CEA  defined  as  'impact  reduction' 
ratio when return flows are taken into account and real 
impact 
is 
considered. 

in  water  masses  quantitative  status 

The Figure in this example illustrates data contained in 
the table, (central continuous line) defined as the 'most 
probable  cost  and  effectiveness.  Discontinuous  line 
above and below the 'most probable' show the 'pessimistic' and 'optimistic' estimation of cost and effectiveness. This allows 
the integration of a measure of uncertainty assumed as a triangular distribution (pessimistic, most-likely, optimistic). 

50 

 
 
 
 
 
 
 
6.3.  EEA and Eurostat related works 

Estimation  of  Water  Assets  Accounts  for  Europe  is  the  first  step  of  this  analysis  towards 
obtaining  information  on  the  Water  Exploitation  Index  (WEI).  Based  on  the  previous  EEA 
experiences on Water Accounts and WEI three spatial scales (i.e. Sub basin, River Basin and 
Country) and three temporal resolutions (monthly, seasonal and annual) have been chosen to 
present  the  results.  The  UN  SEEA–Water  framework  is  the  conceptual  framework  for  the 
asset accounts. Therefore, the results of assets accounts introduced in the EEA's study are in 
line with standard water availability and the water use tables of that framework also provides 
information on water use by the economic sectors in the respective area and time period. The 
parameters are also in line with the Eurostat collection on water statistics.  

The  WEI+  results  are  calculated  as  derived  results  from  the  water  balances  arising  from 
the   European Water Assets Accounts. Water Exploitation Index (WEI+) is understood as an 
indicator  for  presenting  water  scarcity  conditions  across  Europe.  Formulas  were  developed 
and agreed by the “Expert network on water scarcity and droughts” and the “Working group 
on water accounts” under the CIS for the WFD. Two different formulas were endorsed by the 
Water  Directors  in  implementing  the  Renewable  Water  Resources.  The  EEA  presents  the 
results  from  both  formulas.   Following  this,  the  WEI  also  describes  sectorial  pressures  over 
the renewable water  resources.   The tool (the EEA WA-infrastructure) is  flexible enough to 
accommodate possible further adjustments of the formula.  

The EEA Water Accounts infrastructure is not only producing results from Water Accounts, 
but  also  provides  data  and  information  to  further  assess  water  quality  in  different  domains 
(such as the JRC work on water consumption and efficiency in the service sector). 

The results suggest the following interpretation of the water resource situation across Europe 
(as  the  data  sources  and  the  details  of  the  methodology  are,  at  the  time  of  writing,  under 
consultation, these should be considered as preliminary): 

  Assessment  of WEI  at  sub basin  scale on monthly/seasonal  resolutions  revealed that 
the freshwater systems are under pressure especially in Mediterranean countries due to 
high irrigation water demand in summer months, while the rest of Europe experiences 
lower water scarcity stress by other economic sectors as water collection treatment and 
supply, energy and industries.  

  From  the  environmental  perspective,  high  water  demands  overlap  in  lower  available 
renewable  water  resources  particularly  in  summer  months,  which  create  partly 
additional stress over the freshwater resources.  

  As water availability is a site-specific phenomenon, spatial aggregation of water stress 
and scarcity for instance to the country scale is prone to hide the real conditions in the 
respective less  aggregated areas.  In this sense, the study also verifies the  findings in 
the previous studies on regionalised WEI. Sectorial share of water abstraction and use 
is  crucial  information  for  the  policy  makers  and  stakeholders  in  assessing  water 
resources efficiency and implementing the measures to tackle environmental concerns 
including the role of water resources as part of total natural capital. 

Regarding  Eurostat,  the  entity  is  organising  collections  of  data  from  the  members  of  the 
European  Statistical  System  (ESS:  EU+EFTA  countries)  by  means  of  the  OECD/Eurostat 

51 

 
 
Joint  Questionnaire  on  Inland  Waters  (JQ-IW,  national  level)  and  the  Eurostat  Regional 
Environmental  Questionnaire  (REQ,  for  NUTS2  and  RBD/SU  aggregations).  Both  data 
collections include a table addressing water resources; these tables could be at least partially 
(pre-)filled  with  data  from  water  balances  exercises  and  pilot  projects.  Total  water 
abstractions and returns are likewise elements of other central tables in the JQ-IW and REQ, 
so  that  these  data  can  be  complemented  and  counterchecked  with  statistical  information 
available  from  the  ESS.  Complete  recording  of  metadata  including  estimates  of  accuracy 
would vastly enhance the value and usability of the water balance data sets. 

52 

 
 
7.  RECOMMENDATIONS AND CONCLUSIONS 

To  support  the  implementation  of  the  WFD,  due  consideration  needs  to  be  given  to  water 
quantity issues to better understand the balance between water supply and water demand and 
the current balance or imbalance of water resources, as a pre-condition for achieving the WFD 
environmental  objectives  (in  particular:  Good  Ecological  Status  for  Surface  Water  bodies, 
Good  Quantitative  Status  for  Groundwater  bodies,  no  deterioration  for  both  water  body 
types). As summarised in the following table, water balances are tools that can help support 
the  sound  implementation  of  the  WFD  so  its  environmental  objectives  are  achieved  in  a 
cost-effective manner40.  

Table  3.  Potential  applications  of  water  balances  for  supporting  the  implementation  of  the 
WFD 

WFD 
implementation 
step 
Characterisation 
of river basins 
(Article 5) 

Development of 
the RBMP and 
PoM (Article 11, 
Annex III & 
Annex VII) 

Role of water balances 

Possible expansion of water balances 

Identification of areas with imbalance 
between water supply and water demand 
(today and under baseline scenario 
conditions) 
Identification of significant “quantitative” 
pressures on water status (significant water 
abstractors, pressures on water infiltrations, 
etc.) 

Assessment of the effectiveness of 
individual measures (including adaptation in 
current water abstraction permits/consents) 
and selection of measures required for 
achieving good status (ecological flow, 
groundwater quantitative status, no 
deterioration) 
Climate proofing of measures 

Integration of socio-economic data 
(economic importance of water uses) to 
capture the role of water resources in the 
socio-economic development of river 
basins and for performing the assessment 
of cost-recovery (Article 9) 
Integration of water quality data to 
strengthen against the risk of failure to 
achieve good chemical status 
Assessment of costs of measures to 
perform cost-effectiveness analysis and 
prioritizing measures 
Integration of socio-economic information 
on the economic value of water to perform 
the assessments required if exemptions are 
considered  

Water balances are tools that can help MS to carry out their assessment of the potential risk 
of quantitative imbalance, be it today or in the future if no preventive action is taken. They 
can  be  developed  and  applied  when  carrying  out  the  WFD  Article  5  analysis,  helping  to 
identify:  (1)  water  bodies  and/or  catchments  that  are  at  quantitative  risk  and  for  which 
measures  should  be  proposed  for  closing  the  water  status  gap;  (2)  significant  pressures  that 
explain  current  water  imbalances;  and  (3)  possible  gaps  in,  and  incoherence  between,  the 
existing  knowledge  base  on  the  different  components  of  the  hydrological  cycle  and  on  the 
inventory of water abstractions.  

Water balances should be built in a stepwise and tiered approach, with a preliminary analysis 
of current management challenges helping to define the key components of the water balance 
that require specific attention. In addition, managers should identify time and spatial scales at 
which  it  is  relevant  to  develop  the  water  balance  so  it  can  help  supporting  management 

40 Developed with the right level of detail accounting for available data, available human/financial resources and the expected  value added, 

water balances might deliver in supporting water management. 

53 

 
 
                                                 
discussions  and  decisions.  Water  balances  should  explicitly  consider  the  environmental 
demand of aquatic ecosystems in coherence with the definition of Eflows for surface waters.  

Water balances can also be used to select measures for the WFD PoM. They can help: (1) 
assess  the  effectiveness  of  measures  proposed  for  improving  the  quantitative  balance  of 
surface and groundwater resources; (2) review  existing  water abstraction  permits; (3) assess 
the relevance of water efficiency measures or development of water reuse. 

Complemented with  information  on the costs of  measures, they  can help  prioritise potential 
measures based on their cost-effectiveness ratio and identify the combination of measures that 
can achieve a sustainable use of water resources at the lowest possible cost. In some cases, the 
technical, environmental and economic information provided, when linking water balances to 
socio-economic information, can help investigate the need for any WFD exemptions. Finally, 
water  balances  are  critical  to  enable  the  comparison  of  the  different  management  options 
including the development of new infrastructure (e.g. dams) that require an exemption under 
Article 4(7) of the WFD. 

Accounting for future climate change scenarios and their impacts on rainfall, water balances 
can  also  provide  useful  information  for  climate-proofing  of  measures,  and  for  selecting 
measures that enhance the resilience of aquatic ecosystems.  In addition, they can be used as 
the basis for emergency plans in case of water shortages and of conflicting water uses.  

Water balances are one of several approaches that can shed light on the issues linked to the 
sustainability  of  water  management,  water  availability  and  (efficient)  water  resource 
use.  Other  approaches  that  have  clear  connections  to  the  components  and  applications  of 
water balances include, for example, life-cycle analysis or analysis of water footprints.  

It  is  important  that  further  efforts  are  made  for  these  approaches  to  be  applied  more 
systematically  in  the  context  of  environmental,  water  resource  and  resource  efficiency 
strategies  while  accounting  for  future  socio-economic  development  and  climate  change.  In 
addition  to  supporting  the  implementation  of  the  WFD,  this  will  contribute  to  the 
identification  of  measures  and  solutions  that  best  support  the  sustainable  development  of 
Europe.  

54 

 
 
8.  LIST OF REFERENCES 

References in the main text: 

[1]  Kossida  M.,  Kakava,  A.,  Tekidou,  A.,  Iglesias  A.,  Mimikou,  M.  2012.  Vulnerability  to 
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[2] Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 
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[3]  Communication  from  the  Commission  to  the  European  Parliament,  the  Council,  the 
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scarcity and droughts in the European Union (COM (2007) 414 final. 

[4]  Communication  from  the  commission  to  the  European  parliament,  the  Council,  the 
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[6]  Commission  of  the  European  Communities  White  Paper  Adapting  to  climate  change: 
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[8]  UNSD  (2012).  [9]  UNESCO-IHP  (1990).  Guidelines  for  water  resource  assessment  of 
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[9]  EEA  (2015  draft  document).  European  Water  Assets  Accounts  and  updating  the  use  of 
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[10]  UN  (2012).  System  of  Environmental  Economic  Accounting  for  Water.  Department  of 
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[11]  Ad  de  Roo,  Peter  Burek,  Alessandro  Gentile,  Angel  Udias,  FaycalBouraoui,  Alberto 
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IneVandecasteele, Sarah Mubareka, Claudia Baranzelli, Marcel Van Der Perk, Carlo Lavalle, 
Giovanni  Bidoglio.  (2012).  A  multi-criteria  optimisation  of  scenarios  for  the  protection  of 
water  resources  in  Europe:  Support  to  the  EU  Blueprint  to  Safeguard  Europe’s  Waters. 
European  Commission  Joint  Research  Centre,  Institute  for  Environment  and  Sustainability. 
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[12] Kossida, M., Lourmas, G., Avramidi, E., Bouziotas, D., Fringis, I., Ribarova, I., Tsanov, 
E., Ninov, P., Dimova, G., Grigorov, G., Moramarco, T., Barbetta, S., Brocca, L., Maccioni, 
P.,  Volk,  M.,  Koch,  F.,  Weiner,  J.,  Ledermüller  S.,  Makropoulos,  C.,  Sotiropoulos,  E., 
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55 

 
ABOT  project  Deliverable  D.C2.  ABOT  “Assessment  of  water  Balances  and  Optimisation 
based  Target  setting  across  EU  River  Basins”,  Preparatory  Action  on  development  of 
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[13]  Henriksen 
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and  Refsgaard 

groundwater 

Sustainable 

(2013) 

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[15] Raudkivi, A.J. (1979). Hydrology: An Advanced Introduction to Hydrological Processes 
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[16] Faergemann, H. (2012). Update on Water Scarcity and Droughts indicator development, 
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[17] Kossida, M., Mimikou M. (2013). Internal Report on the Water Accounts work and the 
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[18]  Smakhtin,  V.,  Revanga,  C.,  Doll,  P.  (2005).Taking  into  Account  Environmental  Water 
Requirements  in  Globalscale  Water  Resources  Assessments.  IWMI  The  Global  Podium, 
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[19]  European  Commission  (2015).  EU  Reference  document  Good  Practices  on  Leakage 
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[20]  European  Commission  (2014).  EU  policy  document  on  Natural  Water  Retention 
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(WG 
c40324d22ad3/Policy%20Document%20on%20Natural%20Water%20Retention%20Measure
s_Final.pdf  

PoM). 

Additional relevant references: 

Alley,  W.M.,  Evenson,  E.J.,  Barber,  N.L.,  Bruce,  B.W.,  Dennehy,  K.F.,  Freeman,  M.C., 
Freeman,  W.O.,  Fischer,  J.M.,  Hughes,  W.B.,  Kennen,  J.G.,  Kiang,  J.E.,  Maloney, 
K.O., Musgrove, MaryLynn, Ralston, Barbara, Tessler, Steven, and Verdin, J.P. (2013). 
Progress  toward  establishing  a  national  assessment  of  water  availability  and  use.U.S. 
Geological Survey Circular 1384, 34 p. 

Asheesh,  M.  (2003).Allocating  the  Gaps  of  Shared  Water  Resources  (The  Scarcity  Index) 

Case Study Palestine Israel." IGME, 2003: 797-805. 

Defra.  2011.  Water  white  paper  -  Water  for  Life  HM  Government,  December  2011,  ISBN: 

9780101823029. 

Delsalle,  J.  (2013).  Discussion  document  on  EU  water  balances  at  sub-catchment  level, 

presented to the SCG Meeting, 22 March 2013, Brussels. 

56 

 
 
EC (2000).Directive 2000/60/EC of the European Parliament and of the Council establishing 
a framework for Community action in the field of water policy.OJ L327, 22.12.2000.  

EC  (2007).Communication  from  the  Commission  to  the  Council  and  the  European 
Parliament,  Addressing  the  challenge  of  water  scarcity  and  droughts  in  the  European 
Union. Brussels, 18.07.07, COM(2007)414 final.  

EC (2011a). Communication from the Commission to the European Parliament, the Council, 

the European Economic and Social Committee and the Committee of the Regions, A 
resource-efficient Europe - Flagship initiative under the Europe 2020 Strategy. Brussels, 
26.01.2011, COM(2011)21 final.  

EC (2011b).Communication from the Commission to the European Parliament, the Council, 
the  European  Economic  and  Social  Committee  and  the  Committee  of  the  Regions, 
Roadmap to a Resource Efficient Europe. Brussels, 20.09.2011, COM(2011)571 final. 

EC (2012a).Communication from the Commission to the European Parliament, the Council, 
the  European  Economic  and  Social  Committee  and  the  Committee  of  the  Regions. 
Report  on  the  Review  of  the  European  Water  Scarcity  and  Droughts  Policy 
{SWD(2012) 380 final}. COM(2012) 672 final, Brussels, 14.11.2012. 

EC (2012b).Communication from the Commission to the European Parliament, the Council, 
the  European  Economic  and  Social  Committee  and  the  Committee  of  the  Regions.A 
Blueprint  to  Safeguard  Europe's  Water  Resources.COM(2012)  673  final,  Brussels, 
14.11.2012. 

EEA (2011).Resource efficiency in Europe, Policies and approaches in 31 EEA member and 

cooperating countries, EEA Report, No 5/2011  

EEA  (2012a).Towards  efficient  use  of  water  resources  in  Europe,  EEA  Report,  No  1/2012, 

European Environment Agency. 

EEA (2012b).Water Accounts: summary of the results so far, 26/10/2012, Note presented to 

the SCG Meeting, 07-08 November 2012, Brussels. 

EEA  (2012c).Water  resources  in  Europe  in  the  context  of  vulnerability,  EEA  Report  No 

11/2012, European Environment Agency. 

EEA (2013). Results and lessons from implementing the Water Assets Accounts in the EEA 

area. EEA Technical Report No 7/2013, May 22, 2013, Copenhagen. 

Environment  Agency.  2012.  ‘Improving 

the  classification  of  water  stressed  areas: 

Consultation document’.  Environment Agency, Bristol, UK, November 2012. 

Garrote,  L.,  Martin-Carrasco,  F.,  Flores-Montoya,  F.,  Iglesias,  A.  (2007).  Linking  Drought 
Indicators  to  Policy  Actions  in  the  Tagus  Basin  Drought  Management  Plan.  Water 
Resources Management, May 2007, Volume 21, Issue 5, pp 873-882) 

Healy,  R.W.,  Winter,  T.C.,  LaBaugh,  J.W.,  and  Franke,  O.L.  (2007).  Water  budgets: 
Foundations  for  effective  water-resources  and  environmental  management.  U.S. 
Geological Survey Circular 1308, 90 p. 

Hellenic Ministry of Environment, Energy and Climate Change and NAMA S.A., 2012.River 
Basin  Management  Plan  of  the  River  Basin  District  of  Eastern  StereaEllada  (GR07). 
Phase  B,  Deliverable  4,  Drought  and  Water  Scarcity  Management  Plan  (in  Greek). 
Special  Secretariat  for  Water,  Hellenic  Ministry  of  Environment,  Energy  and  Climate 
Change. 

57 

 
Kossida  M.,  Koutiva  I.,  Makropoulos  C.,  Monokrousou  K.,  Mimikou  M.,  Fons-Esteve  J., 
Iglesias  A.  (2009).  Water  Scarcity  and  Drought:  towards  a  European  Water  Scarcity 
and  Drought  Network  (WSDN).  ETC/ICM  Report  for  the  European  Environment 
Agency EEA, released 13/07/2009. 

Kossida,  M.  (2009).  WISE-SoE  WQ  Data  Request-Data  Input  Tool  for  the  WISE-SoE#3 
“State  and  Quantity  of  Water  Resources”  User  Manual.  Publication  for  the  EEA, 
Copenhagen. 

Lane, M., Kirshen, P. H., Vogel, R. (1999).Indicators of impacts of global climate change on 
U.S.  water  resources.  Journal  of  Water  Resources  Planning  and  Management,  125(4), 
194–204. 

Ribarova,  I.,  Tsanov,  E.,  Ninov,  P.,  Dimova,  G.,  Grigorov,  G.,  Kossida,  M.,  Lourmas,  G., 
Moramarco, T., Barbetta, S., Brocca, L., Maccioni, P., Volk, M., Koch, F., Weiner, J., 
Ledermüller S., Makropoulos, C., (2012). Policy Brief on the water balances in the pilot 
RBs.  ABOT  project  Deliverable  D.C1.1.  ABOT  “Assessment  of  water  Balances  and 
Optimisation  based  Target  setting  across  EU  River  Basins”,  Preparatory  Action  on 
development  of  prevention  activities  to  halt  desertification  in  Europe  Halting 
desertification in Europe – 2011, DG ENV. 

Schenau,  S.  and  Ten  Ham.M.  (2005).Water  Accounts  and  the  Water  Framework  Directive. 
Statistics  Netherlands  (CBS),  Department  of  National  Accounts,  Voorburg,  The 
Netherlands. 

Schmidt, G. and Benítez, C. (2012).Topic Report on Water Scarcity and Droughts Aspects in 
a selection of European Union River Basin Management Plans, Topic Report, Version 
3.0.Service  contract  for  the  support  to  the  follow-up  of  the  Communication  on  Water 
Scarcity and Droughts. European Commission, Intecsa-Inarsa S.A. and Typsa. 

United Nations Statistics Division (2007).System of Environmental-Economic Accounting for 

Water. Final Draft, March 2007.   

58 

 
 
 
 
 
 
ANNEXES 

ANNEX I – ILLUSTRATING THE APPLICATION OF WATER BALANCES 

Case study #1: Ali-Efenti River Basin, Greece (ABOT project, DG ENV) 

The Ali-Efenti River Basin is located in the North-western part of the Pinios River 
in Thessaly RBD (GR08), in Greece.  Two main urban centres (the cities of Trikala 
and  Karditsa)  are  within  the  basin,  while  numerous  significant  peri-urban 
settlements are also present (Kalambaka, Mouzaki, Neoxori, etc.), all together with 
a total permanent population of 190,276 inhabitants.  

In  terms  of  land  use  the  area  is  dominated  by  agriculture  and  forests  (about  33% 
each),  followed  by  pasture  (30%)  and  urban  (2%).  The  long-term  annual  average 
precipitation  in  the  basin  has  a  high  spatial  variability,  ranging  from  1,000-1,300 
mm in the west, to a lower precipitation of 460-600 mm in the east. 

Study Area: 
Ali-Efenti River 
Basin, Greece 

Which are the main 
challenges with 
regard to water 
management in the 
study area? 

How did the 
development of 
Water Balances 
support local water 
management and 
help alleviate the 
problem? 

This basin has extended irrigation areas (the main crop cultivated is cotton), while 
irrigation  efficiency  is  low.  Imbalance  between  demand  and  availability  (water 
stress) is frequent, and the unmet demand is highly pronounced during the summer 
period.  As  a  result  over-abstraction  has  led  to  environmental  impacts,  such  as  the 
degradation  of  the  groundwater  resources  and  declining  groundwater  levels. 
Drought  Management  Plans  or  other  policy  instruments  are  lacking,  and  water 
quantity  management  is  currently  based  on  “crisis  management”  rather  than  on  a 
pro-active and preparedness approach. 

