Use of freshwater resources

Indicator Specification
Indicator codes: CSI 018 , WAT 001
Created 04 Jun 2015 Published 21 Mar 2016 Last modified 26 Aug 2016, 09:42 AM
Topics: ,
The Water Exploitation Index Plus (WEI+) is the total water use as a percentage of the renewable freshwater resources in a given territory and time scale.

Assessment versions

Published (reviewed and quality assured)


Justification for indicator selection

Monitoring the efficiency of water use is important for the protection, conservation and enhancement of the EU’s natural capital. it also helps to improve resource efficiency, which is included as an objective of the EU's Seventh Environment Action Program to 2020.
This indicator shows how total water use puts pressure on renewable water resources by identifying areas (sub-basins or river basins) with high seasonal abstraction in relation to the resources they contain, making them prone to water stress. The WEI+ is a water scarcity indicator that provides information on the level of pressure that human activity exerts on the natural water resources of a particular territory. This helps to identify those areas prone to water stress problems (Faergemann, 2012). The purpose of implementing the WEI+ at spatial (e.g. sub-basin or river basin) and temporal (monthly or seasonal) scales that are finer than the annual average at the country scale is to better capture the balance between renewable water resources and water use. This is done in order to assess the prevailing water stress conditions across Europe. In some basins, water scarcity is reflected only when calculating the indicator using the monthly WEI+, but is not necessarily captured by it. 

Scientific references

Indicator definition

The Water Exploitation Index Plus (WEI+) is the total water use as a percentage of the renewable freshwater resources in a given territory and time scale.


Percentage of water use over renewable water resources. Absolute volume of water is presented in million cubic meters (million m3 or hm3)


Policy context and targets

Context description

The objective of the EU's Seventh Environment Action Programme to 2020 is to ensure the protection, conservation and enhancement of the EU’s natural capital and to improve resource efficiency. Monitoring of the efficiency of water use in different economic sectors at national, regional and local levels is necessary to achieve this. The WEI+ is part of the set of water indicators published by several international organisations such as UNEP, OECD, EUROSTAT and the Mediterranean Blue Plan. There is an international consensus about the use of this indicator.

The indicator describes how total water use puts pressure on water resources and identifies areas (e.g. sub-basins or river basins) with high abstraction on a seasonal scale in relation to the resources available, and that are therefore prone to water stress. The changes in WEI+ help to analyse how the changes in water use impact on freshwater resources by adding pressure to them or by making them more sustainable.


There are no specific quantitative targets directly related to this indicator. However, the Water Framework Directive (2000/60/EC) requires Member States to promote sustainable use of water resources based on long-term protection of available water resources and ensure a balance between abstraction and recharge of groundwater, with the aim of achieving good groundwater status by 2015.

Having agreed thresholds of water exploitation index plus (WEI+) is quite important for  delineating non-stress and stress areas.  Raskin et al. (1997) suggests a WEI value above 20 % indicates water scarcity whereas a value higher than 40% indicates severe water scarcity. These thresholds are commonly used in scientific studies (Alcamo et al, 2000). Besides, Smakhtin, et al., (2005) suggest that 60 % withdrawal from the annual total runoff would cause environmental water stress. Since no formally agreed thresholds are available for assessing the water stress conditions across Europe, in the current assessment 20 % threshold as proposed by Raskin at al. (1997) is applied to distinguish stress and non-stress areas while 40% is used only as the highest threshold for mapping purposes.


Related policy documents

  • 7th Environmental Action Programme
    DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’
  • Addressing the challenge of water scarcity and droughts in the European Union
    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.
  • Water Framework Directive (WFD) 2000/60/EC
    Water Framework Directive (WFD) 2000/60/EC: Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy.

Key policy question

Is the abstraction rate of water sustainable?

Specific policy question

Water abstraction by source

Specific policy question

Is the use of water by sectors sustainable?


Methodology for indicator calculation

In 2011, a technical working group, which developed under the Water Framework Directive Common Implementation Strategy, proposed the implementation of the Regionalised Water Exploitation Index Plus (WEI+). This moved away from the previous approach, enabling the WEI to depict more seasonal and regional aspects of water stress conditions across Europe. This proposal further was approved by the Water Directors in 2012 as one of the awareness raising indicators.

The regionalised WEI+ is calculated according to the following formula:

WEI+ =  (Abstractions - Returns)/Renewable Water Resources

Renewable water resources are calculated as (ExIn + P – Eta - ΔS) for natural and semi-natural areas and as (Outflow + (Abstraction - Return) - ΔS)  for densely populated areas.


