Developing an approach to calculate the WEI for the Austrian Rhine catchment

Even though Austria is a water rich country, which uses approximately 3% of its water resources, regional and seasonal challenges to ensure the water supply might occur. To facilitate a long-term, sustainable strategy for water use, detailed information on available water resources and water demand as well as possible changes due to climate change are necessary. In the “Wasserschatz” project the current available groundwater resource and the water use for the following sectors: agriculture, public water supply, industry and selected services (technical snowing and golf courses) were elaborated.

For the Austrian part of the Rhine catchment, the Water Exploitation Index was calculated for the year 2016. Where applicable the abstraction data obtained in the “Wasserschatz” project were directly used in the WEI equation. The data for the WEI equation was obtained from very different data sources (measured data, estimated data, extrapolated data) a differentiated approach was needed for each type of data and for each sector.

A very important part of the WEI are the returns, for which a different method for each sector were developed (agriculture, public water supply, selected services, industry and energy). For agriculture it was assumed that water applied as irrigation was completely transpired into the atmosphere. For cattle, the abstraction data were calculated from the amount cattle, returns were estimated according to the milk production. The abstractions for the drinking water supply were obtained from a model developed by the Institute of Sanitary Engineering and Water Pollution Control at the University of Natural Resources and Life Sciences (Vienna), the returns are assumed to be a fixed factor from the abstractions.  For the Industry abstraction data were obtained from the water register(official notices) and from questionnaires (real abstraction data). The responses from the questionnaires were categorized according to company size and NACE codes and the data was extrapolated to other companies. For the returns either data from the water register was used or factors from literature were used.

To obtain the renewable resources the calculated outflow of the Rhine catchment was used. The water use in the WEI is described as the abstractions – returns, where all the water that stays in the catchment is considered a return. For a water rich catchment as the Rhine, the WEI is expected to be very low. In a future step the WEI index for the Austrian part of the Danube will also be calculated. Another planned improvement is to disaggregate the available data and calculate a seasonal WEI+.