Head Office in NWSDB
14th DEC 2015

Tatsuya TOBE1, Koichi MATSUBARA1,Sujithra WERAGODA2,and Shameen JINADASA3
1 Nihon Suido Consultants Co., Ltd., Tokyo, Japan,
2 National Water Supply and Drainage Board, Sri Lanka,
3 Faculty of Engineering, University of Peradeniya, Sri Lanka
1Agenda• Introduction• Background and Objective– Significance of Modeling Approach– Review of a Water Safety Plan

• Methodology– Model Framework and prioritized model• Results and Discussion– Simulation Results for Present Status– Evaluation of Countermeasures• Conclusion and Recommendation
22Who We Are?

 Offering total solution for Water and Water Environment No.1 share in Japan domestic Water Supply Consultancy market
 Business experiences in over 50 countries

3Our Business FieldPlanningDesigningConstruction

OperationManagement

 Project Appraisal and evaluation
 Master Plan Feasibility Study Preliminary & Detailed Design
 Construction Supervision
 Training for Plant Operation & Maintenance Training for Technology Transfer
 Review of Existing Management Organizationand Practices
 Environmental Impact Assessment
 Water Quality Analysis & Assessment
 Pollution Control Programs
 Leakage & NRW control Programs
 Data Mapping & GIS
 Asset Management4Research Framework• Collaborative research between NSC and University ofPeradeniya for Water and Environment•JointWorkshop• MoU formulation
5Background• Emerging Water Environment Issues in Sri Lanka– Eutrophication, Agrochemicals– Water-related Diseases– Incidents by Wastewater
Pollutions– Leachate from
Waste Disposal Site
Meda-Ela Confluent, Kandy• Countermeasures to secure Safe Drinking Water– Water Safety Plan
• Unknown likelihood and Significance of Risks• Need stakeholders involvement to control
6

Background and Objective• Modeling and Simulation Approach
MeritsProblems- Prospective Approach:- Input / Verification data
Give scientific verification to policies,
are not always available
Evaluate Countermeasures- Ad-hoc, Not replicable by- Accountability:
practitioners
Show visually to explain to thepublic• Objectives– Review water resources problems from actual watersafety plan
– To establish the simulation model to evaluate the risks atwater safety under limited resource conditions
7Study Area: Mahaweli River Basin near Kandy
Greater Kandy
WTP:
72,000 m3/day(Phase II, by 2014)

Population
Served:400,000Mid-canalWSP:
formulated onJuly 2014

8Research Flow
Review of WSP
Identification of Risk Incidents
Determination of Model
Data Collection- Communication
with corresponding
authorities- Literature Review- Site Inspection- Preliminary DataCollection- Data gathering

Modeling
Output Results
9

Review of Greater Kandy Water Safety Plan (1)• “Very High” Risk Incidents focused at Source
Location /Process step
SourceSourceSourceDistribution
chamber
Servicereservoirs
Pipe
network

Hazardous event

Hazard type

Pathogenic contamination from septic
Physical/Chemical/micrtanks and waste from Kandy city throughobiological
Middle canal (Meda‐Ela)
Leachate from Kandy city garbage
Physical/Chemical/mic
dumping site entering intake
robiological
Pollution by agrochemicals during
Chemicalspraying season
Power failure at WTP

Chemical & Microbial

Unauthorized personnel entering
premises

Chemical & Microbial

Contamination of treated water

Microbial

10

Review of Greater Kandy Water Safety Plan (2)• Hazard identified at source (catchment)– WTP is near to Solid Waste Dumping Site at Gohagoda– There is some possibility for contamination from back flowof the Mahaweli River– Major concern but difficult to evaluate its significance

Gohagoda Leachate Discharge

Greater Kandy Intake

Gohagoda Dumping Site

Intake for Grater Kandy WTP
11Methods(1) : Overall Model Framework
Catchment
Reservoiror Lake①

OutputInput / Output② Mahaweli River

Polgolla Reservoir
Intake for
Grater Kandy
WTP

Hydro
Power
Intake for
Polgolla WTP③

Kandy Lake
Mid‐canal

Gohagoda
Dumping
Site
12Intake for
Kandy SouthWTP

Methods(2) : Catchment ModelRainfall* including garden & bare area
Catchment(Land-use)
ForestPaddyTea
Gardenetc.

