As the climate changes, the water requirement of agricultural crops tends to increase. This leads to a higher irrigation requirement. At the same time, water availability falls, since water levels in many catchment areas of the Swiss Central Plateau decline in the summer. In order to identify areas with an increased risk of water shortage, a hydrological model was used to calculate the ratio of the potential irrigation requirement to the available supply (regional outflow) for 39 catchment areas during the period 1981–2010. The results show that in years with extreme climatic events such as 2003, the available supply in individual regions is already insufficient. Climate change causes this situation to intensify, leading in many cases to water shortages, as shown by modelling for selected areas based on two climate scenarios for the period 2036–2065. In the catchment areas of Glatt-Töss, Birs and Broye-Mentue, the frequency of water-shortage years rises many times in the event of dramatic climate change. In these areas, there is a demand for measures for appropriate water management which take account of the protection of waters as well as the demands of agriculture.
Irrigation requirement and available water supply under changing climatic conditions: a regional deficit analysis