The  area  has  competing  water  uses,  irrigation  being  the  predominant  one,  thus 
socio-economic  impacts  of  water  stress  are  major.  Establishing  detailed  water 
balances  provided  the  necessary  input  for  the  development  of  a  cost-effective 
optimum  water  allocation  schema  among  the  users,  considering  the  spatial  and 
temporal  availability  of  water  resources.  By  identifying  the  imbalances  across  the 
water  quantity  components  and  the  related  drivers  and  pressures  (which  can 
consequently  also  impact  water  quality)  robust  targets  were  established.  
Furthermore,  the  detailed  water  balances  guided  the  development  of  a  series  of 
demand  reduction  measures  and  interventions  which  are  based  on  a  holistic 
assessment  and  can  mitigate  water  stress  in  the  short  and  long-term.  Finally, 
projected  water  balances  as  calculated  for  3  future  climate  and  socio-economic 

59 

 
 
 
 
 
 
 
 
 
 
 
 
Key findings: 

scenarios were used to test the robustness of the selected measures, supporting thus 
climate change adaptation. 
Detailed water balances have been developed for the Ali-Efenti basin in Pinios from 
1980-2010, allowing the representation of the components of the hydrological cycle 
and catchment process along with the water demand and uses in the catchment. All 
water balance features have been calculated at monthly time step, for each of the 23 
sub-catchments  and  50  demand  sites,  allowing  the  identification  of  opening  and 
closing  stock,  and  exchange  in flows,  and  have also been compared to  a  dry  year 
(2007), a normal year (1997) and a wet year (2010). 

The  balance  between  demand  and  availability  is  negative,  resulting  in  unmet 
demand  in  all  the  23  sub-catchments  every  year,  mainly  for  irrigation  purposes. 
Unmet  demand  for  industrial  and  livestock  activities  has  also  been  experienced 
during  2004-2008,  but  at  a  much  lower level  than in irrigation.  The total  annual 
unmet  demand in the  Ali-Efenti ranges from  as  low  as  5  mio m3 (1995)  to as 
high as 114 mio m3 (2007), with an average value of 33 mio m3 over the 16-year 
period. This unmet demand is mainly attributed to irrigation, yet the industry and 
livestock  sectors  are  also  affected  during  some  years.  The  Reliability  (R)  of  the 
system in supplying the requested demand (i.e. the percentage of the time steps 
in  which  a  demand  site’s  demand  was  fully  satisfied)  varies  among  the  uses.  As 
domestic use is  top priority, water allocation to this use has a reliability of 100%. 
Reliability in the provision of water to the livestock sector is a bit lower at around 
98% and for industry around 95%.The reliability in irrigation water supply is highly 
variable and in some cases is as low as 70%: 52% of these users have R>95%, 26% 
have  a  high  R  (85-95%),  13%  have  a  medium  R  (75-85%)  and  9%  have a low R 
(<75%). 

To reduce the  unmet  water  demand  a  bundle  of  demand  management measures 
have  been  assessed  within  the  urban  and  agricultural  sectors  and  an 
optimization  process  has  been  applied  to  determine  the  most  cost-effective 
options. The urban water saving measures examined included dual flush toilets, low 
flow  taps  and  showerheads,  efficient  washing  machines,  rainwater  harvesting  and 
greywater  reuse.  In  the  agricultural  sector  a  mix  of  conveyance  and  irrigation 
methods  that  would  lead  to  increased  irrigation  efficiency,  as  well  as  deficit 
irrigation and reform of cultivated crops (% of the existing ones to new crops) have 
been  investigated.  Optimisation  of  interventions  in  the  urban  sector  indicates  a 
water  saving  potential  equal  to  26%  water  saved  per  capita.  However,  above  the 
water  saving  level  of  7.5%  water  saved  per  capita,  the  applied  measures  are 
relatively expensive, and include rainwater harvesting, greywater reuse and efficient 
washing  machines.  In  order  to  improve  the  combined  efficiency  of  irrigation 
networks a high percentage of drip irrigation and precision agriculture is required. 
Optimization  indicates  18%  reduction  of  unmet  demand  with  an  investment  cost 
(AEC)  for  increasing  irrigation  efficiency  equal  to  12  million  euros  per  year.  An 
investment above that level has insignificant impact on reduction of unmet demand. 
Where deficit irrigation is implemented unmet demand reduces dramatically (75% 
reduction  of unmet  with an  investment  cost  equal  to  11.5  million euros  per  year). 
The  optimization  analysis  indicates  a  maximum  decrease  of  agriculture  unmet 
demand equal to 18% with an AEC of 12 million euros if only demand reduction 
interventions  are  taken  into  account.  On  the  other  hand  75%  reduction  of 
agricultural  unmet  demand  is  achievable  if  deficit  irrigation  practice  is  also  taken 
into  account  –  albeit  with  a  cost  to  farmers’  production  and  hence  income.  This 
result,  although  intuitive,  suffers  from  the  problem  that,  in  practice,  farmers  that 
have  access  to  groundwater  would  use  that  instead  of  conforming  with  deficit 
irrigation practices – hence tapping into non-renewable groundwater reserves. 

60 

 
 
 
 
 
In order to derive suitable indicative targets for reducing the vulnerability of water 
resources  in  the  Ali-Efenti,  the  robustness  of  the  proposed  interventions  has  been 
assessed  against  3  future  climate  and  socio-economic  scenarios.  The  response 
measures seem to be suitable as in all scenarios a reduction of the unmet demand is 
observed.  On  this  basis,  the  proposed  indicative  targets  are  to  increase  the 
irrigation efficiency in the two main irrigation districts by 7-9% (thus reaching 
82%  and  86%  respectively),  as  well  as  increase  the  urban  water  savings  by 
6%.  These  interventions  have  a  total  cost  in  the  range  of  6.5  to  16  million  euros 
AEC  (at  current  prices).  The  investigated  solutions  will  in  fact  render  additional 
reduction  of  the  unmet  demand  under  a  Markets-First  socio-economic  scenario 
which incorporates changing the crops to more profitable and less water demanding 
ones (i.e. 15% of cotton cultivation replaced by aloe vera; 5% of maize cultivation 
replaced  by  broccoli;  10%  of  maize  cultivation  replaced  by  kiwi).  These  crop 
changes will also lead to an increase in the farmers’ income in the range of 25-30 
million euros. Thus, the key to increase farmers’ income and simultaneously reduce 
the  unmet  demand  is  the  reform  of cultivated land. Even  without  applying  any  of 
the  above  selected  solutions,  and  only  by  reforming  the  cultivated  land  a 
reduction of unmet demand of 67% can be achieved. 

To  calculate  detailed  water  balance  a  distributed  water  resources  management 
model is commonly required, at the appropriate temporal scale in order to reflect the 
variability of the water resources. In the case of the Ali-Efenti RB a model has been 
set up using the WEAP software, at monthly time steps for the period 1980-2010. In 
order to set up the node-based disaggregated WEAP model, a detailed analysis of 
the  study  area  has  been  implemented  to  post-process  all  the  data  collected  and 
create  the  necessary  input  data  for  the  model.  The  model  comprises  of  23  sub-
catchments,  8  groundwater  bodies,  6  springs,  46  runoff/infiltration  links  (carrying 
runoff  and  infiltration  from  catchments  to  rivers  and  groundwater  bodies),  57 
demand sites, 6 WWTPs, 139 transmission links (transmitting water from a surface 
or groundwater withdrawal node to a user), 70 return flow links (directing the water 
that is not consumed in a demand side to a WWTP, surface or groundwater body). 
Setting  up  such  a  detailed  model,  able  to  represent  all  the  salient  features  of  the 
water cycle/balance can be a quite complex task, especially if the necessary data are 
not readily available. In the case of Ali-Efenti, the hydrological and socio-economic 
data  were  available  at  different  spatial  and  temporal  scales,  thus  aggregation 
techniques  and  proxies  were  necessary.  Additionally,  the  model  would  have 
benefited if additional calibration points were available.  

Problems 
encountered 
related to the 
development of the 
Water Balances: 

61 

 
 
 
 
Case study #2: Tiber River Basin, Italy (ABOT project, DG ENV) 

The Upper-Middle Tiber River basin (central Italy) has an area of about 5,300 km2 
with a main channel length of 141 km. The water resources in the basin consist  of 
the main River and its tributaries, the Trasimeno lake, the groundwater, two  large 
reservoirs  and  5  smaller  ones.  The  demand  sites  are  represented  by  16  irrigation 
schemes and 24 urban nodes. 
The study area is characterized by a complex topography with an elevation ranging 
from 147 to 1,538 m asl and a mean value equal to 478 m asl. The climate is typical 
Mediterranean  with  a  mean  annual  rainfall  of  about 950  mm,  and  higher  monthly 
rainfall values generally occurring during the autumn-winter period.  

Study Area: 
Upper-Middle Tiber 
River Basin, Italy 

Which are the main 
challenges with 
regard to water 
management in the 
study area? 

The basin has extended irrigation and urban areas, while losses along the pipes are 
high (40%). For that, imbalance between demand and availability (water stress) is 
frequent,  especially  for  the  urban  sites.  Moreover,  the  decrease  of  precipitation 
observed  in  recent  years  resulted  in  a  decrease  of  the  average  flows  in  the  Tiber 
River and its tributaries. Specifically a possible declining trend of both precipitation 
and river flows has been observed and in 2000-2003 and 2007 severe water crises 
occurred within the basin. 

The need to meet domestic and irrigation demands has caused the overexploitation 
of  ground  water  supply.  As  a  consequence,  many  temporary  wells  were  installed 
illegally and their number and locations, as well as the volumes of water abstracted, 
were  mostly  unknown,  thus  not allowing  an assessment  of  the the  contribution  of 
the groundwater in drought mitigation.   

How did the 
development of 
Water Balances 
support local water 
management and 
help alleviate the 
problem? 

Most  of  the  users  of  water  resources  within  the  Tiber  River  basin  are  urban 
municipalities  and  agriculture  districts.  To  decrease  the  unmet  demand,  mainly 
observed  for  the  urban  sites,  the  implemented  water  balance  allowed  the 
development of a cost-effective optimum water allocation schema among the users.  

Based on that, different possible measures and interventions were suggested to the 
stakeholders in charge of the water resources management for the maximization of 
the  unmet  water  demand  reduction  with  the  minimum  possible  investment.  Their 
robustness  was  evaluated  for  three  different  future  climate  and  socio-economic 
scenarios which were examined and compared with the baseline.  

Key findings: 

Detailed  water  balances  were  developed  for  the  Tiber  River  basin  for  2008-2011. 

62 

 
 
 
 
 
 
 
 
 
 
 
Based  on  observed  data,  these  four  years  are  considered  to  be  representative.  In 
particular,  2008  data  are  used  for  the  water  balance  modelling  calibration,  and 
2009‐2011 data for validation purposes. 

The  target  of  the  calibration  was  to  adjust  the  model  so  that  the  simulated  flow 
resembles  the  observed  flow  data  as  closely  as  possible.  The  procedure  required 
adjustment  of  some  parameters  reflecting  the  real  hydrological,  climatic,  water 
demand and consumption or anthropogenic conditions in the study area. All water 
balance features were calculated at a monthly time step and were compared with the 
dry year 2011, the average year 2009 and the wet year 2010. 

The  higher  consumptions  within  the  Tiber  River  basin  are  for  domestic  and 
agriculture use  with  a  total  water  demand  equal to  565.07 Mm3  and  212.69  Mm3, 
respectively (for the simulation period 2008-2011). In particular, the 99.2% of the 
unmet demand derives from the urban domain and is equal to 28.48 Mm3 for 
the entire simulation period. 

To  reduce  the  unmet  water  demand,  water  saving  measures  were  assessed  within 
the urban and agricultural sectors through the development of cost-benefit curves. 

Specifically,  within  the  urban  sectors  two  measures  of  monitoring  and  leakage 
repairs  and  replacement  of  old  pipes  were  selected  along  with  four  water  saving 
measures:   
1. low flow taps; 
2. dual flush toilets;  
3. efficient washing-machines;  
4. efficient dishwashers.  

Within the agricultural sector, the selected analysed measures were:  
1. monitoring and leakage repairs, pressure control; 
2. replacement of irrigation plants (switch from sprinkler to drip irrigation). 
For  the  urban  sector,  within  the  four  water  saving  measures,  efficient  washing-
machines and efficient dishwashers were found to be less convenient from the 
economic  point  of  view  and,  as  a  consequence,  were  discarded  for  arranging  the 
cost-benefit  curve.  If  low  flow  taps  and  dual  flush  toilets  are  adopted  as 
measures for water saving and assuming a population of 50% apply them, the 
water  saving  is,  on  average,  5%  for  both  measures  with  a  cost  of  3M€  and 
43M€, respectively.  

As  regards  the  loss  rate  control  parameter  identified  in  the  two  measures  of  
monitoring and leakage repairs and replacement of old pipes, it was found that for 
the  first  measure to  further  reduce the  level  of  losses,  i.e.  to  get  a  loss  rate  lower 
than  34.9%,  which  corresponds  to  a  cost  of  about  8  M€,  the  cost  increases 
considerably. Similarly for the second measure, i.e., the replacement of old pipes, 
the maximum benefit was found by a network replacement of 10% with a cost 
of 49 M€. For higher percentages, the costs are very high and replacement of pipes 
is no longer economically convenient.  

For  the  agricultural  sector  the  analysis  showed  that  by  applying  measure  1 
(monitoring and leakage repairs, pressure control) the irrigation efficiency can be 
improved by increasing the irrigation fraction from 52.5% up to 59.3%, with a 
relative cost of about 1.5M€. To get higher values of irrigation efficiency, the cost 
increases  considerably.  Similar  conclusions  can  be  drawn  for  measure  2.  In  this 
case, the maximum benefit can be obtained by carrying out the replacement of 
90% of the irrigation system network, with a cost of 4.1 M€. 

The  robustness  and  the  sensitivity  of  the  water  balance  modelling  for  the  Tiber 

63 

 
 
 
 
 
 
 
 
River basin was evaluated for three different future scenarios which were examined 
and compared with the baseline scenario (referring to the simulation period: years 
2008-2011). The scenarios include Climate Change (CC scenario), Socio-Economic 
change  (SE  scenario)  and  a  combination  of  both  (CC-SE  scenario).  All  the 
investigated  scenarios  indicate  that  in  future  years  the  unmet  demand  will 
increase  due  to  modified  climatic  conditions  and  population  growth.  The 
increase of the irrigated area, on the contrary, does not affect the agricultural unmet 
demand which is negligible for each scenario. 

The  shape  of the  ‘Pareto front’  of  optimisation  calculated for  the  CC-SE  scenario 
suggests  that  the  unmet  demand,  which  is  expected  to  increase  in  the  future, 
could  be  reduced  by  about  14%  with  a  relative  low  cost  by  applying  the 
selected  water  saving  measures.  To  reduce  the  unmet  demand  further,  the  cost 
increases significantly. 

To  calculate  detailed  water  balance  in  the  Tiber  River  basin  a  distributed  water 
resources  management  model  was  required,  at  the  appropriate  temporal  scale  in 
order to reflect the variability of the water resources. The WEAP software was used 
at a monthly time step for the period 2008-2011. A scheme of the water consumers 
and  their  interconnection  links  was  identified  as  a  first  step  for  the  model 
development  and  a  database  with  the  information  necessary  for  feeding  WEAP 
platform  was  created.  For  the  data  retrieval,  however,  some  problems  were 
encountered, mainly due to the large number of water managers which are different 
from the ones who manage the supply. The gathered data (irrigation and domestic) 
had different formats (daily, monthly, or seasonal) according to the different water 
supply managers. Therefore, the main problem concerned the heterogeneity of the 
collected  data,  as  well  as  the  temporal  resolution.  Due  to  this  heterogeneity,  the 
simulation  period (i.e.  the period  when  all  the  data  were  available)  was  only  four 
years. 

Problems 
encountered 
related to the 
development of the 
Water Balances: 

64 

 
 
 
 
Case study #3: Vit River Basin, Bulgaria (ABOT project, DG ENV) 

Study Area: 
Vit River Basin, 
Bulgaria 

Which are the main 
challenges with 
regard to water 
management in the 
study area? 

The  Vit  River  basin  is  situated  in  central  northern  Bulgaria  with  watershed  area 
covering 3,220 km2. The river starts from the Stara Planina mountain at an altitude 
of 2,030 m, flows through the central part of the Danube Valley and discharges into 
the  Danube  river.  Within  the  catchment  there  are  two  administrative  districts  - 
Pleven  and  Lovech,  including  in  total  11  Municipalities,  7  towns  and  74  villages. 
The biggest town is Pleven - a district centre with a population of over 100,000; the 
population  of  other  towns  vary  between  2,800  and  10,600;  the  population  of  the 
villages varies between 50 and 3,800 residents. The water supply system is operated 
by two companies and it is characterized by quite a high share of non-revenue water 
(50%), mostly due to significant physical leakages resulting from the outdated pipe 
network.  There  is  a  number  of  industrial  water  consumers  concentrated  mainly  in 
two towns: Pleven and Dolna Mitropolia. The total water use within the Vit River 
Basin in 2009 was 134 million m3. The electricity and steam producing industries 
have  the  biggest  share  (63%),  followed  by  agriculture  (16%)  and  urban  (10%).  It 
should  be  noted  however  that  the  hydro  power  plants  that  belong  to  the  former 
group are situated in  a cascade thus the same amount of water is recorded several 
times.  

The  relationship  between  the  different  water  sources  and  water  users  within  Vit 
Basin  is  very  complex.  There  are  many  existing  technical  connections  (channels, 
pipes,  boreholes)  between  the  major  water  sources  and  the  different  water  users. 
Due to the seasonal fluctuations of the river flow, water abstractions directly from 
the river are mainly used for feeding the reservoirs and for hydropower generation. 
The reservoirs are built in a cascade as the upper reservoirs feed the lower ones and 
thus the same amount of water is used several times.   Industrial water supply and 
water for irrigation are mostly provided by the reservoirs. Groundwater is used for 
industrial  and  potable  water  needs.  Since  groundwater  abstraction  requires 
pumping, therefore costs for energy mean it is a costly option for water yield. That 

65 

 
 
 
 
 
 
 
 
 
 
 
How did the 
development of Water 
Balances support 
local water 
management and help 
alleviate the 
problem? 

Key findings: 

is why water imported from the neighbouring basin, transferred by gravity, is also 
used for drinking water, accounting for about 80% during recent years. 

The  area  has  a  complicated  management  scheme.  Establishing  detailed  water 
balances provided the necessary input for the development of a cost-effective water 
management, considering the spatial and temporal availability of water resources. 
The  balances  guided  the  development  of  a  series  of  demand  reduction  measures 
and interventions which are based on a holistic assessment and can mitigate water 
stress in the short and long-term. Finally, projected water balances as calculated for 
3  future  scenarios  (climatic  alteration,  specific  socio-economical  alteration  and 
combination  of  them)  were  used  to  test  the  robustness  of  the  selected  measures, 
supporting climate change adaptation. 

For the purpose of developing the water balance in the Vit basin hydrological and 
socio-economic  datasets  for  2000-2009  were  used.    The  WEAP  model  was 
calibrated  for  2009,  which  represents  an  average  year  for  water  resources 
availability. The difference between the calibrated and simulated water volumes for 
three  of  the  reservoirs  vary  between  0.45  and  6%.  The  observed  and  simulated 
monthly  flows  at  the  hydrometric  station  of  Tarnene  have  an  average  annual 
difference of less than 3%.  This goodness of fit metrics gives confidence that all the 
natural hydrological and anthropogenic factors were adequately modelled. 
The simulated monthly values by the WEAP model enable the detailed assessment 
of  the  water  resources  in  the  studied  watershed.  The  water  balance  modelling 
allowed  the  determination  of  some  parameters  that  are  required  in  the  SEEAW 
tables and which cannot be products of monitoring and reporting alone, such as: the 
potential  evapotranspiration  for  the  non-irrigated  land,  the  effective  precipitation 
and the percentage distribution between the surface and groundwater bodies of the 
non-effective precipitation run-off, the losses along the water distribution networks 
and the resulting flows to the groundwater and for evaporation; the water received 
from  other  economic  units,  the  returns  to  groundwater  and  surface  water,  the 
amount of soil water.  
The optimization results for the Vit pilot river basin show that 14% of the abstracted 
water  could  be  saved  with  low  investment  cost.  The  most  effective  measure  is  to 
reduce  leakages  in  the  municipal  distribution  network  by  applying  active  leakage 
control and installation of pressure reducing valves. The results indicate that if the 
water  losses  in  the  town  of  Pleven  decrease  by  25.25%  then  the  unmet  demand 
equals zero.  
The climatic scenario showed a threat of a decreased flow in the river system, which 
would lead to some deficit in water demand during the hot months.  The combined 
climatic  scenario  and  the  most  unfavourable  socio-economic  scenario  leads  to 
superposition of the two types of different negative impacts - climatic and increased 
water consumption as a result of significant growth in irrigation. This combination 
is the most severe among all studied scenarios with a big decrease of river flow, a 
big decrease of water volume in the reservoirs and a very significant unmet demand. 
A  set  of  mitigating  measures  were  investigated.  Two  measures  with  the  highest 
impact  were  “increasing  of  the  irrigation  efficiency”  and  “rehabilitation  of  the 
irrigation system”. The strong influence of water losses in the irrigation system is 
due to the fact that the irrigation network is also used for the transportation of water 
for hydropower production, which is the biggest user of water in the catchment. 

Problems 
encountered related 
to the development of 
the Water Balances: 

By studying the SEEAW tables, it was found that some elements/parameters of the 
tables are very difficult to fill based on observed and measured data (e.g. soil water, 
flows between the water resources from one water body to another). That is why the 
WEAP  model  was  used  to  feed  the  SEEAW  tables  with  these  very  challenging 
parameters. WEAP software was found to be a reliable tool that can easily support 

66 

 
 
 
 
 
the production of water accounts under the SEEAW methodology. 
For  complex  systems  like  the  presented  case  study,  characterized  with  multiple 
reservoirs connected in cascade, the filling of SEEAW water supply and use tables 
is quite challenging, since the reservoirs are not identified as “economic” units most 
probably because they store water and this is not considered as a “production unit”. 
Within the SEEAW platform they belong to the general category “surface water”. 
The  construction  and  operation  of  such  reservoirs  however  demands  huge 
investments and significant expenses for operation and maintenance. Therefore their 
consideration as an “economic unit” should not be neglected. 