TouristPopulation

Residential
PopulationUrban*

Non-point Source
Pollution Load

Point Source
Pollution Load

Runoff Coefficient

Runoff Coefficient

Calculate annual load

Discharged
Pollution Load

L=αQβ

COD
(ton/day)

400
200
0
1/1

2/1

3/1

4/1

5/1

6/1

7/1

8/1

9/1

10/1

11/1

12/1

13Methods(3) : Reservoir Model

Vertical two dimensional Model<Hydraulic Model><Water Quality Model>

Density flow shall be analyzed in reservoir(Horizontal)

Transfer
pollution load
according toadvection &diffusion(Vertical)

14

Methods(4) : Detail of Reservoir Model
Hydraulic Model Flow velocity in flow and vertical direction Water level (water volume)
outflow流出 Density

Infloｗ
流入

Equation for Continuity

Ｙn+1

ΔＹＹnu  v
0x yΔＸＸi
Ｘi+1

Equation for Conservation of Momentum  u   P    u    u    Ayuu u v       Ax
t x
yx    x  x  y  y P  gy(Assumption of hydrostatic pressure distribution)
15Methods(5) : Detail of Reservoir Model
Water Quality Model
Equation for Temperature Balance

TTT T   T H uv
 Kx
   K ytx
y x x  y y  C w

Equation for Ecological ModelCCC   C   C Suv
  Dx   D ytx
y x x  y y 

solar
radiation
Temperatureadvection diffusion

reaeration(only surface)DOdegradation
D-COD

degradation

consumption with degradation

P-COD
advection

advection
I-P
diffusion

IntakeIntake摂

diffusion

degradation

degradation
O-PIｰN

extinction

Phytoplankton

advection

extinction

O-N

diffusion

sediment

sediment16

Methods (5): Scoping Target Water Quality Indicators• Background Water Quality 1)– Cd (3.9-21.5 μg/L)• Heavy Metals in Leachate 2)– Cr, Fe, Ni, As, Cd, Se, Pb• Other Substances in Leachate 3)– Mn, PO43-1) Bandara et al., 2010
2) Sewanndi et al, 2012
3) Dharmarathne and Gunatilake, 2013

⇒ Pb in leachate is higher than other substances.

Pb was selected as model indicator for simulationin this study.
17

Required Input Data for Boundary Conditions
Items
Catchment Framework
River Profile
Hydrology（Precipitation/ Flow Volume）
Water Quality
Meteorology
Dimension of Dam
Operation Rule of Dam/ Barrage

This Study

Source✔
✔

Provided by Uni.

✔

Provided by Uni.

✔
✔
✔

Literature
Literature18

Topographical Condition (River Profile)

Polgolla Reservoir with total length of 7.5 km was divided into meshes atintervals of 0.5 km in flow direction and 1.0 m in vertical direction
19

Hydrological Condition

inflow (M.C.M)

50.0

Polgolla Dam (2014)

40.0
30.0
20.0
10.0
0.01/12/1 3/1

4/1

5/1

6/1

7/1

8/1

9/1 10/1 11/1 12/1

Inflow condition for Polgolla Reservoir was set according to the actual record ofinflow volume in year 2014.
Hydrological condition in 2014 corresponds to dry year in recent 7 years.

20

Meteorological Condition
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Temp(℃)

23.4 24.2 25.5 26.1 25.7 25.0 24.7 24.7 24.7 24.6 24.4 23.7

solar radiation(W/m2)

371 386 406 416 408 393 387 396 409 412 398 378

relativehumidity(%)

83.8 79.0 76.5 82.5 83.5 83.4 82.0 81.0 81.2 85.2 87.8 86.8

windspeed(m/s)

0.8

cloudamount(‐)

0.48 0.42 0.47 0.58 0.71 0.72 0.74 0.73 0.77 0.72 0.66 0.58

0.6

0.3

0.2

0.8

1.0

1.0

1.0

1.0

0.5

0.8

0.8

Meteorological Condition is required to calculate water temperature forsunshine and heat balance in water surface in reservoir
21

Water Quality Condition①Inflow from ②Inflow fromKandy Lake
Mahaweli River
Catchment
Area (km2)
Discharge
Volume (m3/s)
COD (mg/L)
T-N (mg/L)
T-P (mg/L)
Pb (mg/L)
Zn (mg/L)③Leachate from
Gohagoda Damping Site

255

1063

0.06

13.1

54.6

0.006

22.4
5.9
1.1
0.005
0.145

8.0
1.9
0.4
0.005
0.145

700
700
8.0
12.9
700

Water quality condition was set according to discharged water
quality calculated through the catchment model.
Concentration of Pb was set according to the observed data.
22Interface of Simulation Model