ExIn = External Inflow
P = Precipitation
ETa = Actual Evapotranspiration

ΔS = Change in storage (lakes and reservoirs)

Outflow = Outflow to the downstream/Sea

It is assumed that there is no pristine or semi-natural river basin district or sub-basin in Europe. Therefore, the formula of (Outflow + (Abstraction - Return) - ΔS) is used in estimating the renewable water resources.

  1. Climatic data was obtained from the EEA Climatic Database, which was developed based on the ENSEMBLES Observation (E-Obs) Dataset (Haylock et al., 2008). The State of the Environment database has been used for validating the aggregation procedure of the E-OBS data to the catchment scale.
  2. Stream flow data has been extracted from the EEA Waterbase - Water Quantity database. This database does not have sufficient spatial and temporal coverage yet. In order to fill the gaps, JRC LISFLOOD data (Burek at al, 2013) has been integrated into the stream flow data. The stream flow data covers Europe in a homogeneous way for the years 2002-2012 at monthly scale.
  3. Once the data series are complete, the flow linearisation calculation is implemented, followed by a water asset accounts calculation, which is done in order to fill the data for the parameters requested for the estimation of renewable water resources. The computations are implemented at different scales, independently from sub basin to river basin district scale. 
  4. Urban Waste Water Treatment Plants, E-PRTR database, Eurostat population data and JRC data on the crop coefficient of water consumption has been used for quantifying the water demand and water use by different economic sectors. Eurostat tourism data and data on industry in production has been used to estimate the actual water abstraction and return on a monthly scale. Where available, State of the Environment and Eurostat data on water availability and water use has also been used at aggregated scales for further validation purposes. 
  5. Once water asset accounts are implemented according to the United Nations System of Environmental Accounting Framework for Water (2012), the necessary parameters for calculating water use and renewable freshwater water resources are harvested.
  6. Afterwards, the bar and pie charts were produced, together with the static and dynamic maps.

Methodology for gap filling

LISFLOOD data of Joint Research Centre has been used in filling the gap in the stream flow data. The spatial reference data for the Water Exploitation Index Plus is Ecrins (250 m vector). Ecrins is a vector spatial data while LISFLOOD data is 5 km raster. In order to fill the gaps in the streamflow data, centroids of the LISFLOOD raster have been identified as fictitious stations. Topological definition of the drainage network in Ecrins has been used in snapping the most relevant and nearest LISFLOOD fictitious stations with EEA-EIONET stations and the Ecrins river network. Then locations of stations between EIONET and LISFLOOD have been compared and fully overlapping stations have firstly been selected for the gap filling. For the remaining stations the following principles have been implemented; fictitious stations have to be located within the same catchment with the EIONET station and share the same main river segment. In addition, both stations should provide strong correlation.

Methodology references

  • Alcamo et al. 2000 Alcamo, J., Henrich, T., Rosch, T., 2000. World Water in 2025 - Global modelling and scenario analysis for the World Commission on Water for the 21st Century. Report A0002, Centre for Environmental System Research, University of Kassel, Germany
  • EC 2012a Preparatory Action, Development of Prevention Activities to halt desertification in Europe, Service Contract to contribute to the building of Water and Ecosystem accounts at EU level. Part 1.
  • EC 2012b  Preparatory Action, Development of Prevention Activities to halt desertification in Europe, Service Contract to contribute to the building of Water and Ecosystem accounts at EU level. Part 2.
  • Kurnik, B., Louwagie, G., Erhard, M., Ceglar, A. and Bogataj Kajfež, L., 2014. Analysing Seasonal Differences between a Soil Water Balance Model and In-Situ Soil Moisture Measurements at Nine Locations Across Europe. Environmental Modeling & Assessment 19(1), pp. 19–34.
  • Raskin, P., Gleick, P.H., Kirshen, P., Pontius, R. G. Jr and Strzepek, K. ,1997. Comprehensive assessment of the freshwater resources of the world. Stockholm Environmental Institute, Sweden. Document prepared for UN Commission for Sustainable Development 5th Session 1997 - Water stress categories are described on page 27-29.
  • Smakhtin, V., Revanga, C. and Doll, P. 2005.  Taking into account environmental water requirement in global scale water resources assessment. IWMI the Global Podium.
  • ETC ICM, 2015. CSI 018 Use of freshwater resources in Europe (WAT01). Supplementary document to the draft indicator sheet.  