67 

 
 
 
 
Case study #4: Mulde River Basin, Germany (ABOT project, DG ENV) 

The Mulde River Basin is located in Saxony in Central Germany and is one of the 
major  tributaries  of  the  Elbe.  It  covers  an  area  of  ca.  7,400km²  and  consists  of  3 
larger sub-basins. Besides several small and medium size cities (20k-80k inhabitants) 
the catchment is mainly rural and home to more than 1 Mio. people. 

The land use is dominated by farmland (60%) with high proportions of drainage-tiled 
areas, followed by forests (17%), urban areas (10%) and pasture (10%). The average 
annual  precipitation  is  770  mm  while  there  is  a  strong  variation  between  the  ore 
mountains (1000-1200mm) and the lower parts with 550-600mm. 

Study Area: 
Mulde River Basin 
Germany / Saxony 

Which are the main 
challenges with 
regard to water 
management in the 
study area? 

How did the 
development of 
Water Balances 
support local water 
management and 
help alleviate the 
problem? 

There  is  no  actual  severe  water  availability  issue  in  the  Mulde  catchment  as  the 
water  supply  system  is  highly  managed,  mainly  by  15  reservoirs  which  are  partly 
interconnected due to a remote water supply system. Nevertheless, climate change 
predictions suggest future heat waves and related drought risks which may force the 
dominantly  rain  fed  agriculture  towards  irrigation  systems.  Since  the  Mulde 
catchment  provides  water  supply  to  around  1.5  mio.  people,  an  increasing  water 
demand  in  agriculture  may  lead  to  water-related  competitions  and  conflicts  in  the 
long  term.  Therefore  farmers  and  policy  makers  should  develop  strategies  to  face 
future water shortage together with a potential supply priority plan. 

We  showed  that  the  water  management  in  the  Mulde  catchment  is  well  managed 
and prepared to face future challenges and thus might be a good example for other 
regions.    Nevertheless  the  supply  system  is  based  on  a  difficult  structure  of 
administrative  units  and  responsibilities.  Together  with  numerous  reservoirs  this 
complicated  the  modelling  with  regards  to  model  input  data,  management  and 
policies.  The  development  of  water  balances  supported  the  understanding  of  the 
water supply structure and thus allowed us to establish a model that is capable i) to 
simulate the multi-scale impact of measures, ii) to highlight the spatial distribution 
of  future  risks  (impact  of  climate  change  projections)  and  iii)  to  suggest 
corresponding adaptations. Furthermore, we were able to incorporate water balances 
in  a  comprehensive  model  structure  as  a  powerful  tool  to  link  water  demand  and 
supply to socio-economic factors and investigate the systems cost efficiency.  

68 

 
 
 
 
 
 
Key findings: 

We  developed  the  model  (WEAP  – Water  Evaluation  And  Planning)  representing 
the water balances for the Mulde catchment from 2000-2008 at monthly time steps. 
The  model  was  calibrated  from  2000-2006,  including  3  representative  years,  one 
very dry, one very wet and one year with average conditions. The following years 
were  used for  validation  purpose.  Calibration  and  validation  showed  with  .78 and 
.66  acceptable  coefficients  of  determination.  For  a  sound  representation  of  the 
hydrological  processes  we  applied  18  sub-catchments  representing  the  main 
reservoir  and  river  catchments.  27  demand  sites,  13  supply  catchments  and  three 
groundwater “buckets” were implemented. 

The water balance in the catchment is very positive. We could not find any unmet 
demand  -  not  even  for  the  “negative”  change  (socio-economic)  –scenario  and 
extreme  climate  change  projections.  The  percentage  of  used  water  to  available 
water  did  not  exceed  5%  at  any  stage.  This  is  also  highly  influenced  by  the  well 
operated  remote  water  supply  system  (reservoirs)  which  accounts  for  <40-80%  in 
the  regions  (65%  on  average)  together  with  a  sufficient  local  water  supply  by 
ground  and  river  water.  We  found  that  water  levels  of  some  reservoirs  might  be 
vulnerable  considering  the  change  scenarios  but  since  the  reservoirs  are  mainly 
interconnected, the supply side may easily be adapted in such cases. The strongest 
impact  was  projected  for  the  climate  change  scenario  (WETTREG  data  based  on 
IPCC  A1B)  on  river  stream  flow  showing  a  stronger  periodicity  and  related 
variations  in  discharge  (up  to  12%  +/-  change  in  some  month  on  average).  The 
region  faced  major  emigration  in  the  past  2  decades  (which  resulted  in  severe 
difficulties in handling waste water due to deficient water use). It is forecasted that 
the  population  will  continuously  decrease  by  8.7%  until  2015.  Based  on  that  we 
developed  population  change  scenarios  considering  the  effect  of  population 
dynamics by plus and minus 8.7%. The effect on the water balance was similar as 
for the climate change impact - no risk on the supply side could be identified. 

We  can  show  that  the  Mulde  River  Basin  has  a  very  advanced  water  resource 
management  system  which  is  able  to  completely  meet  both  actual  and  potential 
future  regional  water  demands.  Therefore  it  turned  out  to  be  impractical  to  apply 
optimization  procedures  for  selecting  additional  measures  to  decrease  unmet 
demand  –  since  such  a  demand  was  not  identified  in  the  simulations.  Still,  as the 
private  sector  was identified  as  the  main  water  user followed  by  the public  sector 
and  finally  the  larger  business,  we  investigated  measures  for  the  urban  water 
management  measures  as  those  may  provide  additional  benefits.  Hence,  we 
simulated the effect of rainwater harvesting considering the positive effect on urban 
flooding  and  low  flow  problems  in  wastewater  systems.  This  could  also  reduce 
supply costs from the remote system by increasing the regional water supply share. 
We could show that such measures could lead to 55 and 10  litre water saving per 
Euro  invested.  This  accounts  for  up  to  30%  of  the  total  water  demand  in  private 
households. The main issues for such systems in Germany are legal difficulties. 

Problems 
encountered 
related to the 
development of the 
Water Balances: 

The  main  issues  which  we  faced  were  on  data  pre-processing.  All  input  data  was 
available  on  very  different  spatial  and  temporal  scales  and  assigned  to  various 
administrative  boundaries.  Water  demand  and  use  data  are  often  collected  by 
different municipalities while environmental data are bound to natural borders and 
available on Federal or International levels. To synchronize that and setup a model 
able to represent such a complex structure is time consuming and demanding. Other 
data are difficult to get due to the data protection law. Reservoir management plans 
are  such  an  example,  since  they  are  used  for  supply  purpose  as  well  as  for  flood 
regulation. 

69 

 
 
 
 
 
 
There are also small scale effects on water supply/demand changes which might not 
be covered by the model. A good example is water use reduction in urban areas. If 
the  urban  water  use  falls  below  a  certain  minimum  (often  along  with  strong 
emigration  dynamics  in  addition)  the  disease  risk  from  waste  water  systems 
increases due to low flow conditions (especially in summer).  

70 

 
 
 
 
Case study #5: Arno River Basin, Italy (PAWA project, DG ENV) 

The Arno River Basin is located in the Central-West part of the Italian peninsula, 
in  the  Northern  Apennines  River  Basin  District  (ITC).  The  Arno  river  flows 
through two main cities: Florence and Pisa; many other urban centres are located 
within the basin. The total permanent population is 2,200,000. 

The Arno basin has a total area of approximately 8,000 sq. km and is bounded by 
the Apennine Range that forms an arc which extends from North to East and has 
an average elevation of 1,000 m above sea level, its highest peaks rising around 
2,000 m above sea level. Water abstraction affects both surface water (approx. 360 
Ml m3/Year) and groundwater (approx. 260 Ml m3/Year); public water supply is 
the main use (40-50%), followed by agricultural and industrial uses. 

Study Area: 

Arno river basin, 
Italy 

Which are the 
main challenges 
with regard to 
water 
management in 
the study area? 

Water  stress  conditions  are  often  recorded  in  a  wide  range  of  sub-basins  and 
aquifers recurrently prone to critical conditions due to the high variability of the 
precipitation  regime  (i.e.,  discharge  below  defined  thresholds  –  Minimum  Vital 
Flow; steady decreasing trend for aquifers). 
Concurrent uses (e.g. agricultural versus public water supply) are worsening the 
water stress conditions in sensitive areas particularly during the summer months. 
More  than  60%  of  SWBs  and  50%  of  GWBs  are  below  GES  (2013  update). 
According to the 3rd RBPM evaluation report, there is an urgent need for clear and 
specific use of alternative objectives and correct application of properly justified 
exemptions under art. 4.7. 
In general, a quantitative Drought Management Plan is needed (and is foreseen 
as one of the measures included in the updated PoM – 2nd cycle of RBMP). 
A  quantitative  evaluation  of  climate  change  impacts,  according  to  the  updated 
IPCC  scenarios,  is  necessary  in  order  to  include  in  the  above  mentioned  plan  a 
specific appraisal of the sustainability and effectiveness of measures in the RBMP, 
2nd cycle. 

71 

 
 
 
 
How did the 
development of 
Water Balances 
support local 
water 
management and 
help alleviate the 
problem? 

Key findings: 

Critical conditions are evaluated, in relation to a defined threshold for the number 
of  days  with  discharge  below  MVF,  by  defining  MVF  and  simulating  high 
resolution discharge series in every reach of the river network; this is possible for 
each sub-basin/surface water body. 
The competent authority applies a different cost policy to abstraction licenses on 
the basis of the above described classification of the water stress prone areas. 
During recent drought events (e.g.in 2012), the availability of a calibrated model, 
both for SW and for GW, delivered an operative  tool to support decision making 
for 
reservoirs’  release 
programmes). 
Water  balance  derived  parameters  are  currently  used  in  a  dedicated  Executive 
Information  System,  to  enhance  the  justification  of  exemptions  and  the  correct 
application of WFD art 4.7. 

the  different  water  management  strategies 

(e.g. 

Thanks  to  the  spatial  scale  of  the  analysis,  it  was  possible  to  define  different 
conditions  for  every  sub-basin/water  body.  The  critical  areas  (Fig.  5)  are 
concentrated in the Southern portion of the basin, which comprises the following 
left  bank  tributaries:  Chiana,  Ambra,  Greve,  Pesa,  Egola,  Era.  This  level  is  also 
critical for the upper Ombrone basin and for the entire Bisenzio basin. 

The  spatial  distribution  of  critical  areas  according  to  the  defined  threshold.  In 
red, the drainage area of the most critical water bodies. 

The results on the Arno basin as a whole and on a list of sub-basins were used, in 
the River Basin Management Plan, as the basis for the quantitative evaluation: the 
good  MOBIDIC-WRM  capabilities  to  simulate  the  major  seasonal  runoff 
characteristics and to represent temporal and spatial variability, together with the 
choice of a very detailed (daily) temporal scale, this allows a fine classification of 
water deficit status and a flexible application of government strategies. 

72 

 
 
 
Example of a modelled Duration-Discharge Curve with the comparison with the 
threshold value, in order to highlight the length of the critical period i.e. with 
discharges below MVF. 

Water  balance  derived  parameters  (average  discharge;  average  discharge  during 
the  summer  months,  number  of  days  below  MVF;  distance  from  a  reference  – 
average  –  discharge  duration  curve)  were  fed  into  an  Executive  web-based 
Information  System  that  gathers  and  connects  all  information  and  data  extracted 
from  the  RBMP  for  each  SWB:  drivers,  pressures  and  impact  on  the  WB; 
monitored  ecological  and  chemical  status,  operative  actions  related  to  the 
approved PoM.  Thus single year monitoring results and water balance parameters 
are compared to verify the possible application of art. 4.7. 

Example of the annual evaluation of the parameter “yearly percentage of days 
with discharge below MVF” for IT09CI_N002AR443fi SWB of the Northern 
Apennines District (T. Bure, natural river, 54 sq.km). The highlighted 3-year 
period is related to the most recent completed monitoring period (2010-2012) 

The model outputs have been used in the Halt desertification project (“Pilot Arno 
Water  Account”,  PAWA  project:  Arno  River  Basin  Authority,  ISPRA, 
SEMIDE/EMWIS)  which  aims  at  implementing  the  SEEA-W  tables  for  three 
specific  sub-basins.  A  preliminary  discussion  was carried out to include into  the 
Arno Water Accounts scenario-generation options based on measures and climate 
change parameters. 

Problems 
encountered 
related to the 

Data  collection.  The  choice  of  very  detailed  spatial and  temporal  scales  implies 
effort in data gathering. Hydrological data are available for long time series (more 
than  20  years)  at  a  very  precise  time  scale  and  with  a  high  spatial  granularity. 
Water  abstraction  and  return  data  are  instead  affected  by  a  higher  degree  of 

73 

 
 
 
 
development of 
the Water 
Balances: 

uncertainty  and  imply  higher  data  collection  costs  since  they  require  a  long 
validation process. In many cases, especially for agricultural and industrial uses, a 
modelled estimation at a monthly scale is the only reliable available data. 
During the implementation of the PAWA project data, collected to build the water 
account  tables,  have  been  analysed  and  validated  in  order  to  identify  gaps, 
alternatives and/or additional data sources. 

Model  calibration.  About  12  calibration  gauges  were  used  to  perform  an 
optimization  of  the  model’s  parameters.  Due  to  the  limited  time  series  with 
reliable discharge data, and to the uncertainty of flow measures for smaller basins 
during the dry (Summer) season. Therefore, the calibration of the model is still in 
progress. 
Consequently,  data  collection,  validation,  processing  and  evaluation  of  results 
require a continuous and accurate effort in order to achieve increasing confidence 
regarding the assessment of relevant water balance elements. 

Support to  EEA  update on  WA.  According  to the recommendations  expressed 
during the latest WG meeting, these processes will be carried out with the aim of 
supplying data to the EEA in the framework of their activity on WA at European 
level. 

Another relevant issue is the quantitative evaluation of uncertainty. The level of 
confidence of water abstraction and returns data is significantly lower than that of 
hydrological  data:  the  impact  of  such  a  variable  degree  of  reliability  should  be 
quantified and reported together with the estimated outputs.  

The  Arno  River  Basin  Authority  has  set  up  a  modelling  framework  for  the 
estimation of water balances using the distributed MOBIDIC package (“MOdello 
di BilancioIdrologicoDIstribuito e Continuo”). More specifically, the MOBIDIC-
WRM  (Water  Resources  Management)  tool  is  a  physically-based  model  that 
allows  the  estimation  of  the  elements  of  the  hydrological  balance  in:  the  sub-
surface  layer,  the  soil-vegetation  system  and  surface  water  bodies.  In  the 
representation of physical processes, the main innovations with respect to existing 
models  concern  the  coupling  of  the  water  balance  in  soil  and  vegetation  with 
surface energy balance (to the benefit of evapotranspiration computation and use 
of  remotely  sensed  maps  of  Land  Surface  Temperature  for  calibration  and 
validation)  and  the  detailed  interaction  between  ground  water  and  surface  water 
bodies. Geographical input data, both in raster and vector, can be supplied to the 
model  in  most  common  GIS  formats  or  as  raw  binary  or  ASCII  data. 
Meteorological  inputs  and  data  on  withdrawals,  artificial  releases  and  reservoir 
operations are fed into the model in DBF or text tables. 

A  pre-processing  step  of  the  model  (MOBIDIC-BUILDGIS)  is  devoted  to 
consolidate  the  input  of  geographical  and  time-series  data,  and  to  establish  the 
mutual  spatial  and  topologic  relationships  between  topography,  river  network, 
reservoirs and withdrawal /release points. The hydrological balance can, then, be 
run  with  MOBIDIC-WRM  with  the  desired  spatial  and  temporal resolution.  The 
output of the simulation includes time series of modelled discharge of each branch 
of the hydrographic network and related statistics (e.g. flow duration curves) and 
maps of hydrological components (evapotranspiration, runoff, precipitation). The 
output  of  the  hydrological  balance  can  then  be  linked  with  information  on 
environmental  flow  and  water  consumption,  and  the  water  balance  can  be 
computed for each branch of the hydrographic network. 

74 

Technical details 

 
 
 
 
During  the  application  of  the  methodology  to  the  Arno  basin  the  hydrologic 
simulation has been performed on a daily time scale for the period 1993-2013 (21 
years). The geomorphology of the basin and related hillslope processes have been 
modelled using a Digital Elevation Model with 10 m square cells. Information on 
land cover, geology and soil hydraulic properties has been retrieved from existing 
maps  and  remote  sensing  data.  Both  natural  (where  no  withdrawals  or  artificial 
releases have been considered) and ‘anthropic’ scenarios have been simulated. The 
results include modelled discharge time series on nearly 20,000 river branches and 
more  than  22,000  withdrawal  sites,  flow  duration  curves,  and  maps  of 
hydrological  components  over  the  basin  area  (soil  moisture,  evapotranspiration, 
infiltration). 

Meteorological input  data were  obtained from  the regional  hydro-meteorological 
monitoring  network.  Also,  water  level  measurements  for  a  set  of  stations  with 
available  stage-discharge  relationships  for  at  least  few  years  in  the  study  period 
were used for calibration and validation purposes. 

The hydrologic simulation of the whole Arno basin at 200 m resolution represents 
the scientific basis on which multi-year strategies and water balance management 
actions  are  based.    In  this  context,  the  hydrological  model  results  support 
strategies  and  plans  to  control  water  status,  in  order  to  monitor  the  volume  and 
level or rate of flow to an extent that is considered relevant to preserve ecological 
status and potential. This is the main goal of the Arno River Water Balance Plan, 
approved in April 2008. 

The  water  balance  plan  was  drafted  dividing  the  river  network  into  significant 
tracts  and  sub-basins.  Out  of  these,  44  river  sections  were  deemed  to  be 
representative and selected as underlying homogeneous basin portion in terms of 
hydrology and criticality. 

Hence, the water balance was computed, for each river branch, in accordance with 
the requirements of the Decree of the Italian Ministry of Environment dated July 
29, 2004, as natural discharge (Q) minus withdrawal (W) and Environmental Flow 
(EF): 

WB represents the “residual flow”, i.e. the flow actually available for further use, 
or, on the contrary the possible deficit. 

The  water  balance  was  drafted,  on  the  basis  of  the  MOBIDIC-WRM  results,  as 
daily  series  focusing  attention  on  the  temporal  intervals  during  which  the  most 
critical conditions can occur. 

Due  to  the  markedly  torrential  character  of  the  water  courses  in  the  basin,  that 
even  concerns  the  reaches  of  major  hierarchical  rank,  the  investigated  time 
interval  coincides  with  the  months:  June,  July,  August,  and  September.  The 
application of the above model produced discharge synthetic series for 1993-2006; 
the  results  are  expressed,  for  each  significant  section,  as  a  duration  curve  of  the 
yearly period and similar duration curves for the dry season (June-September). 

With the aim of  establishing and quantifying  the conditions of river reaches, in 
terms of maintenance of sustainable discharge values, the environmental flow was 
identified, with the use of hydrological criteria, as Q7,2, i.e. the minimum  average 
flow over 7 days with a 2 years  return time. 

The  component  that  represents  water  use  (W)  which  includes  all  abstraction 
typologies is referred to the June-September time interval. Furthermore, it includes 

75 

 
 
the  concentrated  returns  from  the  waste  water  treatment  plants.  therefore  the 
equation for average summer withdrawals is: 

where the first three terms on the right hand side are dissipative withdrawals from, 
respectively,  surface  water  bodies,  springs  and  dug  wells,  and  the  fourth  term  is 
wastewater returned to the river network. The resulting residual flow WB may be, 
in the significant river sections, either negative or positive values. 

The  negative  values  show  a  condition  of  severe  water  deficit  in  the  summer 
period,  with  flow  lower  than  Minimum  Flow  Index  for  more  than  60  days.  The 
positive values represent the average flow available for further withdrawals. The 
Arno  and  its  tributaries  are  characterized  by  a  highly  variable  regime,  closely 
linked  to  precipitation  patterns.  This  shows  that  the  most  critical  conditions  are 
concentrated  during  the  summer,  when  high  temperatures  increase  evapo-
transpiration losses. For these reasons and with the further consideration that river 
ecosystem  stress  is  mostly  due  to  prolonged  persistence  of  lean  values,  the  case 
study  was  focused  on  the  results  of  simulations  regarding  the  four  summer 
months,  during  which  all  factors  having  an  influence  on  water  balance  reach  a 
critical  phase  correlation.  To  synthesize  this  into  a  single  stress  indicator,  the 
analysis was finally focused on the number of days when  the average daily flow 
rates falls below the site-specific EF value. This number of days is derived from 
simulated (modelled) flow duration curves. Critical values were aggregated into 4 
classes , on which the earlier criticality map is also based. 

Yang,  J.,  Castelli,  F.,  and  Chen,  Y.:  Multiobjective  sensitivity  analysis  and 
optimization of distributed hydrologic model MOBIDIC, Hydrol. Earth Syst. Sci., 
18, 4101-4112, doi:10.5194/hess-18-4101-2014, 2014 

F. Castelli, G. Menduni, B. Mazzanti. A distributed package for sustainable water 
management:  A  case  study  in  the  Arno  basin.  In:  H.  J.  Liebscher,  R.  Clarke,  J. 
Rodda, G. Schultz, A. Schumann, L. Ubertini, G. Young. The Role of Hydrology 
IAHS, 
in  Water  Resources  Management,  pp.  52-61,  Wallingford: 
ISBN:9781901502947, 2009 

Campo, L., Caparrini, F., and Castelli, F.: Use of multi-platform,  multi-temporal 
remote-sensing  data  for  calibration  of  a  distributed  hydrological  model:  an 
application in the Arno basin, Italy, Hydrol. Process., 20, 2693–2712, 2006 

References 

76 

 
 
 
 
 
Case study #6: Slovenia 

The  case  study  area  is  the  whole  territory  of  Slovenia.  This  poses  quite  a 
challenge  in  water  balance  modelling,  since  Slovenia  is  located  at  the 
intersection  of  four  major  European  geographical  regions:  the  Alps,  Dinaric 
Alps, the Pannonian Basin and the Mediterranean. 