The Simulation Model can configure input and output data on
Microsoft Excel interface.
Users can easy to handle the simulation model (e.g. change ofinput data and evaluation of simulation results).
23

Results(1): Simulation Results for Reservoir• Water temperature; between surface and bottom layer is different due tosunshine and low flow volume especially in dry season.
24

Results(2): Simulation Results for Reservoir& Flow Velocity

Backflow

Backflow• Flow Velocity: Difference in temperature makes density flow (Fair current in
middle layer and backflow in surface and bottom layer).
25

Results(3): Simulation Results for Intake Water Quality• Backflow: Substances in Leachate could flow back toupstream by approx. 2 km due to density flow.
26

Results(4): Simulation Results for Intake Water Quality
Pb(mg/L)
0.010

Current (2014)

WHO Guideline Value
0.008
0.006

Background Value

0.004
0.002
0.000
2014/1/1

2014/2/1 2014/3/1

2014/4/1

2014/5/1

2014/6/1

2014/7/1

2014/8/1

2014/9/1 2014/10/1 2014/11/1 2014/12/1• Seasonal variation: variation exists but not significant

27

Results(5): Control Measure Identification
Case
Case 01
Case 02

Control Measure
Installation of fence in bottom layer
Raw water Intake from surface layer

Pb(mg/L)
0.010

Current (2014)

Case01

Case02

WHO Guideline Value
0.008
0.006

Background Value

0.004
0.002
0.000
2014/1/1

2014/2/1 2014/3/1

2014/4/1

2014/5/1

2014/6/1

2014/7/1

2014/8/1

Chl‐a(μg/L)
70

2014/9/1 2014/10/1 2014/11/1 2014/12/1

Current (2014)

Case01

Case02

60
50
40
30
20
100
2014/1/1

2014/2/1 2014/3/1

2014/4/1

2014/5/1

2014/6/1

2014/7/1

2014/8/1

2014/9/1 2014/10/1 2014/11/1 2014/12/1

28

Case 01:
Pb increased due toretention at bottomlayer.
Case 02:
Pb decreased, while
Chl-a increase
especially in dry
season due to growthof phytoplankton.

Results(6): Control Measure Identification
Case 01

Fence

As for Case 01, due to installation of fence, contaminatedsubstances stay longer in bottom layer at intake and intake
water quality of Pb increase.
29

Results(7): Control Measure Identification
Case 02

Intake from Surface

As for Case 02, intake water quality of Pb decrease by intake
from surface.
30

Results(8): Control Measure Identification
Case 02

As for Case 02, intake of Chl-a increase especially in dry
season due to growth of phytoplankton in surface.
31Discussion: Model Flow of Simulation Application
to WSP
Which System to be examined?
- Concern of Incidents- Significant (Population)

Screening of Target WS
Review of WSP

Communication with Local
Stakeholders

Identification of Problems
Determination of Model

Involvement of Local
Authorities

Data Collection
Modeling

Collaboration for
Data Acquisition

Output Results
Verification by Monitoring Data32

Conclusion (1)• Water Safety Plan of Greater Kandy WTP indicatedwater source issues are identified as “Very High” risk
because of unavailability of observed data.
• Water Quality Simulation model for Pollgolla Reservoir
implied that;– Leachate contamination may flow back by 2km due
to density flow*.
– As countermeasure, fences at Intake (Case 01) may
have adverse impact on water quality and Intake atsurface (Case 02) is effective
while Chl-a (phytoplankton) concern remains.
* Modeled substance (Pb) is below WHO guideline value
33

Conclusion (2)• In this research, we could not reach quantitative rerisk assessment utilizing the results because theconcentration of modelled substances (Pb) did notgo beyond the WHO guideline level.
• More research is needed for identifying the possible
harmful substances such as agro-chemicals,
carcinogenic substances and other unknownsubstances.
• Application of water quality simulation model forwater safety is effective to manage raw water quality
and figure out likelihood and significance of risks forincidents.
34

Recommendations• Utilize simulation approach for public
communication and policy making– Visualization for communicating with stakeholders– Acceleration for Proactive Measures• Establish replicable simulation models/workflows
considering limited resources– Data Availability is the Key Factor– Improvement of usability is necessary• Monitoring– Data Collection and Communication among institutions– Find Feasible, Expandable and Continuous methods
35