Data specifications

EEA data references

  • No datasets have been specified here.

Data sources in latest figures


Methodology uncertainty

Reported data on water abstraction and use does not have sufficient spatial and temporal coverage. Therefore, modelling with proxies needs to be implemented in order to assess net water use. First, water demand is calculated and afterwards this is compared to the production level in industry and tourism movements in order to approximate actual water use on a given time resolution. This approach does not have the ability to assess the justification of variations (i.e. resource efficiency) in water use over the time series. 
Due to the reference volume of reservoirs and lakes not being available, the water balance for reservoirs can only be quantified as a relative change, and not as the actual volume of water. This masks the understanding of actual water storage in, and abstraction from the reservoirs. Thus, the impact of residence time between water storage and water use from reservoirs is unknown. 
The sectorial use of water does not always reflect the relative importance of the sectors in the economy of a given country. It is, rather, an indicator describing which sectors environmental measures need to focus on in order to enhance the protection of the environment.

Data sets uncertainty

Quantifying water exchange between the environment and the economy is, conceptually, a very complex issue. A complete quantification of the water flows from environment to economy and, at a later stage, back to the environment, requires detailed data collection and processing which is not available at European level. Thus, reported data has to be combined with some modelling to construct the data for quantifying such water exchange, with the purpose of developing a good approximation to “ground truth”. But the most challenging issue is related to water abstraction and water use data as the water flow within the economy are quite complex to monitor and assess under current data availability. Therefore, several interpolation, aggregation or disaggregation procedures have to be implemented at finer scales, with both reported and modelled data.

-Due to errors in coordinates of the stream flow stations that reported, the estimated Water Exploitation Index Plus values have uncertainties, as does water use by sector for Cyprus.

- Andalusia Mediterranean Basin; eventually a substantial difference between local estimate (WAMCD Project-07.0329/2013/671291/SUB/ENV.C1) and the EEA estimate is subject due to the data precision and methodologies implemented.  EEA results for the Andalusia Mediterranean Basin looks underestimated compared to the local estimation.

Because of errors in flow linearization computation, the WEI+ results are not available for the following sub-basins:

- Drau and Sava of the Danube River Basin;

- Rhine coastal sub-basin of the Rhein River Basin;

- Elbe coastal catchment; and

- Weser coastal catchment.

Rationale uncertainty

Due to the aggregation procedure used, slight differences exist between sub-basin and river basin district scales for total renewable water resources and water use.

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata

Responsibility and ownership

EEA Contact Info

Nihat Zal


European Environment Agency (EEA)


Indicator code
CSI 018
WAT 001
Version id: 2
Primary theme: Water Water


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Frequency of updates

Updates are scheduled once per year


DPSIR: Pressure
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)

Related content

Data references used

Data used

European catchments and Rivers network system (Ecrins) European catchments and Rivers network system (Ecrins) Version 1, Jun. 2012 - Ecrins is acronym for European catchments and Rivers network system. It is a geographical information system of the European hydrographical systems with a full topological information. Ecrins is a composite system made from the CCM developed by the JRC, Corine land Cover, WFD reporting elements, etc. It is organised from a layer of 181,071 “functional elementary catchments (FECs)” which average size is ~62 km2, fully connected with explicit identifier (ID) relationships and upstream area. Catchments are grouped as sub-basins, river basin districts (actual and functional to meet hydrographical continuity). The catchments are as well organised according to their sea shore of emptying to meet Marine Strategy delineations. Catchments are drained by 1,348,163 river segments, sorted as “main drains” (connecting together the FECs) and secondary drains (internal to a FEC). river segments mimic the natural drainage, however fulfilling the topological constraint of “0,1 or 2 upstreams, single or 0 downstream”. Each segment is populated with distance to the sea, to ease further processing. They are connected to elementary catchments and nodes documented with altitude. Segments are as well documented with a “dummy river code”, fully populated that earmark each segment with the most distant to the outlet in each drainage basin and, everywhere this has been possible, with a “true river” ID based on river naming. A layer of lakes and dams has been elaborated. Lakes polygons (70,847) are taken from Corine Land cover , WFD Art. 13 and in some cases, from CCM “water layer”. Lakes inlets and outlets are set with the segment ID and where relevant, the dams making the lake is documented. All lakes which depths and volume was found have been updated. Version 1.0 here presented still contain some topological errors (e.g. incorrect segment branching), because inaccurate geometry. They are noted and a correction procedure is underway.

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