The demand for European Water Resources has increased from 100 km3 per annum in 1950 to 550 km3 per annum in 1990, with forecasts that this will increase to 660 km3 by the end of this Century (EEA, 1995). Such increase will, undoubtedly, result in future conflict between human demands (commercial, social & political) and ecological needs, most critically in periods of severe and extensive droughts. It is essential that techniques are developed to assess the frequency of droughts in European rivers and how these may change in the 21st Century.

The "Fight against Water Deficits" has been identified by the Task Force: Environment Water and this will be addressed by ARIDE by carrying out a pan European Study focusing on three key objectives. The first, is to understand the processes which control droughts with special emphasise on rainfall regimes, weather pattern and groundwater regimes. The second, is to develop methods for estimating the spatial distribution of drought statistics on an European scale. The third, is to develop techniques to predict the relative impact of future environmental change including climate variability and land use change. ARIDE will be supported by the UNESCO/FRIEND (Flow Regimes from International Experimental and Network Data) project which includes representatives of UNESCO, WMO, the European Environment Agency and the National IHP committees of European countries. ARIDE will have full access to the European Water Archive - a database of daily flow series and thematic data from 4,000 European rivers which has been established by the FRIEND project.

The objectives will be achieved by developing a consistent method for defining and analysing the temporal and spatial characteristics of European droughts. The analysis of regional drought characteristics, the development of a regional drought distribution model and a detailed process analysis using meteorological input data will be the basis to determine the relationship between drought severity and frequency in different regions of Europe. This will be complemented by developing relationships between droughts and climatic, geological (drought response index, groundwater recharge) and land use parameters. The model will be used to carry out a sensitivity analysis to evaluate the impact of changing rainfall and land use on the spatial and temporal probability distribution of hydrometeorological, surface water and groundwater droughts.
There will be two key deliverables of the ARIDE project. First, the result of a sensitivity analysis which will demonstrate the impact of environmental change on European droughts. Second, a software package which will provide a suite of methods which can be used subsequently by the European Water Industry to estimate the relative importance of different aspects of environmental change on European water resources.