The 
four  main  macro-regions  have  very  heterogeneous  climatology, 
geographical,  geological  and  ecological  characteristics  that  create  great  spatial 
and temporal variability. 

Study Area: 
Slovenian macro-
regions 

Which are the 
main challenges 
with regards to 
water 
management in 
the study area? 

Most of the water used for water supply systems in Slovenia is from groundwater 
resources. The WFD requires groundwater quantitative assessment which is done 
in  Slovenia  with  the  use  of  a  regional  water  balance  model  as  a  key  tool  for 
groundwater recharge evaluation. 
The water management challenges depend on the water balance model as it is the 
basis for sustainable water management. The main challenges in the study area 
arise from: 
- big geographical variability in geology, relief, climate, vegetation, land use etc., 
-  big  intra-  and  inter-annual  variability  of  water  balance  elements like  seasonal 
variability  of  water  balance  elements,  highlighted  by  increased  incidence  of 
droughts and floods in recent years, 
-  large  areas  with  complex  karst  hydrology  and  hydrogeology  covering  more 
than 40% of the territory.  

How did the 
development of 
Water Balances 
support local 
water 
management and 
help alleviate the 
problem? 

The first RBMP used long term water balance as a basis and in the process it has 
been found that the yearly or even monthly water balance will be needed in the 
next RBMP cycle in order to manage water resources sustainably.  

In the WFD there is also a request for groundwater quantitative status assessment 
and  over  the  years  annual  water  balance  was  made  for  the  separation  of  total 
runoff  into  various  components.  It  allowed  us  to  quantify  and  evaluate  the 
groundwater recharge and assess the groundwater quantitative status.  

The regional  water  balance  model  GROWA,  developed  at  FZ  Jülich,  Germany, 
was  adapted  in  bi-national  cooperation  with  Slovenia.  The  GROWA  model 

77 

 
 
 
 
 
outputs  provided  the  necessary  input  to  analyse  water  abstraction  to  water 
resource ratio. 

The GROWA model was first used for long term water balance and later on for 
annual water balance calculations on a regional scale and by river basins. 

The result of the model is spatial distribution of water balance elements over the 
whole territory of Slovenia. Spatial distribution allowed us to identify local areas 
with possible problems in  water quantity. The water authority now has the data 
on water quantities that can be used for water management.  

Spatial distributed calculation of water balance elements is a useful tool both for 
regional  and  local  water  management  The  water  balance  model  allows  water 
managers to improve water planning. 

The model itself proved to be robust and flexible enough to encompass big spatial 
variability  of  water  balance  across  the  territory.  It  is  of  special  interest  that  it 
proved  reliable  in  karst  areas  with  a  scarce  surface  watercourse  network  and 
complex hydrogeology. 

Water balance enables the identification of local areas with possible problems in 
water quantity. 

Water  balance  is  also  indispensable  in  the  process  of  nutrient  flow  modelling 
which is now being analysed in Slovenia. 

Water  balance  results  are  used  on  a  regular  basis  for  national  reporting  on  the 
WFD implementation to the European Commission and for supplying data to the 
EEA. 

The  model  enables  both  calculation  of  numerical  values  of  water  balance 
components  by  river  basins  or  any  hydrological  closed  area,  and  spatial 
representation of the results in maps. So, it gives both useful graphical overview 
of  the  water  balance  and  numerical  data  for  practical  solutions  to  water 
management problems.  

The maps showing spatial distribution of water balance components means for a 
long  term  period  1981  to  2010;  precipitation,  actual  evapotranspiration,  total 
runoff, direct runoff and groundwater runoff (groundwater recharge): 

Key findings: 

78 

 
 
 
 
MEANS OF 1981 – 2010 

Precipitation: P 

Evapotranspiration: ETR 

Total runoff: QT = P - ETR = 
QD + QGW 

Direct runoff: QD 

mm/a 

1 431 

641 

790 

501 

Groundwater recharge: QGW 

289 

% 

100 

45 

55 

35 

20 

m3/s 

508 

322 

186 

Distribution of annual amounts of precipitation to water balance components 
actual evapotranspiration, surface runoff, interflow and groundwater recharge 
for 1971 to 2012, showing inter annual variability: 

79 

 
 
 
 
 
  
  
  
 
Problems 
encountered 
related to the 
development of 
the Water 
Balances 

In recent years inter annual variability has been increasing. 

It should be noted that the calculations of water balance for the hydrological year in 
the model used can vary from the calendar year. Also,  the present RBMP suggests 
that the temporal scale of annual water balance model must be downscaled due to big 
intra-annual variations of water balance elements in Slovenia. The resolution should 
be downscaled to monthly or even daily level.   

GROWA  –  GROßräumiges  WAsserhaushaltmodell  (Regional  Water  Balance 
Model)  developed  at  Forschungszentrum  Jülich,  is  a  grid  based  empirical  regional 
model consisting of several modules, enabling separation of input precipitation into 
the main water balance components: actual evapotranspiration, total discharge, direct 
runoff  and  groundwater  recharge.  It  calculates  net  water  balance  originating  only 
from precipitation at the modelled area, for a hydrological year from November 1st 
to  October  31st.  Due  to  the  modular  architecture  the  model  is  flexible  both  in  the 
calibration  process,  as  well  as  for  upgrading to  modelling  of  nutrient transport  and 
refining of temporal scale below a year. It has been adapted from the German setting 
for use in the complex setting of Slovenia. It has been calibrated  with hydrological 
data measured in the 1971 to 2000 reference period.  

Technical details 

The main features of the model are: 

•  Scale of application: 100 – 500,000 km2 
•  Spatial resolution: Variable - dependent on input grid 
•  Temporal resolution: Year (with a possibility to downscale to a finer 

temporal scale) 

•  Units: mm of water column; runoff also m3/s 
• 

Input data type: Digital data - maps 

80 

 
 
 
•  Potential evapotranspiration: Penmann – Monteith equation 
•  Actual evapotranspiration: Renger - Wessolek equation 
•  Runoff separation: Base flow indices – BFI 
•  Results: Total runoff, direct runoff (overland flow + interflow + drainage 

flow), groundwater recharge 

•  Validation: Runoff data from gauging stations (MQ, MoMNQ) 
• 
Implementation: C++, GIS – linkages to GRASS / ArcView 
Andjelov, M., Wendland, F., Mikulič, Z., Tetzlaff, B., Uhan, J., and Dolinar, M., 
(2014).  Regional  Water  Balance  Modelling  by  GROWA  in  Slovenia. 
Proceedings of Danube Conference 2014, XXXVI Conference of the Danube 
Countries  on  Hydrological  Forecasting  and  Hydrological  Bases  of  Water 
Management, Deggendorf.  

Andjelov,  M.,  Mikulič,  Z.,  Tetzlaff,  B.,  Uhan,  J.  and  Wendland,  F.  (2015). 
Groundwater  recharge  in  Slovenia.  (In  preparation),  Schr.  d.  FZJ,  Reihe 
Umwelt, Jülich.  

Frantar, P. (ed.) (2008): Vodna bilanca Slovenije 1971-2000 = Water Balance of 
Slovenia  1971-2000.:  Ministrstvo  za  okolje  in  prostor,  Agencija  Republike 
Slovenije za okolje, 119 p., Ljubljana. 

Kunkel,  R.  &  Wendland,  F.  (2002)  :  The  GROWA98  model  for  water  balance 
analysis  in  large  river  basins  -  the  river  Elbe  case  study.-  Journal  of 
Hydrology 259: 152-162. 

References 

81 

 
 
 
 
Case study #7: The Jeziorka River Catchment, Poland 

The Jeziorka River is a tributary of the Vistula River, located in the central part of its 
RBD, in Poland. The Jeziorka River Catchment is  a rather small lowland catchment 
(989 km2) with a long-term annual average precipitation of 530 mm. The area, which 
partially  covers  the  suburbs  of  Warsaw,  is  quite  densely  populated  (167 pers./km2) 
with  4  major  towns  of  4  to  42 ths.  inhabitants.  The  catchment  is  dominated  by 
agricultural land use, about 76%, of which more than half is arable. Forests cover 17% 
of  the  catchment,  and  urban  areas  –  located  mainly  in  the  downstream  part  of  the 
catchment – 7%.  

Study Area: 
Jeziorka River 
Catchment, Poland 

Which are the main 
challenges with 
regard to water 
management in the 
study area? 

How did the 
development of 
Water Balances 
support local water 
management and 
help alleviate the 
problem? 

Key findings: 

The following case is the description of the typical methodology applied in Poland. 

Intensive use of groundwater resources for municipal supply and sprinkler irrigations 
of fruit and vegetables, together with surface water abstractions for fish ponds, have 
caused  problems  with  meeting  the  environmental  flow  requirements  and  cause 
periodic water shortages. For these reasons, and also because of water quality issues, 
the Jeziorka River Catchment was indicated in the Vistula River Basin Management 
Plan as being at risk of not achieving the environmental objectives and thus requiring 
development  of  a  water  management  policy  document  (named  Conditions  for  the 
Water Use in the Catchment).  

The development of detailed water balances allowed  identification of the causes of 
water stress,  its spatial  extent  and  severity.  On  the  basis  of  balance results  a  water 
management  policy  document  has  been  developed  in  which:  i)  priorities  of  water 
uses  in  the  catchment  have  been  set,  ii)  environmental  flow  requirements  defined, 
and iii) restrictions for introducing new water users and issuing water permits have 
been  stated.  Moreover,  water  saving  incentives  and  necessary  measures  for 
improving  the  accuracy  of  the  demands  and  water  use  assessment  have  been 
formulated.  

Water  balances  have  been  developed  for  the  multi-annual  period  of  1988-2009. 
Firstly,  groundwater  balance  has  been  calculated  as  a  comparison  of  available 
resources  (renewable  groundwater  resources  minus  part  of  a  base  flow  which  is 
needed  for  maintaining  environmental  flows  during  low  flow  conditions)  and 
groundwater  abstractions  in  hydrogeological  -  water-balance  units.  Two  scenarios 
for  groundwater  balance  have  been  analysed:  i)  for  abstractions  declared  in  the 

82 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
system of water charges in 2010 (157 users in the catchment, 28.9 ths. m3/d) and ii) 
for  abstractions  allowed  by  water  permits  (79.9 ths. m3/d,  332 users,  including  210 
agricultural  users  which  did  not  then  incur  water  charges).  Within  these  balances 
correcting  factors  for  base  flow  discharges  to  the  rivers  representing  the  impact  of 
groundwater  use  in  analysed  sub-catchments  have  been  computed.  The  balance 
results  are  positive  for  the  catchment  as  a  whole,  but  local  deficits  occur  in  the 
downstream  units,  in  which  the  majority  of  abstractions  is  situated,  highly 
pronounced  in  the  ‘water  permit  scenario’  (about  14.0 ths. m3/d).  Additional, 
scenarios  are  also  analysed  based  on  the  expected  economic  development/growth 
and forecasted climate changes.  

Surface water balance has been modelled as a simulation of water allocation in the 
catchment with a 10-day time step. In the area 29 sub-catchments (see map below) 
have  been  defined  and  77  surface  water  users  have  been  identified,  including 
environmental  flow  requirements  in  each  of  analysed  balance  cross-sections,  1 
industrial  plant,  9  fish  farms  and  38  return  flows  from  municipal  groundwater 
abstractions.  

Water  resources  have  been  described  as  time  series  of  (naturalised)  mean  10-days 
flows  derived  from  water  gauging  stations.  Water  demands  have  been  reflected  by 
time series of flows or have been modelled during simulation – for the users as fish 
ponds,  whose  demands  depend  on  the  amount  of  water  previously  supplied  and 
meteorological  conditions.  Various  hierarchies  of  water  users  have  been  analysed 
during  simulation  thus  allowing  for  analysis  of  different  management  options. 
However, in the applied hierarchy the environmental flow requirements have always 
had the highest priority. 

Balance  results  for  the  ‘water  permit  scenario’  show  that  the  time  reliability 
(percentage of the time steps in which the demand – or flow requirement – was fully 
satisfied)  for  environmental  flow  requirements  differ  much  within  the  catchment  – 
from  51  to  100%  with  the  lowest  value  in  the  Mała  River  sub-catchment  of  high 
groundwater abstractions. Low time reliability values have been noticed also in  the 
upper reaches of the Jeziorka River and its tributaries, but volume reliabilities (ratio 
of total volumes of supplied water and water demands) have been much higher (96-
99%),  thus  indicating  frequent  occurrence  of  small  deficits  in  river  flows.  Time 
reliability for industrial demands has reached 94%, and volume reliabilities for fish 
farms have been rather high, 80-95%, with the lowest value in the Mała River sub-
catchment. Available surface water reserves exceeding 0.1 m3/s have been identified 
at rather low reliability, smaller than 80%, and only in the lower reaches of the main 
river.  

83 

 
 
 
 
 
 
 
 
 
 
 
The balance results have formed  a basis for development of the Conditions for the 
Water Use in the Jeziorka River Catchment. In this document the hierarchy of water 
uses have been defined, starting from the most important one: environmental flows 
and drinking water supply, industrial demands, fish farms, irrigation. The restrictions 
for allowing for new water uses in the sub-catchments with already existing conflicts 
between environmental requirements and other demands have been formulated too. 
Moreover,  a  review  of  water  permits  for  groundwater  use  has  been  recommended, 
aiming  at  more  realistic  specification  of  a  demand  value  in  permits  –  for  existing 
users  it  should  be  close  to  the  mean  values  reported in  the  water  charge  system  in 
recent years. Furthermore, metering of water abstractions for agricultural purposes, 
both  sprinklers  and  fish  farms,  has  been  proposed,  together  with  improvements  in 
reporting procedures.  

To perform balance analysis in the Jeziorka River Catchment collection of a broad 
set of data on water demands, abstractions and water resources was required. Time 
series of river flows were available for two water gauging stations, and one of these 
gauges was monitored for a short period of time, hence assessment techniques were 
used  for  water  resources  description.  Real  values  of  water  abstractions  for 
agricultural  purposes  (sprinklers  and  fish  farms)  were  lacking.  Modelling  water 
demands  for  these  kinds  of  users  was  a  reasonable  solution  and  the  selected  time 
step  of  10-days  enabled  reflection  of  temporal  variability  of  such  demands,  but 
better  assessment  of  balance  components,  such  as  evapotranspiration  or  filtration 
losses,  would  improve  the  accuracy  of  balance  computations.  Registering  and 
reporting  of  water  abstractions  with  appropriate  time  resolution  is  also  necessary. 
The  range  of  inaccuracy  in  water  use  assessment  was  clearly  illustrated  by 
comparison of volume of groundwater abstractions reported to water charges system 
and  volume  allowed  by  water  permits,  with  the  latter  2.8  times  greater  than  the 
former. 

Problems 
encountered 
related to the 
development of the 
Water Balances: 

84 

 
 
 
Case  study  #8:  Use  of  water  resource  balance  as  a  tool  for  the  assessment  of  the 
quantitative relationship between water requirements (including the minimum balance 
discharge) and water resources – example from Slovakia 

General information 

Member State(s): Slovak Republic 
RBD(s): SK 40000/Danube; SK 30000/Vistula 
Location: Slovakia 
Time period (start/end): 2010 to 2012 

1.1  Objective of the Case study 

The  study  describes  the  assessment  of  water  resources  in  Slovakia  towards  the  water 
requirements,  and  what  role  in  this  balance  the  parameter  „minimum  balance  discharge 
(MQ)“, representing the ecological flow is playing.  

1.2  Policy and management context 

The  Eflows  implementation  is  being  implemented  following  the  conclusions  of  the  CIS 
working groups. The national coordinator is the Ministry of Environment of Slovak Republic. 
Institutions participating in the preparation of River Basin Management Plans are sharing in 
the implementation of Eflows. Currently, Slovakia is re-evaluating the e-flow values and their 
implementation into the planning and decision-making processes.  

2 

DETAILED INFORMATION 

2.1  Practical Tasks (in case of methods and/or procedures) 

The Water Resource Balance (VHB) has been used in Slovakia to frame water planning since 
1973; after the implementation of WFD into the national legislation the methodology of VHB 
was  revised,  as  a basis  for  the  quantitative  assessment  of  the  water  resources.  The  updated 
methodology of VHB was elaborated by the Water Research Institute (in cooperation with the 
Slovak Hydrometeorological Institute) and approved by the Ministry of Environment in 1994. 
Legally, the VHB is supported in the Water Act  (Act No. 364/2004 Coll. as later amended) 
and its implementing regulations. Under this Act there are reporting obligations for users with 
withdrawals  or  recharges  of  quantities  higher  than  stated  limits.  The  amounts  of  the 
withdrawals and recharges reported are one of the main inputs to VHB. E-flow is represented 
by  the  value  of  minimum  balance  discharge  (MQ),  which  is  considered  to  be  one  of  the 
demand  side  inputs.  According  to  the  Water  Act  no.  364/2004  Coll.,  this  flow  represents  a 
flow,  which  allows  general  use  of  surface  water,  provides  the  functions  of  the  watercourse 
and provides protection of aquatic ecosystems in it (in short – a minimum residual flow) 

85 

 
 
 
2.2  Temporal and spatial scales 

VHB  is  performed  in  a yearly  cycle,  by  evaluation  of  the  previous  calendar  year.  The 
processing itself is made in a monthly time step. The whole territory of Slovakia is assessed, 
in the main sub-basins, using the data from a network of 137 balance profiles. The assessment 
by the sub-basins is necessary due to the complex hydrological balance of water resources as 
well as due to historical aspects (a long-term tradition of annual hydrological assessment by 
main  sub-basins).  The  balance  profiles  have  been  selected  so  as  to  cover  the  areas  with 
important influence by water uses (water reservoirs, water transfer, etc.) or which may be at 
the risk of water scarcity. 

2.3  Type of analysis or tool 

VHB  is  based  on  the  assessment  of  the  relationship  between  the  water  demands  and  water 
resources  and  its  quality  during  the  previous  year.  Water  demand  represents  actual 
withdrawals  from  the  surface  waters  and  groundwater  and  the  recharge  of  the  waste  waters 
and special waters. The aim is to make objective, factual and timely assessment and express 
the status and the possibilities for water resources utilization during the previous year and in 
this way to provide the binding basis for water management for the next period. 

The VHB has been processed separately for surface waters and for groundwater, for quantity 
and quality of water. This study further focuses on the water resource balance of the surface 
water quantity only.  

The water resource balance of surface water quantity of the past year is processed for 12 main 
sub-basins using the network of 137 water balance profiles, covering important locations for 
water  use,  influence  of  water  reservoirs  and  water  transfers  and  also  the  availability  of  the 
hydrological  information  with  the  maximum  connection  to  the  existing  network  of  water-
gauging stations. 

The utilization in the past year is the reported amounts of used surface water and groundwater 
and  recharge  of  the  waste  waters  and  special  waters  according  to  the  Water  Act.  The  limit 
values for the reporting of the withdrawals are 15,000 m3 per year or 1,000 m3 per month. 

The water management measure assessed in VHB is the effect of water reservoirs and water 
transfers.  

Water balance calculation: 

At every balance profile the following characteristics are evaluated: 

  Effect of water utilization - change of discharge - X 

   

X = V - (PO + PZO)(1) 

where: V - is the sum of recharges of waste water from the origin of the river down to 
the water balance profile, PO – is the sum of surface water withdrawals from the origin 

86 

 
of  the  river  down  to  the  water  balance  profile,  PZO  –  is  the  sum  of  groundwater 
withdrawals from the origin of the river down to water balance profile. 

  MQ – minimum balance discharge 

MQ is a discharge which represents conditions for sustainable biological activity in the river 
and  its  close  surroundings.  It  guarantees  the  general  usage  of  water  which  does  not  require 
a permission from water management bodies.  

  MPP – minimum needed discharge  

Minimum  needed  discharge  is  an  indicator  which  includes  the  water  demands  from  water 
users  (represented  by  the  change  of  discharge  X)  as  well  as  the  demands  to  guarantee  a 
minimum balance discharge MQ. 

MPP = MQ – X 

(2) 

  E – influenced discharge – is the discharge measured in a water balance profile or value 

derived from a discharge measured in a water-gauging station. 

  ENP – discharge influenced by reservoirs and water transfers 

This value of discharge is that one which would flow through the given profile, if there was 
no utilization of water but influenced by operation of water reservoirs or water transfers only.  

ENP = E - X (3) 

  C – natural discharge (scavenging) 

Natural discharge is the discharge value adjusted for the water utilization as well as for  the 
influence  of  water  reservoirs  and  water  transfers.  That  means,  this  would  be  the  discharge 
flowing through the given profile in natural conditions.  

Natural (scavenging) discharge is calculated as an influenced (measured) discharge minus the 
sum of withdrawals, recharges, influence of reservoirs and water transfer: 

  C = E - X - N - P (4) 

where  E  –  influenced  discharge,  N  –  water  reservoir  influence,  P  –  water  transfer 
influence, X – change of discharge 

  Balance status (BSC, BSENP) 

The  balance  status  is  a  non-dimensional  parameter  which  is  calculated  for  following 
alternatives: 

1.  BSC = C / MPP,(5) 

87 

 
 
 
 
 
 
 
 
 
 
 
 
The balance status of natural discharges – evaluation of what the balance situation would be 
during the natural discharges taking account of actual abstractions and discharges of water in 
the evaluated year. 

, 

2.  BSENP = ENP / MPP ,(6) 

The  balance  status  for  the  river  influenced  by  reservoirs  or  water  transfers;  in  balance 
profiles without the influence of water reservoir and water transfer BSC = BSENP. 

