A spatially distributed assessment of water allocation in EU27 for Year 2000

ed water is not necessarily lost. Large fractions of domestic and industrial water and cooling water are returned to water bodies (purified or unpurified) and are available for re-use downstream. Irrigation water infiltrates the soils and can reach groundand surface water. The water is abstracted from a certain water body but often returned to another water body at another location. This could have a double-damaging effect: on the water body where the water is abstracted, having a mainly quantitative impact (subtraction), and on the water body where the water is returned to, having a quantitative (addition) and qualitative (pollution) impact. True water losses (consumptive losses) occur when water is effectively removed from the blue water cycle by transpiration and evaporation or storage (and export) as goods and products. Public water supply and household abstractions Domestic water is almost completely returned, as there are only few consumptive losses. EEA (2009) estimates that 80% of public supply water is returned to the environment and only 20% are actually lost. Water returns may be discharged to surface waters as well as to ground waters. In line with the available EUROSTAT data, it was assumed that household abstractions are returned to groundwater, as they imply on-site abstraction and wastewater treatment. Industrial abstractions For industrial abstraction, water may be used for cooling and manufacturing purposes, but it may also be stored in goods and products. Water returns may be discharged to surface waters as well as to ground waters. Regarding the preference for surface waters as abstraction source and requirements for waste water treatment, it was assumed that water is predominantly returned to surface waters. Agricultural abstractions (Irrigation) The main loss of irrigation water is crop evapotranspiration. Evapotranspiration values have been calculated by Wriedt et al. (2008, 2009b) and can therefore directly be included. A secondary loss is the water stored in crop biomass, which was neglected in this assessment. Water returns may occur to groundas well as to surface waters. A more precise assessment has to consider the interaction of surface runoff, soil percolation, and local groundwater flow and groundwater drainage. Part of water abstractions is lost before use due to leakage in the distribution network. The leakage reinfiltrates to groundwater. The fraction of water leakage can be substantial and ranges between 10% (DK) to 40% (Croatia) (EEA, 2009). Within this assessment, there were no specific data available allowing more precise estimation of leakage rates. Even given availability of national or even regional data, the leakage rates may vary considerable from one location to the other. Water returns from A spatially distributed assessment of water allocation in EU27 for Year 2000 20 public water supply, household abstractions, and industrial abstractions were estimated using the consumption rates described above. The returns attributed to irrigation were estimated as the difference between irrigation requirement and crop evapotranspiration. For ‘other’ abstractions, the same values as for public water supply were applied. The water returns to surface water and to groundwater were calculated as follows: • All returns from public water supply and industry were returned to surface waters by a ratio of 80% and to groundwater by a ratio of 20%. Wastewater treatment plants and direct discharges are typically connected to rivers. However, also wastewater infiltration to groundwater is applied, benefiting from natural purification and recharging groundwater bodies. Abstractions should be equal to the sum of supply and return before use (leakage). Therefore leakage is implicitly included in the abstractions. Lacking reliable country specific data on leakage losses, the 20% return to groundwater substitutes leakage to groundwater and re-infiltration of wastewater. • Household abstractions were returned to groundwater, assuming that water is abstracted for self-supply and the water is not treated or treated on-site and that surface waters are unlikely to provide water with drinking water quality without treatment. • Irrigation abstractions were assigned to surface water and ground water based on the ratio of surface runoff and groundwater discharge (baseflow index) as a surrogate measure for surface and groundwater availability. The calculation of this baseflow index is described in Wriedt et al. (2009d). • Other abstractions were returned to surface waters. • All water returns were spatially allocated to the entities where the water is used. 2.3 Specific aspects 2.3. 