The following classification is used: 

BSC (BSENP)   > 

1, 1 

- category A – active balance status 

1, 1  

0, 9  

If: 

> 

> 

BSC   >  0, 9 

- category B – tense balance status 

BSC   >  0  

- category C – passive balance status 

BSC < 0 – the following values have to be tested: MPP, C: 

MPP < 0  

- category A – active balance status 

C< 0 

 - category C – passive balance status (in very special occasions only) 

  Water resource capacity - (KZC, KZENP) 

Water  resource  capacity  represents  the  value  of  the  discharge,  which  was  in  the  water 
balance profile in a given time above the value of MPP. Where the water resource capacity 
has a negative value, the water demands or the MQ requirements were not covered. 
Water resource capacity is a parameter which is calculated for following alternatives: 

1.  Natural  water  resource  capacity  –  represents  the  natural  discharge  in  the  river 

taking account of actual abstractions and discharges of water in the evaluated year. 

KZC = C – MPP, (7) 

2. 

Influenced  water  resource  capacity  –  represents  the  discharge  in  the  river 
influenced  by  water  reservoirs  or  water  transfers  taking  account  of  actual 
abstractions and discharges of water in the evaluated year. 

KZENP = ENP – MPP, (8) 

The assessment of the past year has following table form (tab. 1): 

Table  1.    Example  of  VHB  table  output:  water  balance  profile  Ipeľ  –  river  mouth, 
2012): 

Item  

 (m3/s) 

Month 

Year 

1 

2 

..... 

12 

88 

 
 
 
 
 
 
  
  
Sum of withdrawals from 
surface waters 

Sum of withdrawals from 
groundwater 

PO 

0.087 

0.113 

0.081 

0.104 

PZO 

0.086 

0.090 

0.102 

0.104 

Sum of discharging 

Change of discharge 

V 

X 

0.317 

0.309 

0.357 

0.327 

0.144 

0.106 

0.174 

0.119 

Min. balance discharge 

MQ 

0.437 

0.437 

0.437 

0.437 

Min. needed discharge 

MPP 

0.293 

0.331 

0.263 

0.318 

Influenced discharge 

Water reservoir influence 

Water transfer influence 

Discharge  influenced  by 
N+P 

Natural 
(scavenging) 

discharge 

Mean  long-term  monthly 
discharge 

E 

N 

P 

5.982 

6.593 

7.091 

4.799 

0.313 

0.400 

-0.208 

-0.095 

0.000 

0.000 

0.000 

0.000 

ENP 

5.838 

6.478 

6.917 

4.680 

C 

5.526 

6.087 

7.125 

4.775 

D  16.175 

26.711 

20.111 

18.100 

Water bearing coefficient 

KV 

0.342 

0.228 

0.354 

0.264 

Balance  status  of  natural 
discharges 

BSC  18.85 A 

18.37 A 

27.10 A  15.03 A 

Balance status real 

BSENP  19.91 A 

19.58 A 

26.31 A  14.73 A 

Natural  water  resource 
capacity 

Influenced 
resource capacity 

water 

Outputs: 

KZC 

5.232 

5.756 

6.862 

4.457 

KZENP 

5.545 

6.156 

6,654 

4,362 

assessment of the amount of the withdrawals from surface waters and groundwater, 

-  assessment of the water bearing of the year, 
- 
-  assessment of the amount of recharged waste water,  
-  assessment of the water reservoirs and water transfers,  

89 

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
-  assessment  of  the  balance  status  for  natural  discharges  taking  account  of  actual 

- 

abstractions and discharges of water in the evaluated year, 
assessment of the balance status on the streams  taking account of the effect of water 
reservoirs and water transfers and taking account of actual abstractions and discharges 
of water in the evaluated year. 

Concrete example of the outputs of VHB: 

Table 2 shows the number of water balance profiles (from all 137 evaluated profiles), which 
were  in  tense  and  passive  status  during  2010-2012.  2010  was  extremely  wet  in  Slovakia, 
followed by an extremely dry period 2011 - 2012.  

Table 2  Tense and passive states in water balance profiles in Slovakia in 2011 and 
2012 

Number of profiles 
with tense balance 
status 

Number of profiles 
with passive 
balance status 

BSC 

BSENP 

BSC 

BSENP 

0 

7 

7 

1 

5 

6 

2 

5 

9 

0 

0 

4 

Year 

2010 

2011 

2012 

The  examples  of  the  courses  of  monthly  values  of  natural  discharge,  influenced  discharge, 
water  demands  –  MQ  and  water  utilization  expressed  by  change  of  discharge  X,  as  well  as 
long-term values Qa (mean long-term discharge) and Q355 (355-day discharge) are presented 
in  Figure 1. The examples  show the situation in 2010, 2011 and 2012 in two water balance 
profiles situated close under the water reservoirs Nitrica- NitrianskeRudno (on left side) and 
Ondava – above Topľa (on right side).  

In  the  wet  year  2010  -  water  resources  can  cover  the  demands  without  any  problems. 
However  in  2011  at  the  profile  Nitrica  –  NitrianskeRudno,  the  last  third  of  the  year  the 
influenced  discharges  are  decreasing  to  the  value  of  MQ,  and  in  2012  (which  was  an 
extremely dry year) the influenced discharge was even lower than the value of MQ. This is an 
extraordinary situation, which needs an extra permission for the water reservoir operation in 
the  critical  time,  or  after  assessment  of  the  past  year  it  is  subject  for  the  revision  of  the 
measures. 

The second profile in both dry years 2011 and 2012 shows the increasing discharge influence 
of the water reservoir during low flow period, when the natural discharge would be close to 

90 

 
 
 
 
 
 
 
 
 
value Q355, but the water reservoir operation is improving the discharge situation in the river 
channel under the dam. 

Figure 1. Course of natural and influenced discharge, MQ, needed discharge MPP, change in 
discharge X – examples in 2 water balance profiles in 2010-2012 

2.4 

Information and data requirements 

The necessary inputs into the VHB are the following: 

91 

 
 
 
 
 
 
A, Withdrawals of surface waters and groundwater- are provided by the users annually in 
a  monthly  time  step  if  the  withdrawal  is  more  than  15,000  m3/year  or  more  than  1,250 
m3/month. Groundwater withdrawals are assigned to the river in the normal direction and they 
are calculated as a sum to the nearest downstream balance profile. 

B, Recharge of waste water – reported if the amount is more than 10,000 m3/year or 1,000 
m3/month. 

C, Minimum balance discharge MQ – is a water balance value, where the preferred demand 
on water resource guarantees the protection of the environment. It represents the conservation 
of  the  conditions  for  the  biological  stability  of  the  river  and  its  close  surroundings  and 
guarantees  the  general  usage  of  the  water,  which  does  not  need  the  permission  of  water 
management  bodies.  The values  of  the  minimum  balance  discharge  for  particular  water 
balance  profiles  are  determined  according  to  the  procedure  approved  by  the  Ministry  of 
Environment of the Slovak Republic.  

Determination of the minimum balance discharge MQ: 

a)  For the river reaches with regulated runoff: 

-  in  the  dam  profiles  MQ  =  Q355,  unless  it  is  not  stated  otherwise  by  operative  rules  or  by 
another reason,  

- in other reaches the value of MQ is variable, the controlled increase of runoff by reservoir is 
declining steadily down to the point where the effect of the reservoir is undetectable, and in 
that case MQ is determined according to paragraph b. 

b)  Other river reaches: 

- The minimum balance discharge (MQ) is determined as follows:  

MQ = (Qmin mes + Q100.min.d)/2   
  where 
discharges with a high level of guarantee, usually 98%. 

Qminmes  is  the  value  adopted  from  a probability  field  of  mean  monthly 

(9) 

Q100.min.d  is  the  balanced  value  of  the  minimal  mean  daily  discharge  with  the 

mean occurrence probability of once in a 100 years, determined by statistical methods.  
The value resulted from the above equation should also meet the following condition: 

½ Q364 < MQ < Q355 

(10) 

For  the  profiles  where  the  values  of  Qminmes  a Q100.min.d  are  not  available  MQ  is  determined 
according to the principles of hydrological analogy.  

The optimum determination of the values of MQ is considered to be one of the fundamental 
and complex tasks of water management. 

D,  Monthly  evaporation  from  reservoirs  –  is  calculated  on  the  basis  of  the  monthly 
evaporation and the area of the flooded surface of the water reservoir. 

92 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
E,  Mean  monthly  influenced  (measured)  discharges  in  water  balance  profiles  –  the 
discharges  measured  in  water  balance  profile  or  determined  on  the  basis  of  hydrological 
analogy from the discharge values of water-gauging stations. 

F,  Mean long-term  monthly  unaffected (natural) discharges –  representing the reference 
period  1961-2000  (used  since  2006),  serve  for  the  supplementary  assessment  for  particular 
months. 

G, Mean monthly changes of water volumes in the reservoir – are determined on the basis 
of water volume change in the reservoir between the first day of the given month and first day 
of the next month.  

The alternatives of the water reservoir activity are: 

a, The volume of the water at the end of the month is larger than at the beginning of the 
month – accumulation of the volume of water reservoir – decreasing the discharges in the 
river,  
b, The volume of the water at the end of the month is smaller than at the beginning of the 
month – discharging from the reservoir – increasing the discharges in the river, 
c, The volume of the water at the end of the month is the same as at the beginning of the 
month – the reservoir did not influence the discharges in the river. 

H, Mean monthly values of water transfer – occur in the water balance assessment in two 
ways: 

a, in the water catchment the water is transferred from,  
b, in the water catchment the water is transferred into. 

2.5  Testing of results 

The methodology is used for the annual assessment. Where there are problems, the input data 
are  determined  again,  especially  the  data  on  monitored  discharges  and  data  on  water 
utilization.  The  data  on  water  utilization  used  for  VHB  are  also  used  for  payments.  The 
balance status, evaluated permanently as passive or tense, is the signal to review the original 
measures or to set new ones. 

2.6  Current application of the method/initiative 

This  methodology  of  the  water  resource  balance  assessment  is  supported by  the  Water  Act. 
The values of the ecological flow (MQ) are being revised; according to  the actual reference 
period and taking account of the ecological and economic consequences.   

Beside  this  assessment  in  Slovakia,  the  perspective  water  resource  balances  are  also 
elaborated. These, in principle, use the prognosis of water utilization on the demand side and 
discharge characteristics with high probability of exceedance (or guarantee, in case of water 
reservoirs) on the side of water resources, or even the simulation of the discharges using  50-
year time series or more. Data series influenced by predicted climate change can be also used. 
The value of MQ can be also entered differently in the month step.  

93 

 
 
2.7  Learned  lessons  -  Conclusions  –  Recommendations  for  application  within  the 

concept of Eflows 

The Water Resource Balance makes the assessment of status after withdrawals from surface 
waters and groundwater and recharges of waste waters in previous (past) year. The data are 
obtained  based  on  the  legal  duty  of  the  users,  who  have  to  report  data  on  water  utilization 
once  a year.  The  actual  withdrawals  (not  permitted  amounts)  are  charged.  Not  all  data  on 
withdrawals are taken into account in the VHB, because if the amount of withdrawal is less 
than the limit, the data are not reported and do not enter into the evaluation of water balances. 
This leads to some underestimation of the real demands for water. 

VHB is a good tool for the monitoring of the functioning of the measures set in the previous 
period  (operation  of  water  reservoirs,  water  transfer,  etc.).  The  disadvantage  is  that  it  is 
evaluated retrospectively for the previous period, as users report the withdrawals annually. It 
is  therefore  not  possible  to  use  this  assessment  for  operational  purposes.  Following  the 
evaluation, however, if a problem is identified, the cause is looked into – if the measure is set 
in a given area, and whether it is sufficient, or whether the problem arises because of another 
reason. Then for the next programming period the measures are reconsidered. 

Contact information  
For further information, please contact:  

  LottaBlaškovičová, e-mail: lotta.blaskovicova@shmu.sk,  

tel.: +421 2 59415 274 

  Web  page,  where  the  VHB  assessments  for  previous  years  are  available  (in  Slovak 

language): http://www.shmu.sk/sk/?page=1571 

  References: 

Fekete, V.: Estimation of MQ, QZ a QR in the water balance profiles of VHB, final report of 
the task Minimum balance discharge, Water Research Institute in Bratislava, 1990, 31 pages, 
Slovak 
a  QR  vbilančnýchprofiloch  ŠVHB, 
záverečnásprávaúlohyMinimálnybilančnýprietok, VÚVH Bratislava, 1990, 31 strán). 

(Stanovenie  MQ,  QZ 

language. 

Poorová,  J.:  Methods  on  the  water  resource  balance  evaluation.  Disertation  to  obtain  the 
academic  degree  philosophiae  doctor,  in  the  study  39-41-9  Hydrology  and  Water 
management. 2007. Slovak Technical University Bratislava, in Slovak language. (Poórová, J. 
Metódyvodohospodárskejbilancie.Dizertačnáprácanazískanievedecko-
akademickejhodnostiphilosophiae doctor v odboredoktorandskéhoštúdia: 39-41-9 Hydrológia 
a vodné hospodárstvo.2007. STU Bratislava). 

Danáčová,  Z.,  Gápelová,  V.,  Lovásová,  Ľ.,  Ľupták,  Ľ.,Melová,  K.,  Podolinská, 
J.,Rischáneková, M.,Síčová, B.,Staňová, J.: Water resource balance of surface water quantity 
for 2010, SHMÚ Bratislava, 2011, 328 pages, in Slovak language. (Danáčová, Z., Gápelová, 
V.,  Lovásová,  Ľ.,  Ľupták,  Ľ.,Melová,  K.,  Podolinská,  J.,Rischáneková,  M.,Síčová, 
B.,Staňová,  J.:  Vodohospodárskabilanciamnožstvapovrchovýchvôdzarok  2010.  SHMÚ 
Bratislava, 2011, 328 strán, 15 výtlačkov) 

Lovásová, Ľ, Mgr. Melová, K., Ľupták, Ľ., Podolinská, J.,Gápelová, V., Síčová, B.,Staňová, 
J.:  Water  resource  balance  of  surface  water  quantity  for  2011,  SHMÚ  Bratislava,  2012, 

94 

 
324pages,  in  Slovak  language(Lovásová,  Ľ,  Mgr.  Melová,  K.,  Ľupták,  Ľ.,  Podolinská, 
J.,Gápelová, 
J.: 
Síčová, 
Vodohospodárskabilanciamnožstvapovrchovýchvôdzarok 2011. SHMÚ Bratislava, 2012, 324 
strán, 10 výtlačkov) 

B.,Staňová, 

V., 

Lovásová, Ľ, Gápelová, V., Podolinská, J.Ľupták, Ľ,Melová, K., Škoda, P., Liová, S., Síčová, 
B.,Staňová,J.: Water resource balance of surface water quantity  for 2012, SHMÚ Bratislava, 
2013,  324pages,  in  Slovak  language(Lovásová,  Ľ,  Gápelová,  V.,  Podolinská,  J.Ľupták, 
Ľ,Melová, 
B.,Staňová,J.: 
Vodohospodárskabilanciamnožstvapovrchovýchvôdzarok 2012. SHMÚ Bratislava, 2013, 324 
strán, 10 výtlačkov) 

Síčová, 

Škoda, 

Liová, 

K., 

P., 

S., 

95 

 
 
 
 
ANNEX II – KEY METHODOLOGICAL LESSONS FROM THE EU-FUNDED PILOT STUDIES  

Name of the Pilot project 

PAWA (Pilot Arno Water Accounts) project 

Spatial scales 

  Territory (catchment, other) covered by 

the pilot project 

  Basic unit at which the water balance has 

been set (water body, catchment, other) 

Three  sub-basins  of  the  Arno  river  basin,  which  covered  spatial 
scales as follows: 

  Chiana valley (1,373 sq. km) 
  Bisenzio valley (320 sq. km) 
 
Pisa area (407 sq. km) 

These sub-basins were identified using the following criteria:  
i) vulnerability to drought and water scarcity; ii) data availability; 
and  iii)  water  governance  structure.  Nonetheless,  data  collection 
and modelling tools took the whole Arno river basin as a reference 
area. 

Temporal scales 

  Time unit at which the water balance is 

developed  
Smallest time unit considered 

 

Temporal scales considered: 

  monthly; and  
 
yearly. 

Due to the high seasonal variability of hydrological parameters and 
anthropic activities, it is only possible to highlight the most critical 
conditions for water availability at the monthly scale. 
Hydrological  data  are  generally  available  at  shorter  time  scales 
(daily), and they can be easily aggregated. 
Abstraction/restitution data are available at a monthly scale only in 
a few cases (e.g., for industrial use in the Bisenzio basin); they can 
often  be  reconstructed  taking  into  consideration  yearly  values 
based    on  water  monthly  withdrawal  models  which  are  estimated 
for each water use.  

Accounting for the environmental demand 

The  “environmental  demand”  has  been  accounted  for  using  a 
threshold  for  the  “WEI+”  indicator  within  the  optimization 
procedure carried out for selection of measures. 

Accounting for potential desalination 

Even  if  desalination  is  taken  into  consideration  in  the  list  of 
possible  measures  for  the  production  of  SEEA-W  tables,  local 
experience  (based  on  stakeholders’  involvement  and  on  the 
analysis  of  local  water  plans)  reveals  the  limited  affordability  of 
this type of intervention. 

Accounting for potential water transfers 

Water transfers are not planned in the analysed areas and they have 
not  been  taken  into  account  as  a  potential  measure  for  the 
optimization process with SEEA-W tables. 

Information mobilized 

Hydro-meteorological  data  have  been  provided  by  the  Region  of 
Tuscany (Hydrological Service). 
Abstraction  data  have  been  provided  by  water  utilities  and 
Tuscany Provinces. 
Information  on  wastewater  treatment  plant  (WWTP)  production 
has been provided by water utilities. 
Socio-economic data have  been downloaded from ISTAT (Italian 
National Institute for Statistics) data warehouse. 

96 

 
 
 
 
 
 
 
 
Main sources of uncertainty 

Link to modelling 

The datasets with the highest degree of uncertainty are abstraction 
data for agricultural, industrial and household uses. In many cases, 
only  estimates  are  available,  based  on  permits  or  even  more 
general evaluations (e.g., extent of irrigated areas). As a result, the 
total 
and 
evapotranspiration  also  have  a  high  level  of  uncertainty.  In  the 
industrial  sector,  some  uncertainty  is  due  to  the  exploitation  of 
water  for  manufacturing  without  a  clear  distinction  between 
production and sanitary uses. 

groundwater 

irrigation 

amount 

losses 

of 

Mechanisms  for  uncertainty  reduction  are  based  on  statistical 
analysis and use of simple models (e.g., linear regression) in order 
to verify and correct outliers and biased values. 

Key  parameters  that  are  particularly  difficult  to  assess  based  on 
current data and information: 

  WWTP inflows/outflows; and 
 

storm urban catchment flows from combined sewer 
overflows. 

In  both  cases,  gathered  data  (from  WWTP  management)  do  not 
have  an  acceptable  level  of  reliability;  the  total  amount  is  often 
derived from simplified models based on precipitation over urban 
areas.  
Due  to  the  non-linear  process  of  discharge,  a  more  specific 
analysis  based  on  more  detailed  rainfall  data  and  sewer  network 
characteristics  should  be  carried  out  in  order  to  improve  these 
estimates. 

The different datasets for hydro-meteorological variables referring 
to  climate  change  scenarios  are  an  "innovative  source  of 
information".  Six  different  reconstructed  time  series,  which  were 
obtained by using three different global circulation models and two 
different socio-economic scenarios, have been used for simulating 
the impact of measures.  

A distributed hydrological model has been used in order to obtain 
physical water asset account values. The MOBIDIC-WRM (Water 
Resources  Management)  tool  is  a  physically-based  model  that 
allows the  estimation of the elements of the hydrological balance 
in  the  sub-surface  layer,  the  soil-vegetation  system  and  surface 
water bodies. 
A  lumped  groundwater  model  has  been  used  to  obtain  monthly 
data  of  aquifer  water  quantity  and  exchanges.  Both  models 
delivered  detailed  information  and  consistent  estimations  of  the 
physical quantities. 
A  Visual  Basic  Application  (VBA)  tool  for  MS-Excel  has  been 
produced  by  the  PAWA  partners  to  automatically  compile  the 
SEEA-W  Physical  Use  &  Supply  tables  (PSUAT)  and  the  Asset 
account  tables.  Thus,  it  is  possible  to  perform  the  compilation  of 
tables and the production of thematic graphs in a quick and reliable 
way  directly  using  the  data  stored  in  the  Geo-Database  that  has 
been developed and populated for the project activities. 

Socio-economic indicators estimated 

Due to their insufficient number and reliability (at the level of each 
sub-basin  studied),  detailed  socio-economic  indicators  have  not 
been integrated into the water balance framework. 

Main management scenarios investigated 

Many “management scenarios” have been analysed using the water 
balance, combining 16 different measures for general purposes or 
for specific uses (e.g., reducing leakages,  awareness, reuse,  water 

97 

 
 
 
 
 
 
  
 
Other  specific  challenges  met  when  developing  the 
water balance 

General comments  

saving devices, green measures, tariffs). 

For  both  the  Chiana  and  the  Bisenzio  areas,  the  interaction 
between  surface  water  and  groundwater  plays  a  role  in  the 
estimation of water availability and evaluation of the effectiveness 
of water saving measures. The possibility to improve groundwater 
modelling  (for  the Prato  aquifer,  connected  to  the  Bisenzio  river) 
allowed a better understanding of the relationship and highlighted 
the  need  of  a  similar  application  for  every  groundwater  with 
strategic water storage and high abstraction pressures. 

  Water accounting is a good supporting tool for water 

 

 

quantitative management with stakeholders. 
It is well suited to generate scenarios to assess the impact of a 
combination of measures. 
It also highlights the need to improve knowledge and data 
management between stakeholders. 