1 Cooling water abstractions for electricity production Cooling water abstractions were not included in total abstractions and treated separately. Cooling water is almost exclusively abstracted from surface water bodies (EEA, 2009) and returned immediately after use with minor losses. ‘Once-through’ systems return water directly after the cooling process with negligible consumptive losses (0.36%) but with considerably elevated temperature. Modern ‘cooling tower’ or ‘recirculation systems’ do not discharge heated water, but evaporation losses are higher (EEA, 2009). General rules-of-thumb can not be given. In contrast to other sectors, cooling water abstractions are highly localized and should be related to the location of dams and power plants. There are no obvious proxy-data that can be used for further disaggregation below regional level. Assuming uniform distribution within a NUTS region or using A spatially distributed assessment of water allocation in EU27 for Year 2000 21 inappropriate proxy-data introduces high uncertainty without adding value. Therefore data on cooling water abstractions were disaggregated to NUTS2 level only. Energy production was used as a proxyindicator. Nevertheless, cooling water abstractions can make up a considerable part of total water abstractions having qualitative impacts on water bodies (increasing water temperature). For the context of this research, focusing on general water balance assessment and groundwater pressures, cooling water abstractions are of minor relevance. 2.3. 2 Tourist pressure on water resources Tourism puts considerable pressure on water resources. First, tourism concentrates large number of people in holiday regions in addition to resident population. Approximately 200 million travellers visit the southern European region each year, their numbers are expected to triple until 2005 (De Stefano, 2004). Water consumption of tourists can be significantly higher than that of local population. For example, UNEP (2007) (in EEA, 2009) report that the average tourist staying in a Mediterranean hotel uses between 33% and 100% more water than the average local resident, whilst a luxury tourist can use up to 600% more. The additional water demand is often concentrated to a short period of the year, i.e. summer holidays. Tourism water demand is implicitly contained in the data for public water supply and households. The specific effect of tourism can theoretically be accounted for during disaggregation. EUROSTAT statistics on ‘Nights spent by tourists’ provide a starting point, as they reflect the touristic pressure integrating number of tourists and duration of stay. A breakdown to NUTS3 level was made using the ‘number of bedplaces’ as a proxy-measure. The ‘nights spent by tourists’ where converted into a population equivalent as ‘nights spent / 365’ times a tourism water use factor of 3, assuming that the overall tourist water use is 300% of resident water use. The population equivalent of tourism water use was further expressed as a tourism pressure calculated as ratio of population equivalent to resident population. The mass tourism putting water resources under pressure concentrates in small areas, i.e. along the seaside, in winter sport regions, and so on. Within NUTS3 regions, the spatial patterns are unlikely to correspond to the distribution of resident population. There are no straightforward proxies that can be used in further disaggregation, nor more specific statistics. At NUTS3 level, the specific impact of tourism is generally a small fraction of NUTS3 population and therefore too unspecific to include tourism effects explicitly at NUTS3 level. Therefore the specific tourism impact was not considered in the disaggregation of water demands. Nevertheless, the local impact can be considerable and future research should develop a reasonable approach for explicit consideration. A spatially distributed assessment of water allocation in EU27 for Year 2000 22 2.4 Available water resources Water available for runoff can potentially be exploited to satisfy water demands. This amount of water can be estimated from water balances as hydrological excess water (HXS) that remains from rainfall after accounting for evapotranspiration and that is available for surface and subsurface runoff. Practically, only a fraction of HXS can be used in a sustainable way, considering for ecological flows necessary to maintain ecosystem functioning. Also part of the water may be stored and discharged in water bodies which are difficult to exploit. HXS was calculated using a monthly water balance model. A detailed documentation of the model is given in Wriedt et al. (2009d). The model includes a simple correction of precipitation for snow storage and a soil water balance model based on Pistocchi et al. (2008) calculating actual evapotranspiration, surface runoff and infiltration. HXS was calculated as sum of surface runoff and infiltration (representing subsurface flow components). The actual implementation was set up for catchments across Europe using JRC’s HydroEurope Database (Bouraoui & Aloe, 2008), using climatic data from the MARS database (Micale & Genovese, 2004), soil data from the European Soil Database (ESDB 2.0) and land use information derived from CORINE landcover (ETC, 2005). The base