98 

 
 
 
 
 
Name of the Pilot project 

ASSET (Accounting System for the SEgura river and Transfers) 

Spatial scales 

  Territory (catchment, other) 
covered by the pilot project 

  Basic unit at which the water 

balance has been set (water 
body, catchment, other) 

The study basin corresponds to Segura River Basin (SRB, Spain), with an area 
of  18,870  km2,  located  in  the  south-eastern part of  the  Iberian Peninsula.  The 
basic unit at which the water balance has been set corresponds to exploitation 
systems. Therefore the basin was discretized in seven representative elementary 
watershed  management  units  considering  aggregation  of  ECRINs  units  and 
sub-basins. This basin has the lowest percentage of renewable water resources 
of  all  Spanish  basins  and  is  highly  regulated.  The  main  water  demand  comes 
from agriculture, covering more than 43% of the basin surface, of which one-
third  is  brought  under  irrigation  (269,000  ha).  It  should  be  emphasized  that 
agricultural water demand from irrigated areas of the SRB accounts for 85% of 
the  total  water  demand  in  2007  in  the  entire  basin.  Water  scarcity  is  a  major 
issue in the SRB. Available water resources per inhabitant in the SRB (only 442 
m³/inhabitant/year) are  much lower than the national water scarcity threshold, 
which  is  set  at  1,000  m³/inhabitant/year,  according  to  United  Nations  and  the 
World Health Organization. The difference between water supply and demand 
is  high.  Consequently,  two  water  transfers  together  with  desalinization  are 
considered the most attractive options to increase water availability in the basin. 
The  problems  of  water  scarcity  and  droughts  are  persistent  in  the  basin, 
affecting the economy of the region and generating water conflicts between the 
final users (irrigation communities, etc.). 

Temporal scales 

  Time unit at which the water 

balance is developed  
Smallest time unit considered 

 

Location of SRB and spatial disaggregation 

The  time  discretization  was  set  up  at  the  monthly  scale.  The  time  period 
corresponds to 2000-2010. 

Accounting 
demand 

for 

the  environmental 

The environmental demand was considered according to the water planning of 
the basin (SRB water planning). The water agency (CHS) provided these data, 
and the methodology applied is described in the water plan of the basin. 

Information mobilised 

The  main  data  source  was  the  Confederación  Hidrográfica  del  Segura  (water 
agency).  This  water  agency  provided  data  from  meteorological  and 
hydrological networks, such as the automatic SAIH system (Automatic System 
of  Hydrological  Information),  manual  networks  of  rain  gauges  and  stream 
gauges (ROEA), and other additional information. Digital information below a 
GIS  was  also  provided,  such  as  SRB  limits,  channel  network,  groundwater 
bodies, reservoirs, wetlands & protected areas, aggregated demand units, and so 
the  estimation  of  actual 
on.  Satellite 
evapotranspiration,  and  results  from  a  rainfall-runoff  model  (SIMPA)  were 
collected. 

images  were  analysed 

for 

99 

 
 
 
Main sources of uncertainty 

Link to modelling 

Socio-economic indicators estimated 

Main 
investigated 

management 

scenarios 

Other  specific  challenges  met  when 
developing the water balance 

General comments  

The  principal  uncertain  physical  water  balance  components  are:  groundwater 
recharge  and  soil  moisture.  The  actual  evapotranspiration  (AET)  cannot  be 
based  on  direct  measurements,  but  need  to  be  modelled.  A  combination  of 
remote  sensing  information  and  hydro-meteorological  networks  are  needed  to 
quantify physical  water balances  for adequate decision  making.  Appropriately 
calibrated hydrological models could be a valuable tool. These methods allow 
an  objective  assessment  of  water  demand  and  water  consumptive  use  and  the 
impact  of  measures,  to  support  an  economically  and  environmentally 
sustainable future of Mediterranean agricultural basins. 

Remote  sensing  AET  retrieval  algorithms  were  applied  for  assessing  the 
corresponding  inputs  to  the  tables.  The  model  applied  is  based  on  vegetation 
indices estimated from MODIS satellite images. 
In  first  instance,  the  SIMPA  rainfall-runoff  model  was  considered  for 
estimation of inputs to the ASSET table, such as AET and soil moisture.  The 
comparison between the time evolution of AET estimated from remote sensing 
and that simulated by the model, demonstrates a bad performance of the model 
in  the  estimation  of  this  variable.  Therefore,  the  model  outputs  were  not 
considered as input to the tables.  
One  way  for  strengthening  the  robustness  of  the  water  balance  developed 
considering  a  rainfall-runoff  model,  is  to  modify  the  structure  of  the  model. 
Spatial  calibration  of  the  model  on  the  basis  of  AET  estimated  from  remote 
sensing  is  a  way.  Another  possibility  is  considering  remote  sensing  AET 
retrieval as input to the model (instead of potential evapotranspiration). In that 
case, on the one hand the uncertainties will be reduced and on the other hand 
the accuracy in the results will be higher.  

Economic  information  is  partly  available  for  administrative  regions  that  are 
away  from  river  basin  territory.  Data  quality  could  be  improved  if  statistical 
economic information can be adapted to the river basin activities. The nature of 
economic data (yearly information) cannot be transformed to monthly or daily 
data  without  introducing  bias.  Therefore,  the  economic  outputs  from  the 
ASSET  project  will  be  at  an  annual  scale  and  for  the  whole  basin.  Economic 
indicators  suggested  by  the  SEEAW  methodology  will  be  assessed  for  the 
Segura River Basin.  
At the basin scale, some indicators have been estimated: one related with Water 
Productivity  (WPe),  and  others  related  with  the  cost  of  supplying  water, 
Implicit water price (IWP) and Implicit wastewater treatment price (IWTP), the 
Average water supply cost (AWSC) and the Average wastewater treatment cost 
(AWTC). 
Also,  by  industry,  others  indicators  have  been  estimated  in  order  to  show  the 
differences among water users sectors. Thus, additional information is collected 
by  the  indicators:  Water  Productiviy  (WPi)  Average  water  supply  cost 
(AWSCi)  and  the  Average  wastewater  treatment  cost  (AWTCi).  Finally,  the 
Added Values by unit of water used have been estimated (AVWUi). 

In order to extract indicative target levels of water availability and usage, and 
potentials  for  water  saving  and  increase  in  the  resilience  of  the  Segura  River 
Basin (SRB) against future water shortages,  three critical issues are addressed: 
- The calculation of a set of use-to-availability indicators at the sub-basin scale 
from the SEEAW tables. 
- The analysis of the effects of a 4-year drought period on the use-to availability 
patterns observed at the basin, and  
-  The  impact  evaluation  of  various  water  management  measures  on  water 
shortage taking into account climate change and population growth. 

In  many  Mediterranean  basins,  the  agricultural  sector  is  the  main  water  user, 
and provides a significant role in the local economy. Basin-level physical water 
balances are often well studied in these regions given their importance and the 
recurring  drought  events.  But  to  target  measures  that  support  sustainable 
agricultural  water  use  in  agriculture,  it  is  necessary  to  understand  the  water 
balance at a finer scale than the basin scale.  

The  project  is  not  yet  concluded.  Therefore,  more  specific  information  about 
these  topics  will  be  included  at  the  end  of  the  project.  The  following  figure 
(Sankey  scheme)  represents  a  summary  of  water  accounting  in  the  SRB  in 

100 

2000. 

101 

 
 
 
 
Name of the project 

SYWAG: Guadalquivir River, Spain 

Spatial scales 

  Territory 

(catchment, other) 
covered by the pilot 
project 

  Basic unit at which 

the water balance 
has been set (water 
body, catchment, 
other) 

Temporal scales 

  Time unit at which 
the water balance is 
developed  
Smallest time unit 
considered 

 

Accounting 
environmental demand 

for 

the 

The Guadalquivir is the longest river in Southern Spain, with a  length of around 650 
km. The basin drains 57,527 km² with a population of 4.2 million, flowing south-west 
into the Gulf of Cadiz (Atlantic Ocean). The total length of the river and its tributaries 
are around 10,700 km. Its middle reaches flow through a populous fertile region at the 
foot  of  the  Sierra  Morena,  where  its  water  is  used  mostly  for  irrigation.  The  lower 
course of the Guadalquivir river passes through extensive marshlands (Las Marismas) 
that  are  used  for  rice  cultivation.  The  Guadalquivir  river  is  tidal  up  to  Seville, 
corresponding to 80 km upstream capable of navigation for ocean-going vessels. The 
basin  is  heavily  regulated  (volume  of  reservoirs  is  8.6  Km3,  and  average  renewable 
resources  is  5.7  Km3).  The  resources  have  been  managed  centrally  by  the  Water 
Authority since 1920's. Therefore, the management scale is the basin itself. 

The spatial scale considered for the SEEA tables has been the whole basin. 
For building the water balance tables, the spatial scale has been units of 1km2.  
The time unit for hydrological variables analysis is  a  month. Tables have aggregated 
data on a yearly basis for presentation of balances and economic data. 

The “environmental demand” has not been specifically accounted for as it is already a 
constraint  set  in  the  hydrological  plan  and  Spanish  law  makes  compulsory 
requirements at the time scale in L/sec and spatial scale of water  mass, so that SEEA 
tables are not practical at this scale. The water balance at a monthly level gives enough 
water  resources  to  fulfil  the  environmental  constraint  with  enough  margin  (monthly 
resources) 

Information mobilised 

Variable                                                      Data source 

                       INE 

                                                   SIMPA monthly 

                                      SIMPA monthly 
                       SIMPA monthly 

         INE/MAGRAMA 
                                      MAGRAMAEDAR 

                                                    SIMPA monthly 
                                                    REDIAM 

         MAGRAMA (province) 
         Evaporation stations 
         CHG 
                       CHG 

Population (municipal) 
Industrial activity by ISIC/location  
Metropolitan area 
MAGRAMA 
Agricultural production by branch 
Evaporation rate from reservoirs 
Agricultural surface evolution 
Volume in reservoirs  
Rainfall 
Rainfall 
Infiltration 
Potential evaporation ETP  
ETR 
Groundwater runoff 
Irrigation efficiency by units (1) 
Irrigation efficiency by units (2) 
Irrigation use (water doses) 
                                     SIMPA monthly 
Surface runoff 
                                    SIMPA monthly 
Temperature (1) 
Gauging stations 
                                    SAIH/Gauge monitoring network 
                                              Groundwater resources, aquifer characterization 
Volume of dam/regulation capacity 
Water demand 
River flow 
Returns 
Aquifer level (piezometric) 
Agg ECRINS 
ANyECRINS 
FEC ECRINS 

                                    CIRCA 
                                    CIRCA 
                                CIRCA 

        Inventario regadíos (CHG) 
        CHG 

                                     CHG 
                                     SAIH 

                      Piezometric monitoring network  

                                                   CHG 

                      Inventario regadíos 

                      SIMPA monthly 

        CHG 

102 

 
 
                                       
  
                                CIRCA 
                                CIRCA 
                                CIRCA 

  CHG 
                               SIMPA, Own calculations 

                                            PHC, Survey water services, Own calculations 
                                            Own calculations based on IPH 

GAZ ECRINS 
River ECRINS 
TR ECRINS 
CORINE CIRCA 
Urban water water treatment                   CIRCA 
  USEPA 
Urban runoff DBO5 concentration 
Urban runoff volume 
                 Own elaboration 
Census Discharges                                 CHG 
Red ICA/DMA (water quality) 
Abstraction 
Use 
Returns 
Consumption 
Intermediate consumption   
Gross Value Added                               Regional Accounts 
Gross fixed capital formation                 Regional Accounts, WB investment series 
Clossing stocks of fixed assets 
Water self-service production cost:       Groundwater, Ministry Report 
Water self-service production cost:       Surface Water tariff 
Water self-sanitation 
Government account table 
                                                          WB investment series 
Specific transfers 
                                                         WB investment series 

                              Own calculations based on CHG 
                I/O Tables regional 

               Survey water services 
               Administration budget (2004-2008),  

                             Admin. budget (2004-2008),   

Water tariff, Admin.budget (2004-2008) 

Main sources of uncertainty 

Link to modelling 

SYWAG  has  developed  tables  for 2004-2012  at  a  monthly  scale  and  aggregated  at  a 
yearly scale. The evaluation of hydrological data is based upon the SIMPA model and 
ETP is based upon evaporation measures in the basin. The uncertainties are reasonable 
regarding the nature of hydrological models. 

It is based upon SIMPA (official Ministry  model for water resources evaluation) and 
complemented SIMPA for agricultural land water consumption (irrigated and rain fed 
agriculture). Some specific models have been developed for urban water runoff. 

Socio-economic 
estimated 

indicators 

Socioeconomic  indicators  have  been  included,  specifically:  gross  added  value  per 
sector, intermediate consumption, financial issues and specifically a  methodology  for 
cost recovery indicators have been developed based upon the SEEA tables. 

Main  management  scenarios 
investigated 

SEEA tables have been developed for 2004-2012 including a severe hydrological and 
climatic  drought  (2005-2008)  and  two  climatic  droughts  (years  2009  and  2001)  that 
have  been  managed  by  the  use  of  reservoirs  and  groundwater.  Simultaneously  the 
impact of 'modernization' (water saving investment) has been observed in the period 

Other  specific  challenges  met 
when  developing  the  water 
balance 

There is a close relationship with the Water Agency that has included SEEA Tables in 
the Basin Hydrological Plan. Two workshops with the Segura Basin project have been 
held.  Information is available in the University of Cordoba Library services (Helvia): 

http://hdl.handle.net/10396/12557  

General comments  

SEEA tables are a good instrument for standard presentation and analysis of economic 
information included in the WFD and required for reporting. It can be used for Basin 
Characterization (Art 5 WFD) and for Cost recovery  analysis (Art 9 WFD). It can be 
used also for scenario building. The level of analysis of SEEA tables is adequate for 
basin  /sub-basin  analysis  but  (in  our  opinion)  it  cannot  be  used  for  water  mass  and 
environmental  flow  analysis  because  the  level  of  scale  is  not  adequate  to  the  SEEA 
methodology. 

103 

 
 
 
 
Name of the Pilot project 

Pilot project on water balances in the Tagus river basin, PROTAGUS 

Spatial scales 

The  transboundary  basin  of  the  Tagus,  with  a  surface  area  of  81,447  km2  (55,781  km2  in 
Spain and 25,666 km2 in Portugal). The total population in the Spanish basin is 7,833,089 
and in the Portuguese part is 3,485,816. 

Data  collection  has been  set  at  Water  Management  System  (WMS)  level  because  the  data 
are  available  at  this  scale.  However,  the  water  balances  has  been  set  at  river  basin  scale 
(separated  for  Spain  and  Portugal)  because  the  relationship  between  groundwater  and 
surface water and the economic data are not well adapted at WMS. 
Water Management System in the Spanish part are: 
1.  Cabecera (surface area: 9,400.94 km2) 
2.  Tajuña (surface area: 2,593.27 km2) 
3.  Henares (surface area: 4,134.96 km2) 
4. 
5.  Alberche (surface area: 4,103.64 km2) 
6.  Tajo izquierda (surface area: 8,321.64 km2) 
7.  Tiétar (surface area: 4,459.24 km2) 
8.  Alagón (surface area: 4,409.08 km2) 
9.  Árrago (surface area: 1,021.13 km2) 
10.  Bajo Tajo (surface area: 10,826.35 km2) 

Jarama-Guadarrama (surface area: 6,510.55 km2) 

Temporal scales 

The period of study has been 2001-2010 (accounting year). 
The hydrological data have been collected at a monthly scale, but the balance has been set at 
an  annual  scale  because  the  economic  data  and  behaviour  of  groundwater  (lag  time  and 
inertia) are best suited to adapt at the annual scale. 

Accounting 
environmental demand 

for 

the 

The “environmental demand” has not  been accounted for in the water balance. 

Information mobilised 

See Annex 1 

Main sources of uncertainty 

  Data  robustness  depending  on  source  and  no  recorded  data  for  some  parameters 
needed  to  develop  water  accounts.  The  proposed  solution is  to  manage  the  most 
reliable data (in agreement  with  the Tagus River Basin  Authorities). In addition, 
and when needed, the team will take into account aggregated data or models (e.g. 
simulation model for natural regime). 

 

For the development of water accounts, data uncertainty should be considered and 
even calculated for practical reasons. When data  are not systematically measured 
(lack of instruments or economic resources), hydrological models and estimations 
are necessary (e.g.  for urban abstractions indirect estimations are made based on 

104 

 
 
 
 
 
population  and  well  measured  consumption  volumes,  for  agricultural  demand 
estimations are made based on remote sensing). In addition, there is some danger 
of accumulating errors if these are present in different variables. 

 

Source  data  (heterogeneous  database):  multiple  sources,  many  formats  and  raw 
data, diverse units of measurement, different spatial and temporal scales. Data are 
arranged, organized and transformed (Standardized data). 

  The  same  parameters  were  sometimes  monitored  from  different  entities  and 
sometimes  with  different  tools  (several  series  exist).  The  approach  has  been  to 
cross-check the series, determining if there were large discrepancies. 
  Lack  of  standardized  method  for  initial  stock  estimations  (river  resource 
analysis).  Further  analysis  of  the  advantages  and  disadvantages  of  the 
methods  for  ordering  river  networks,  the  geomorphological  identification 
required to define the geometry, and the necessary measurements to estimate 
current  flow  levels.  Meanwhile,  a  certain  level  of  uncertainty  affects  River 
initial stocks in SEEAW. 

  Available renewable resources in aquifers lack detail (groundwater resources 

analysis). The piezometry relative evolution is used. 

  Soil  water  resources:  a  large  component  of  resources  but  with  high 

uncertainty. 

  Difficult  definition  of 

interaction 

flows  along  continental-transition 

boundaries. 

  International  watersheds:  closer  cooperation  in  the  common  definition  of 
climatic  and  hydrological  datasets.  Foster  WISE  assumption  as  a  common 
framework for international basin’s data. 

  Losses  in  distribution:  have  been  estimated  based  on  previous  supplier’s 

studies. 

  Economic  data:  no  direct  sources  of  data  for  filling  hybrid  accounts. 
Downscaling  statistics  (NUTS  level  3  in  Europe).  Regular  measurement  of 
GVA  to  identify  trends  and  compare  basins  /territories.  Serious  obstacles 
when  analysing  past  series.  Risk  of  applying  own  calculations,  unless 
statistics institutes conduct retropolation for past series. 

  Investment  records,  infrastructure  inventory:  complex  distribution  of  funds 
between government agents and lack of unified records presents some risks of 
double  accounting.  Requires  common  commitment  to  integrate  budgets  in 
WISE framework. 

SIMPA:  The  support  of  hydrological  models  facilitates  the  process  of  computing  each 
component  of  the  water  cycle  from  the  atmospheric  level  to  the  core  ones  of  hydrology 
(surface runoff, infiltration, groundwater runoff…), especially on the case of the distributed 
Spanish  model  SIMPA,  in  contrast  with  the  aggregated  simple  Témez  in  Portugal,  which 
does not allow flexible GIS treatment. 
AQUATOOL: The existence of a Decision Support System (DSS) model like the Spanish 
AQUATOOL, DMA provides a user-friendly base to geographically compile and integrate 
hydrological  variables  with  use  and  supply  units.  In  this  way,  detailed  geographical 
compilation of uses/demands enable the interpretation of Water assets in smaller scales than 
the basin (like the WMS or Hydro-Enviro Regions proposed). 

Link to modelling 

Socio-economic 
estimated 

indicators 

Socio-economic indicators have been integrated into the water balance framework. GVA has 
been taken as the main basis for the socio-economic characterization of the basin. 

Main 
scenarios investigated 

management 

The study was made on the 2001-2010 series, so that the simulation has been made on real 
measured data and not on future scenarios. It has studied management in wet years and dry 
years. 

Other  specific  challenges 
met  when  developing  the 
water balance 

The  PROTAGUS  project  has  provided  an  opportunity  to  test  and  check  the  feasibility  of 
applying  the  SEEA-W  to  produce  water  accounts  in  the  Tagus  River  Basin  District.  The 
results obtained have helped to assess, in a retrospective way, water availability, abstractions 
for economic uses, storage capacity of specific elements within the system (reservoirs, lakes, 
groundwater  bodies)  and  determine  how  pertinent  water  management  practices  have  been 
during the studied period (2001-2010). 
By  assessing  a  whole  decade,  the  relevant  phenomena  and  general  trends  could  be  easily 
discerned. A summary of the analysis conducted is included below: 

  The relationship between groundwater and river (GW-River interaction). 

  The importance of soil water resource for the rainfed agriculture and forestry. 

105 

  Analysis of dry episodes. 

  Anthropogenic pressure on water resources (abstractions, water quality) 

  The importance of hydropower cannot be shown with SEEA-W system unless the 

lack of definition on economic statistics for hydropower by INE is solved. 

  The difficulty to make the study in a transboundary river basin. There were serious 
obstacles within Portuguese RBD territory caused not only by the lack of data due 
to the crisis, but also, and more importantly, due to the lack of coherence between 
Portuguese and Spanish datasets in several fields (climatic: temperatures, rainfall, 
ETP…) as well as with the hydrological variables. As each country tends to use its 
own traditional units system, criteria to determine the WMS or use of hydrological 
models to characterize the basin, at least some effort to synchronize the results of 
its own basin analysis should be addressed under the Wise and Inspire European 
frameworks. 

  No direct sources of data for filling hybrid accounts: Economic data gathering and 
systematic  collection  still  need  large  improvements.  In  many  cases,  the  data 
gathering process at different scales (for instance at regional level by the National 
Statistics  Institute)  poses  great  difficulties  for  obtaining  reliable  numbers  at  the 
basin level. 
  Lack of economic data available and in different scales. 
  Lack of investment records and infrastructure inventory. Complex distribution 
of  funds  between  government  agents  and  lack  of  unified  records  presents 
some risks of double counting.  

  Water balances results can be useful in the application of agreed indicators (WEI 

& WEI+) or for Eflows calculations. 

General comments 

The  overall  assessment  of  the  PROTAGUS  project  is  very  positive.  The  performance  and 
achievement of outputs turned out to be very close to what was initially expected.  
Some of the obtained benefits are summarised below:  

  A  closer  collaborative  relationship  was  established  between  EVREN  and  CHT. 
This  project  allowed  for  even  closer  collaborative  work  among  the  teams’ 
members,  exchange  of  ideas  and  fruitful  discussions.  This  is  extendible  to  EC 
officials: the project allowed for frequent communications, meetings and exchange 
of ideas with representatives from the DG Environment, which led to information 
sharing  to  improve  work,  to  review  the  EEA’s  exercise,  and  discuss  future 
collaborations.  

  The  partners  gained  further  knowledge  on  the  status  of  the  Tagus  RBD, 
environmental accounting and water balances development as the project allowed 
for hands-on experience of these issues and practical application (direct use of UN 
tables).  

 

PROTAGUS  has  been  working  in  depth  on  the  economic  issues,  which  has 
allowed  EVREN  to  obtain  an  exhaustive  knowledge  about  the  gaps  and 
inconsistencies in the economic datasets from the hydrological datasets, as well as 
to perform an assessment of the economic activities involved in the Integral Water 
Cycle. 

  The  partners  had  a  chance  to  broaden  their  experience  in  water  accounting,  to 
show their expertise in information sharing and dissemination practices and gained 
visibility  from  networking  and  participation  in  events.  With  the  participation  of 
EVREN  in  the  “2nd  Mediterranean  Water  Forum”,  the  lessons  learnt  on  this 
practical case will also be valuable for other river basins around the Mediterranean 
for developing national and regional water information systems that could deliver 
the data required to fill-in the water accounts. The project consolidated its role as a 
main tool of exchanging water know-how in the Euro-Mediterranean region. 

  As for benefits for each specific party:  

 

 

EVREN  had  extensive  previous  experience  in  participating  and  leading 
international contracts and projects. In addition, it is the second time that the 
team  was  in  charge  of  a  grant  from  the  EC.  The  team  improved  skills  in 
public data scrutiny processes, hydrological models and data representation, 
using the new approach of SEEA-water. 
In this project, there have been a better contacts and information exchanges 
with other similar funded projects, particularly with regards to the SYWAG 
project  of  the  University  of  Cordoba.  For  EVREN's  team,  the  experience 
can  be  described  as  very  enriching,  especially  on  the  assessment  of 

106 

 

economic issues, due to the fact that the SIWAG team has experts on this. 
Their input and support to our project have been very fruitful. 
For  the  Tagus  River  Basin  authorities  the  compilation  of  data  required  to 
produce  water  balances,  allowed  the  team  to  homogenize  information 
coming  from  different  sources  and  databases,  and  progress  toward  their 
integration in the Hydrological Information System. In addition, this project 
confirmed  the  need  for  integration  of  the  economic  issues  into  the 
hydrological balances, as  well as having direct  measurements of the water 
uses taking place in the basin. Regarding the final results, the CHT now has 
a  validated  methodology  and  the  corresponding  tools  to  develop  and 
produce water accounts which could be integrated in hydrological planning.  
The results of the SEEAW accounting system of the Tagus River Basin District, might for 
instance, help in assessing measures of the River Basin Management Plan and the existing 
Drought Management Plan, improve demand estimations and facilitate any adjustments for 
environmental protection, management and control, demand and supply, or management of 
non-conventional  sources  (e.g.  from  waste  water  reuse).  In  addition,  they  provide  a 
standardised  representation  of  data,  which  could  facilitate  auditing,  and  comparison  with 
other SEEAW-studied basins and with the next editions of the accounts. 
In  river  basins,  such  as  the  Spanish  RBD  studied,  where  there  are  robust  hydrological 
models  and  a  long  tradition  of  collecting  management  related  data,  it  will  be  possible  to 
achieve this type of analysis. However, in those with less reliable information, the difficulty 
in  developing  water  accounts  can  be  high,  and  may  lead  to  imprecise  results.  Therefore, 
there is a need to obtain a consistent and reliable set of both hydrological and economic data 
at the river basin or sub-basin level on sectoral demands, and progress towards a long-term 
application to increase their effectiveness. 
Any  progress  towards  obtaining  and  applying  reliant  hydrological  models  and  data 
collection  related  to  water  accounts  implementation  in  those  basins  that  currently  lack 
appropriate  tools,  will  involve  economic  investments  which  should  be  considered  and 
assessed  by  policy  evaluators.  Most  of  the  hydrological  information  can  be  supplied  by 
global models, but that will not be the case for data on abstractions, returns, flows in altered 
regimes,  and  the  relationships  between  the  various  elements  with  groundwater  –which 
require a detailed and local knowledge. 
Additional  future  steps  to  be  taken  that  would  enrich  the  exercise  and  provide  additional 
inputs  to  water  managers,  statisticians,  and  economists  include  working  towards  the 
production of specific water quality tables and valuation of water resources as presented in 
the  second  part  of  the  SEEAW  manual.  That  would  provide  a  better  understanding  of  the 
socioeconomic impact of pollution and the weight of water use in goods, as well as the blue 
and green footprints of activities or the environmental services of water ecosystems. 

107 

 
 
 
Name of the Pilot project 

New  developments  in  Water  Accounts  implementation  in  Guadiana  River  Basin 
GuaSEEAW+ 

Spatial scales 

  Territory (catchment, 
other) covered by the 
pilot project 
  Basic unit at which 

the water balance has 
been set (water body, 
catchment, other) 

The  Guadiana  River  Basin  (GRB)  is  one  of  the  larger  river  basins  in  the  Iberian 
Peninsula,  being  67,147  km2,  shared  by  Spain  and Portugal  (55,527  km2  (83%)  and 
11,620  km2  (17%)  respectively).  GRB  has  been  covered  in  full  in  GuaSEEAW+ 
project. 

GRB has been separated, according Guadiana water managers’ needs, in the following 
four subareas: 

i.  Upper  Guadiana:  including  the  Oriental  Exploitation  System,  which  includes  the 

Upper Subsystem, the Bullaque Subsystem and the Tirteafuera Subsystem. 

ii.  Middle Guadiana: including the Central System and the Ardila System. 

iii.  Lower Guadiana: including the South System. 

iv.  Portugal: including the Portuguese part of the basin. 

Temporal scales 

  Time unit at which 
the water balance is 
developed  
Smallest time unit 
considered 

 

Guadiana River Basin 

Among  the  hydrological  restrictions  of  the  Guadiana  River  Basin,  the  seasonal 
irregularity  and  the  hydrological  diversity  are  the  most  remarkable  elements  (see 
figure).  As  a  result,  water  management  is  closely  connected  to  spatial  and  temporal 
considerations.  

To access climatic variability it is necessary to deal with relatively large time series up 
to 40 years long, that ensure adequate cover of the inter annual variability. 

Moreover, the seasonal variability needs a sufficiently smooth discretization in order to 
identify local and seasonal issues of lack of water availability.  

Following  the  Spanish  legislation,  a  monthly  discretization  was  established.  This 
temporal subdivision is adequate for planning, to identify local and temporal issues of 
water availability.  

Monthly  distribution  of  the  average  water  input  and  series  of  average  annual  water 
inputs of Guadiana’s river basin for the 1940-2005 period (Guadiana Hydrological Plan 
2009-2015) 

108 

 
 
 
Accounting 
environmental demand 

for 

the 

Water  accounts  in  SEEAW  describe  the  economic  activities  and  sectors  as  driving 
forces  related  to  the  water  system.  These  driving  forces  exert  different  types  of 
pressures such as water extraction and emissions to environment.  As a result, SEEAW 
does  not  consider  specifically  the  environmental  water  demand.  However,  the  water 
balance  in  the  GuaSEEAW  Project  +  (following  the  Spanish  methodology  for  the 
development  of  RBMP-River  Basin  Management  Plan)  has  taken  into  account  the 
environmental demands of the basin. 

The  environmental  demands  are  considered  as  a  restriction  pertaining  to  the  natural 
resource, external to the water use system, and have a prior and superior character.  

In  this  sense,  the  methodology  applied  clearly  identifies  the  concepts  of  natural 
resource, potential resource and available resource (see figure). These restrictions limit 
the  real  water  use:  one  can  consider  supply  or  availability  of  resources,  only  after 
having complied with these environmental constraints. 

In  addition  to  these  environmental  constraints  that  determine  the  potential  resource, 
there  are  others  of  a  technical  character  that  may  limit  water  use  (depending  on 
transport  and  storage  infrastructure,  etc.)  and  determine  the  amount  of  resources 
actually available for productive use. 

A conceptual scheme of mobilization of natural resources and their transformation into 
available  resources  (White  Paper  on  Water  in  Spain,  MAGRAMA  2000)  is  given 
below. 

The  determination of  the  amount  of  environmental  demand  is  a  complex  issue  which 
has recently been addressed in the EC Guidance document on Ecological flows in the 
Implementation  of  the  Water  Framework  Directive  (EC  2015).  In  the  work  of  the 
RBMP  of  Spanish  part  of  the  Guadiana  this  is  resolved  by  habitat  models  (Instream 
Flow Incremental Methodology) and habitat-hydraulic models. After estimating, these 
Eflows  are  introduced  in  the  model  basin  management  (AQUATOOL)  through 
appropriate  operating  rules  for  environmental  flows  met  in  strategic  surfaces  water 
bodies. 

In  the  case  of  groundwater  bodies,  the  IPH  sets  the  environmental  constraint  as  the 
average annual rate of flow required to achieve the objectives of ecological quality in 
associated surface water bodies. 

Currently, given the great difficulty to make a reliable technical approach, it has been 
considered,  as  a  first  approximation,  an  environmental  demand  as  20%  of  the natural 
resource of each groundwater body. This volume of water does not enter the calculation 
of resource available for productive purposes. 

Accounting 
desalination 

for 

potential 

In the Guadiana demarcation there is no plan to install any desalination facility, so this 
kind of actions have not been considered in the project.    

Accounting  for  potential  water 
transfers 

Water  transfers  from  other  basins  have  been  included  in  the  Hydrological  Plan  to 
increase available resources and meet existing demands on those management systems 

109 

 
that, exclusively with resources of internal origin, are unable to meet this objective. For 
this aim it is planned to import 71 Mm3/year from other river basins, which would mean 
1.5% of the available resources in the Guadiana, mostly from the Tagus. 

To carry out these transfers it is  planned to use transport infrastructures,  i.e. the Tajo-
Segura transfer. 

These  infrastructures  are  considered  in  the  Hydrological  Plan  in  modelling  future 
scenarios  of  balances.  However,  in  the  model  developed  for  the  Guaseeaw+  project 
update  exercise  was  carried  out  on  real  data  as  of  2011,  so  they  were  not  taken  into 
account as infrastructures for subsequent planning scenarios. 

All  data  used  to  develop  water  balances  are  obtained  from  the  RBMP  of  the 
international Guadiana river basin. The origin of the data and acquisition strategies are 
summarized in the following figure. 

Information mobilised 

Most of the information on water resources comes from monitoring networks: climate 
data, rivers flow rate, reservoirs water volumes, groundwater levels in aquifers. 

Data on water use comes from monitoring networks (flowmeters or gauging stations in 
irrigation  channels)  on  the  main  water  users  of  the  basin,  supplemented  by  indirect 
estimates when no direct data are available. The non-consumptive, hydroelectric power 
water  use  is  one  of  the  most  important  in  relation  to  water  volume  used.  The 
information on the volume of turbinated water is supplied by the users. In the case of 
consumptive uses, returns are calculated from coefficients that have been evaluated for 
each unit of demand depending on their specific features (or, if available, with real data 
from flowmeters or gauging stations for urban or industrial). 

Other variables are complex to estimate, especially those having to  do with exchange 
rates between different components of the water cycle: evapotranspiration, groundwater 
recharge, or transfers between rivers and aquifers or between wetlands and aquifers. To 
estimate these variables, hydrological modelling tools have been used. 

All this information has been prepared and verified under the RBMP, so homogenized 
series are arranged on a monthly basis and for a time series of 1980/81 - 2011/12. 

SEEAW  water  balances  involve  several  resources  of  several  magnitudes  that  require 
different  gathering  strategies,  which  can  cause  a  problem  when  closing  the  water 
balance  for  the  control period.  For  instance,  while  the total  water  extraction  from  the 
basin  accounts  for  about  3,000  cubic  Mm/year,  the  evapotranspiration  reaches  values 

110 

Main sources of uncertainty 

 
greater  than  14,000  cubic  Mm/year.  Such  magnitudes  exceed  in  amount  the  closing 
stocks of the water account, to which they transmit an error that almost for sure exceeds 
the value of key aspects such as water abstraction.  

The uncertainty of data such as river flows, or water abstraction is relatively small and 
known, since  most of them are  gathered from direct  measuring using devices such as 
gauging  stations  or  flow  meters.  Nevertheless,  evapotranspiration  or  soil  humidity 
(among others) are variables of  difficult estimation that required to be modelled. It is 
hard  to  calculate  the  uncertainty  of  such  variables  statistically.  There  can  be  an 
approximation through complex  sensitivity  analysis of the  model, but technically it  is 
very hard to determine its contribution to the aggregated error in the closing balance. 

With  the  available  information  it  is  possible  to  have  a  quantitative  valuation  of  the 
groundwater  transferences  between  rivers  and  aquifers.  However,  the  assessment  of 
deep groundwater reserves has a great associated uncertainty. This is mainly due to the 
complexity  of  getting 
their 
hydrodynamic properties. 

the  deep  aquifers  geometry  and 

information  on 

Link to modelling 

The balances in lakes and wetlands in the basin also have great uncertainty due mainly 
to the lack of gauging data from the official control networks.  However, this is a very 
small  volume  considering  the  global  basin  water  balance.  Besides,  the  most  relevant 
wetlands  of  the  basin  are  subject  to  environmental  protection  measures,  and  are  not 
considered as available water resources to be exploited. 

In relation to the demands, the most important of the basin are controlled by  metering 
and gauging devices in channels, so that  there is adequate approximation to the actual 
consumption of the basin. 

However,  there  are  illegal  withdrawals,  mainly  from  groundwater  in  the  middle  and 
upper  reaches  of  the  watershed  that  are  outside  of  this  type  of  direct  control.  Actual 
consumption  in  this  case  cannot  be  estimated  only  by  direct  measurements.  In  these 
areas the estimation of actual areas of irrigation and water consumed by remote sensing 
has proved to be an efficient tool. 

The  Guadiana  basin  forms  a  complex  water  resource  system,  with  several  water 
reservoirs, piping, superficial and groundwater extractions to supply agricultural, urban 
and industrial demands, flood control systems, hydroelectric production, etc. Thus, the 
main  rivers  of  the  watershed  show  a  hydric  regime  very  modified  when  compared  to 
their  natural  flow  regime.  This,  added  to  its  sharp  seasonal  variability  and  its 
remarkable  spatial  diversity,  results  in  a  very  complex  hydrological  behaviour  of  the 
basin.  

To  analyse  this  complexity,  Spanish  authorities  have  used,  in  the  scope  of  RBMP,  
hydrological  modelling  tools  to  address  hydrological  balances,  detailed  on  a  monthly 
basis and by river segment (coherent with the water bodies division considered in the 
WFD).  This  modelling  strategy  was  established  at  the  national  level  through  the 
Hydrological Planning Instruction (ORDEN ARM/2656/2008, 10th September) for all 
the basin plans shared by several Autonomous Communities. 

Schematic  diagram  of  hydrological  modelling  implemented  in  the  Guadiana  Water 
Management Plan 

111 

 
 
Water balance components in SIMPA 

Hydraulic  diagram  of  the  basin  used  in 
AQUATOOL 

This  includes  a  first  step  in  which  a  rainfall/runoff  model  (SIMPA)  was  run,  which 
allowed  assessment  of  the  water  resources  of  the  basin  in  natural  flow  regime.  After 
that,  the  results  of  SIMPA  model  were  implemented  in  a  river  basin  management 
model (AQUATOOL). The  model includes water demands for different activities and 
their returns to the rivers, the facilities for water storage and transport and the rules of 
operation of reservoirs. This modelling simulates the actual hydrological conditions of 
the  basin  and  allows  the  evaluation  of  different  stress  scenarios  (changes  in  demand, 
rules operations, etc.). It also runs on a monthly basis. 

From this modelling strategy it is possible to get a monthly water balance for series of 
up  to  40  years.  Most  of  the  data  required  by  the  SEEAW  for  water  balance  can  be 
obtained from this modelling scheme. 

The  SEEAW  tables  containing  information  on  water  balances  are  essentially  the 
physical use and supply tables, the asset account table and the matrix of flows between 
water resources. Part of the physical information of these tables feeds the hybrid tables, 
along with other physical and monetary information. 

Information  on  use  and  physical  supply  -  abstractions  and  returns  -  comes  from  the 
modelling of river basin management with AQUATOOL. Data about the water balance 
in  reservoirs  (stocks,  evaporation,  and  releases  spillway  outflows)  and  river  flows,  as 
required  in  the  table  of  asset  accounts,  have  been  taken  from  management  modelling 
with  AQUATOOL.  This  information  is  quite  consistent  and  heavily  relies  on  direct 
observation and studies of characterization of  water use and produces a picture about 
water exploitation of the basin pretty close to reality. 

The  natural  flow  regime  modelling  (SIMPA)  provides  data  on  precipitation, 
evapotranspiration,  surface  and  groundwater  runoff  and  soil  moisture.  Fundamentally 
this information nourishes the matrix of flows between water resources. It also covers 
part of the required data in the table of asset accounts. 

112 

 
 
 
 
Socio-economic 
estimated 

indicators 

Economic  information  has  been  implemented  into  GuaSEEAW+,  following  the 
implementation of SEEAW tables.  

Main  management  scenarios 
investigated 

Other  specific  challenges  met 
when  developing 
the  water 
balance 

Standard tables: 

  Physical supply and use of water. 
  Hybrid supply and use of water. 
  Hybrid account for supply and use of water. 
  Government accounts. 
  National expenditure accounts. 
  Asset accounts. 

Supplementary tables: 

  Matrix of flows between water resources. 

These  tables  have  been  incorporated  into  the  GuaSEEAW+  Data  Model  so  they 
become  dynamic  tables  that  can  be  easily  updated,  improving  their  utility  for  water 
managers  and  facilitating  the  calculation  of  results  at  different  spatial  and  temporal 
resolutions  and  the  implementation  of  indicators  supporting  policies  and  decision 
making processes: www.seeawater.eu 

The scope of the project has been implementing SEEAW tables  on the water balance 
and the hybrid tables with real data (updated 2011). In this sense, it only has taken into 
account the current management scenario as it is implemented in the RBMP. No other 
scenarios have been simulated.  

Considering the most relevant tables in the water balance, the use and physical offer, is 
possible  to  get  a  suitable  outcome  from  the  available  information.  The  results  are 
consistent with the physical reality of the basin since they are  largely based on direct 
observed real data. Besides, these balances generated by the responsible authorities are 
consistent  with  the  official  figures  used  in  the  RBMP  for  the  allocation  of  water 
resources and in the measures of the Plan. 

The assets tables and matrix of  flows between  water resources complement the water 
balance  vision  in  SEEAW.  There  are  some  minor  gaps  in  these  tables,  especially 
related to water stored in lakes and wetlands, for which there is almost no information 
coming  from  control networks.  However, this is a very small  volume  considering the 
global basin water balance. Besides, the most relevant wetlands of the basin are subject 
to  environmental  protection  measures,  and  are  not  considered  as  available  water 
resources to be exploited. 

The  basin  deep  groundwater  reserves  are  another  source  of  uncertainty.  With  the 
available  information  is  possible  to  have  an  objective  quantitative  valuation  of  the 
groundwater  transferences  towards/from  the  rivers.  However,  the  assessment  of  the 
deep groundwater reserves has a great associated uncertainty. 

General comments  

The Spanish Water authority has shown a great interest by the applicability of statistical 
SEEAW methodology for water planning in Spain. 

The Spanish water authorities already have a well-established background in the field 
of  water  balances  necessary  to  address  recurrent  episodes  of  scarcity  in  many  of  the 
Spanish basins. RBMP in Spain are demanding consistent water balances, since from it 
depends  the  significant  investment  in  water  infrastructure  to  be  undertaken  by  the 
authorities in Spain through the programmes of measures in the respective management 

113 

plans. 

Therefore,  and  in  line  with  the  guidelines  of  cost  recovery  policy,  one  of  the  main 
concerns  of  the  authorities  is  the  need  to  establish  relationships  between  water  and 
economy at the administrative level in order to define, promote and discuss important 
decisions.  It  seems  that  SEEAW  tables  will  help  to  achieve  it.  Its  mandatory 
disaggregation between economic sectors, dry and irrigated agriculture, (between blue 
and green water, as stated in water footprint terms), types of industries and taking into 
account tourism is quite important. They consider mandatory to know the correct price 
of water in order to better define a proper recovery cost policy. 

Presently  it  is  remarkably  difficult  to  establish  relationships  between  hydrologic  and 
economic data, as they are compiled by different authorities with different spatial and 
temporal aggregation levels, standards and objectives.  

114 

 
 
Name of the Pilot project 

Water Accounting in a Multi Catchment District (WAMCD) 

Spatial scales 
 

Territory (catchment, other) 
covered by the pilot project 

  Basic unit at which the water 

balance has been set (water 
body, catchment, other) 

The  methodological  approach  is  focused  on  filling  the  SEEAW  tables  for  the 
Mediterranean  Basins of  Andalucía  River  Basin  District [MBA  RBD].  The  total 
surface  area  is  17,762.32  km2.  The  RBD  includes  16  subsystems,  ranging  from 
145.8 km2 to 3,481.02 km2. 

Water  balances  have  been  set  at  subsystem  level  (assets  account)  or  RBD  level 
(physical supply and use), but rely on subsystem datasets. 

The choice is justified by the wide range of climatic conditions and management 
differences among subsystems. The Project was intending to provide a benchmark 
for the application of water accounts to heterogeneous environments and climates, 
but with similar datasets and criteria. 
As  far  as  water  balances  are  concerned  (SEEAW  water  assets  tables),  the  time 
unit has been the month. 

The main hydrological datasets are available on a monthly basis and a variety of 
modelling tools (integrated in AQUATOOL  DSS)  have been applied  working at 
this scale (see below). The  monthly scale better reflects the seasonal irregularity 
of water regimes in the RBD. 

Another important issue is the reference period. There are two basic options when 
calculating water balances: using one specific (hydrological) reference  year (e.g. 
2005/06) or using some statistical value representing a series of years. According 
to  the  Spanish  Technical  Regulation,  balance  between  resources  and  demands 
must  be  representative  of  normal  supply  conditions.  This  criterion  has  been 
reproduced by using the  50th percentile of the  monthly components of the  water 
assets. 

The  analysis  of  the  irregularity  of  the  hydrological  regime  has  been  introduced 
through  a  complementary  assessment  to  determine  asset  accounts  for  the  driest 
phase of the reference period, namely the triennium from 1992/93 to 1994/95. 
A  specific  tool  for  environmental  allocation  assessment  (CAUDECO)  has  been 
tested.  E-flow  regimes,  determined  in  the  framework  of  the  River  Basin 
Management  Plan  [RBMP],  have  also  been  considered  when  simulating  the 
exploitation of systems depending on reservoirs. Nevertheless, SEEAW does not 
explicitly consider environmental demands. 
Both  "transfers  from  and  to  the  rest  of  the  world"  and  "desalinated  water"  (two 
expressions from the SEEAW tables) are specifically accounted for in the Table 
III.3  of  SEEAW  (Detailed  physical  supply  and  use  tables).  In  the  Table  VI.1 
(Asset  accounts)  the  inflows  from  both  desalination  and  external  transfers  have 
been allocated, for practical reasons, under the concept  Transfers from upstream 
territories. 
In addition, internal transfers within the RBD have been considered when filling 
the tables. 

Temporal scales 

 

 

Time unit at which the water 
balance is developed  
Smallest time unit considered 

Accounting 
demand 

for 

the  environmental 

Accounting for potential desalination 

Accounting for potential water transfers 

115 

 
 
 
 
 
 
 
Information mobilised 

Main sources of uncertainty 

Potential data sources have been identified and available data have been collected, 
mainly from: 
 

”Mediterranean Basins of Andalusia River Basin Management Plan 2009" 
[RBMP-09] and the “Draft Proposal of Mediterranean Basins of Andalusia 
River Basin Management Plan 2015" [RBMP-15] 
SIMPA model (hydrological datasets) 
Institute of Statistics and Cartography of Andalusia 
Spanish Statistical Office 

 
 
 

The information collected has been put into relation with the data included in the 
RBMPs and with the grouping of ISIC activities required by SEEAW. 
The  combination  of  information  from  different  sources  causes  certain  problems 
for  closing  water  assets  balances.  Ideally,  the  use  of  consistent  rainfall-runoff 
models  integrated  with  management  simulation  models  should  end  up  in 
completely coherent water assets.  

This  approach  has  been  explored  in  the  WAMCD  Project  and  should  be 
implemented  in  the  framework  of  the  next  WFD  management  cycle.  In  the 
meantime,  the  component  Other  changes  in  volume  of  Table  V-1  that  has  been 
calculated as a residual, gives a relative magnitude of the maladjustments caused 
by  mixing  different  sources.  This  way,  it  is  relevant  to  focus  future  efforts  on 
those subsystems were major problems have been identified. 
Direct measurement (or fine assessment) of stocks of groundwater and soil water 
are not feasible at reasonable costs for the whole RBD. 

EVALHID  and  CAUDECO  modules  from  AQUATOOL  DSS  have  been  tested 
and  a  specific  tool  for  data  transfer  from  this  model  to  the  SEEAW  tables  has 
been applied in the case study of the Velez River Basin, where both rainfall-runoff 
and simulation management models were available. 

116 

 
 
 
 
 
Link to modelling 

EVALHID  in  combination  with  SIMGES  has  proven  to  be  an  effective  tool  for 
organizing the required information since: 
 

It allows choice among different rainfall-runoff models (Témez, HBV, 
Sacramento and others), to be selected depending on the available data, the 
complexity of the basin and the user’s experience. 
It provides spatially distributed information on the hydrological parameters 
needed for a comprehensive assessment: temperature, precipitation, potential 
actual evapotranspiration, infiltration, surface runoff, groundwater runoff, 
soil storage. 
Streamflow series may be introduced in management simulation models 
(such as SIMGES), so it is possible to obtain other relevant data regarding 
water allocation: development of storage in reservoirs, supply deficits, 
environmental flows, water transfers, outflows to the sea...Moreover, the 
results of SIMGES reflecting the altered flow regime may feedback into the 
calibration of the rainfall-runoff model. 

 

 

Socio-economic indicators estimated 

We  understand  that  these  kind  of  models  are  fundamental  for  supporting 
management decisions for a variety of reasons: 
  They introduce seasonal and inter-annual variability, which are key aspects 
when hydrological variability and water scarcity are relevant issues. 

  They allow simulation of different management alternatives/solutions, both at 

detailed or strategic planning level. 

  They enable a better assessment of scenarios linked to expected changes in 

pressures or climate induced ones: on the one hand, by translating 
temperature and precipitation variations into effects in the other components 
of the water cycle (streamflow, infiltration…); on the other hand, helping to 
evaluate their impacts on water allocation to human activity and the 
environment. 

On the one hand, SEEAW includes a set of hybrid accounting tables to integrate 
physical and economic datasets with water use accounts. 

On the other hand, to synthesize the massive amount of information compiled, a 
collection of thirty-five relevant indicators has been calculated on the basis of the 
SEEAW tables (and with the occasional support of intermediate/auxiliary tables). 
Indicators  refer  to  water  resource  availability,  water  use  for  human  activities, 
opportunities to increase effective water supply, water cost, pricing and incentives 
for conservation and other supplementary indicators. 

Additionally, comprehensive WEI+ estimates have been made. 

117 

 
 
 
Main 
investigated 

management 

scenarios 

Other  specific  challenges  met  when 
developing the water balance 

The  whole  work  has  been  closely  linked  to  the  RBM  planning  process  and  is 
intended to be consistent with RBMP-15 and, at the same time, provide valuable 
inputs  to  the  planning  process.  Three  scenarios  have  been  characterized  by  the 
SEEAW set of tables: 2009 (baseline, corresponding to RBMP-09), 2015 (current 
scenario of RBMP-15) and 2021 (future scenario after the implementation of the 
PoM). 

All the measures included in the MBA PoM and others suggested by the Project 
Team  have  being  structured  and  classified.  Moreover,  the  resulting  group  of 
measures/lines of action (along with the main drivers) have been characterized in 
terms of their main effects on the water accounts, and summarized in a catalogue. 
For each entry, the following data are included: name of the measure; response to; 
main effects on physical accounts; main effects on economic and hybrid accounts; 
supplier and user; metering; assessment; PoM (inclusion or not in the MBA PoM); 
additional  information  (including  relevant  regulatory  or  administrative  tools 
supporting the measure). 
The main challenges identified were (some have been mentioned before): 
  Complex calculation of physical tables when mixing data from different 
information sources, eroding internal consistency of water assets. 
  Lack of data on volume, quality and destination of water returns to the 

environment after use.  

  Lack of direct measurement of groundwater reserves, soil water and scarce 

data on the snowpack. 

  Different alternatives for the calculation period for water assets. 
  Consideration of hydrological irregularity. 
  Environmental water allocation not properly considered in SEEAW. 
 

SEEAW provides a great deal of data, difficult to handle and to extract 
conclusions. 
Scale of available economic information corresponds to the administrative 
units, not water catchments. 

 

  Aggregation of ISIC activity sectors, relevant for SEEAW in the 

Input/Output Tables and other macroeconomic datasets. 

Different solutions have been adopted to overcome these problems, as reflected in 
the upcoming Final Technical Report. 

118 

 
 
General comments  

Regarding potential use: 
  The SEEAW provides a useful standard for the building of water balances 
and a conceptual framework to integrate economic data, describing the 
interaction of economic activity, water resources and water use. 
If sustained over time, the SEEAW can be a useful tool for monitoring the 
evolution and impacts of policies related to water. 

 

  The SEEAW is compatible (and may be complementary) with the traditional 
water balances established in the Spanish RBMPs for the allocation and 
reserve of water resources. 

  The calculation of the cost recovery rate, as required by the Water 

Framework Directive, may be enhanced with the support of the SEEAW, 
since interchanges among activities related to the provision and use of water 
are further clarified. 

  The SEEAW may be a support tool to analyse the effects of strategic options 

affecting the water cycle and water use. 

Regarding limitations: 
 

It is difficult to ensure internal consistency of water assets when direct data 
and model (and/or other kind of) estimates are used, which is the usual case. 
Direct measurement (or fine assessment) of stocks of groundwater and soil 
water are not feasible at reasonable costs for the whole RBDs. 

  The SEEAW is very demanding in terms of information requirements and, 
frequently, no direct data are available to fill many of the boxes. In Spain, 
this is particularly true in the case of economic statistics, forcing the use of 
additional criteria and proxies. The lack of information hinders practical 
applicability of the SEEAW and questions the uniformity and comparability 
of results, eroding, to some extent, its positive role as a common standard. 

  Though SEEAW provides useful information on the pressure exerted by 

human activity on water ecosystems, environmental water allocation is not 
integrated into SEEAW and additional analyses and indicators have to be 
developed and carried out. 

  The SEEAW cannot substitute DSS tools (AQUATOOL or similar) to build 
significant water balances, if water scarcity and hydrological irregularity are 
a major issue. Similarly, it is not the appropriate tool to analyse specific 
investment options where environmental and socio-economic impacts and 
benefits must be carefully assessed. 

119 

 
 
 
 
ANNEX III  –COMPARISON BETWEEN THE “SEEAW ASSET ACCOUNTS” AND THE “WATER 
BALANCE” COMPONENTS  

The System of Environmental-Economic Accounting for Water (SEEAW) was developed by 
the  United  Nations  Statistics  Division  (UNSD)  in  collaboration  with  the  London  Group  on 
Environmental  Accounting  and  contributions  from  the  Eurostat  Task  Force  on  Water 
Accounts, with the objective of standardizing concepts and methods in water accounting. The 
SEEAW  purpose  is  to  encourage  countries  to  launch  an  integrated  water  resources 
management  (IWRM)  approach through the  establishment of an operational  framework that 
integrates  economic  and  hydrological  information.  Following  the  original  Handbook  of 
National  Accounting  “Integrated  Environmental  and  Economic  Accounting  -200341” 
(commonly  referred  to  as  SEEA-2003)  which  provided  the  opportunity  to  develop 
methodologies  for  water  accounts,  the  UN  Committee  of  Experts  on  Environmental-
Economic Accounting (UNCEEA) was established in 2005 with an aim to raise the system of 
environmental  accounts  to  an  international  statistical  standard  and  to  advance  the 
implementation  of SEEA in  all countries. The  final draft of the SEEAW  was  established in 
2007  to  conform  to  the  content  and  style  of  an  international  statistical  standard,  while  a 
fictitious  dataset  was  developed  to  populate  the  standard  tables  (UNSD,  200742),  and  was 
further  updated  in  2012  [9].  The  main  argument  for  implementing  the  SEEAW  is  that  it 
provides the much-needed conceptual framework for organizing  hydrological  and economic 
information  in  support  of  Integrated  Water  Resource  Management  (IWRM),  permitting  a 
consistent analysis of the contribution of water to the economy and the impact of the economy 
on  water  resources,  and  should  be  thus  adopted  as  the  international  standard  for  water 
statistics. The SEEAW-2012 accounting framework considers the stocks, flows and exchange 
of flows  between the environment (i.e. water  resources  and the different  components of the 
hydrological  cycle)  and  the  economy  (i.e.  water  abstraction,  use  and  return  from/to  the 
different  NACE  economic  activities),  and  includes,  as  part  of  its  standard  presentation, 
information on the following [9]:  
  Stocks and flows of water resources within the environment; 
  Pressures  imposed  on  the  environment  by  the  economy  from  water  abstraction  and 
emissions  added  to  wastewater  and  released  into  the  environment  or  removed  from 
wastewater; 

  The supply of water and its use as an input in production processes and by households; 
  The reuse of water within the economy; 
  The  costs  of  collection,  purification,  distribution  and  treatment  of  water,  as  well  as  the 

service charges paid by its users; 

  The  financing  of  these  costs,  that  is,  who  is  to  pay  for  the  water  supply  and  sanitation 

services; 

41United  Nations  Statistics  Division  (UNSD).  2003.  Handbook  of  National  Accounting:  Integrated 
Environmental  and  Economic  Accounting:  An  Operational  Manual,  Series  F,  No.  78,  Rev.1  (United  Nations 
publication, Sales No. E.00. XVII.17). 
42United Nations Statistics Division (UNSD). 2007. System of Environmental-Economic Accounting for Water. 
Final Draft, March 2007.   

120 

 
 
                                                 
 
  The payment of permits for access to abstract water or to discharge wastewater; 
  The  hydraulic  stock  in  place,  as  well  as  investments  in  hydraulic  infrastructure  made 

during the accounting period. 

SEEAW also presents water quality accounts (yet at an experimental level) and proposes a set 
of indicators which can be derived from the accounting systems (rather than from individual 
sets of water statistics) and are useful to the policy makers. 

The five main categories of water accounts are described below [9]:  
1.  Physical supply and use tables and emission accounts: the physical supply and use tables 
collect information on the volumes of water exchanged between the environment and the 
economy  (abstractions  and  returns)  and  within  the  economy  (supply  and  use  within  the 
economy).  The  emission  tables  collect  information  on  the  quantity  of  pollutants  which 
have been added to or removed from the water (by treatment processes) during its use by 
economic activities and households. 

2.  Hybrid  and  economic  accounts:  these  accounts  combine  the  physical  information  of  the 
water supply and use tables with monetary information (e.g. costs associated with water 
use and supply, such as water abstraction, purification, distribution, wastewater treatment, 
etc.).  They  also  provide  information  on  financing,  i.e.  the  amount  that  users  pay  for  the 
services of wastewater treatment, etc. 

3.  Asset accounts:  these tables provide information on the water resources in physical terms 
(opening  and  closing  stocks,  changes  in  stocks  due  to  precipitation,  evapotranspiration, 
inflows, outflows, abstractions and returns) and link water availability to abstractions, thus 
facilitating 
the  environment.  The  additional 
supplementary tables  convey information on the flows between the compartments of the 
hydrological cycle. 

identification  of  pressures  on 

the 

4.  Quality accounts: these tables provide information on the quality of the stock of the water 

resources. They are still at an experimental level. 

5.  Valuation of water resources: these tables provide information on the valuation of water 
and water resources. In the case of water quality these are still at an experimental level. 

121 

 
 
 
Figure 1: SEEAW “Asset Accounts main” and supplementary tables. 

122 

 
 
 
Figure  2:  Main  water  flows  between  the  inland  water  resource  system  and  the  economy 
captured by the SEEAW. Source: UNSD, 2012 

123 

 
 
 
Table 1. Comparison between SEEAW Asset Accounts and Water Balances parameters and definitions 

SEEAW Parameter 

SEEAW Definition 

WB Parameter 

WB Definition 

Precipitation (in artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, soil water) 

The total volume of atmospheric wet precipitation, such 
as rain, snow and hail, on a territory in a given period 
of time. 

Precipitation (areal, in 
the hydrological unit of 
analysis) 

Total volume of atmospheric wet precipitation (rain, snow, hail, 
etc.). Precipitation is usually measured by meteorological or 
hydrological institutes. 

Inflows from upstream 
territories (in artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, groundwater) 

Inflows: Water that flows into a stream, lake, reservoir, 
container, basin, aquifer system, etc. It includes inflows 
from other territories/ countries and inflows from other 
resources within the territory. 

External Inflow (to 
surface water, 
groundwater) 

Inflows from other resources in 
the territory (in artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, groundwater, 
soil water) 

S
T
U
P
N
I

Incorporated in 
Returned water 

Returns (to artificial reservoirs, 
lakes, rivers, snow/ice/glaciers, 
groundwater, soil water) 

Water that is returned into the environment by an 
economic unit during a given period of time after use. 
Returns can be classified according to the receiving 
media (water resources and sea water) and to the type 
of water, such as treated water and cooling water). 

Returned water  

Total volume of actual flow of rivers and groundwater entering 
the hydrological unit of analysis from neighbouring territories/ 
other units [hm3/ time unit]. External Inflow must not be 
confused with the inputs received from economic units (e.g. 
desalination, water reuse) or the imported water since those are 
directed for consumption and only a part of them is finally 
discharged to the rivers and groundwater via returns. 

Internal transfers in the hydrological unit such as artificial 
groundwater recharge with source-water generated within 
(abstracted from) the hydrological unit, and/or recharges into 
rivers with source-water generated within (abstracted from) the 
hydrological unit can be considered under the returned water 
component for the current Water Balance calculation purposes. 
Discharges to the sea are excluded. 

Volume of abstracted water, and/or water produced by economic 
units, and/or imported, that is discharged to the fresh water 
resources of the hydrological unit either before use (as losses) 
or after use (as treated or non-treated effluent). It includes 
water that was directly discharged from a user (e.g. domestic, 
industrial etc. including cooling water, mining), and water lost 
from the waste water collection system (as overflow or leakage).  
* Internal transfers in the hydrological unit such as artificial 
groundwater recharge with source-water generated within 
(abstracted from) the hydrological unit, and/or recharges into 
rivers with source-water generated within (abstracted from) the 
hydrological unit can be considered under the returned water 
component for the current WB calculation purposes. Discharges 
to the sea are excluded. 

124 

 
 
Evaporation/ Actual 
Evapotranspiration (from 
artificial reservoirs, lakes, 
rivers, snow/ice/glaciers, soil 
water) 

Evaporation: The quantity of water transferred from the 
soil to the atmosphere by evaporation and plant 
transpiration. 

Actual 
Evapotranspiration (s: 
surface, i: interception, 
t: transpiration)   

Actual Evapotranspiration: The amount of water that 
evaporates from the land surface and is transpired by 
the existing vegetation/plants when the ground is at its 
natural level of moisture content, which is determined 
by precipitation. 

Total volume of evaporation from the ground, wetlands and 
natural water bodies and transpiration of plants. According to the 
definition of this concept in hydrology, the evapotranspiration 
generated by all human interventions is excluded, except rainfed 
agriculture and forestry. The “actual evapotranspiration” is 
measured or calculated using different types of mathematical 
models, ranging from very simple algorithms (Turc, Penmann, 
Budyko, Turn Pyke, etc.) and corrections related to vegetal cover 
and season to schemes that capture the hydrological cycle in 
detail. 

Outflows to downstream 
territories (from rivers, 
snow/ice/glaciers, groundwater) 

Outflows to the sea (from 
rivers, snow/ice/glaciers, 
groundwater) 

Outflows to other resources in 
the territory (from rivers, 
snow/ice/glaciers, groundwater) 

S
T
U
P
T
U
O

Abstraction (from artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, groundwater, 
soil water) 

A
H
C

E
G
N

Opening Stocks (in artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, groundwater, 

S

Flow of water out of a stream, lake, reservoir, 
container, basin, aquifer system, etc. It includes 
outflows to other territories/countries, to the sea and to 
other resources within the territory. 

Outflow (from surface 
waters, from 
groundwater) 

The total volume of actual outflow of rivers and groundwater into 
the sea plus actual outflow into neighbouring territories (outside 
the hydrological unit of analysis). Note: Environmental Flow-EF 
and other Water Requirements-WR as defined e.g. by treaties are 
a part of the Outflow. 

Incorporated in 
Abstraction 

Abstraction (from 
surface water, 
groundwater) 

Internal transfers in the hydrological unit such as artificial 
groundwater recharge with source-water generated within 
(abstracted from) the hydrological unit, and/or recharges into 
rivers with source-water generated within (abstracted from) the 
hydrological unit can be considered under the returned water 
component for the current calculation purposes. Discharges to the 
sea are excluded. 

Water removed from surface or groundwater resources, either 
permanently or temporarily, regardless of any input from water 
return or artificial recharge. Mine water and drainage water are 
included. Water abstracted for hydropower generation (in-situ 
use) should be excluded from the formulation of the water 
balance equation, while water abstracted for cooling should be 
included. Water abstractions from groundwater resources in any 
given time period are defined as total amount withdrawn from the 
aquifer. 

The amount of water that is removed from any source, 
either permanently or temporarily, in a given period of 
time for final consumption and production activities. 
Water used for hydroelectric power generation is also 
considered to be abstraction. Total water abstraction 
can be broken down according to the type of source, 
such as water resources and other sources, and the type 
of use. 

Stocks at the beginning of the accounting period. 

125 

 
 
 
 
 
 
soil water) 

Other changes in volume (in 
artificial reservoirs, lakes, 
rivers, snow/ice/glaciers, 
groundwater, soil water) 

Closing stocks (in artificial 
reservoirs, lakes, rivers, 
snow/ice/glaciers, groundwater, 
soil water) 

Stocks at the end of the accounting period  

Change in Storage - 
Natural ΔSnat: in lakes, 
rivers, soil, 
groundwater, snow and 
glaciers 
- Artificial ΔSart: in 
regulated lakes, 
artificial reservoirs 

Changes in the stored amount of water ( >0, if storage is 
increasing) during the given time period, including river bed, 
lakes, underground water (soil moisture and groundwater) as 
natural part of the storage (Snat) and in regulated lakes or 
artificial reservoirs (Sart). ΔS can be ignored for long-term 
averages if it is not feasible to evaluate them, but should be 
evaluated in annual calculations and be considered in monthly 
calculations. 

126 

 
 
 
 
 
 
 
K
H
-
0
1
-
1
5
-
7
2
8
-
E
N
N

-