Impacts of Climate Change on Water Availability and Crop Yield in Germany

Under a warmer climate, crop growth and crop yield could be affected by many factors (e.g. increasing temperatures, CO2 fertilization and lower water supply) either positively or negatively. The present study aims in a) projecting the future water availability and low flow conditions in the five largest river basins in Germany, b) investigating the impact of climate change and CO2 fertilization on crop yield, and c) studying the potential of having two yields (e.g. winter wheat – summer barley) per year under a warmer climate. The eco-hydrological model SWIM (Soil and Water Integrated Model) was driven by four regional climate models (CCLM, REMO, STAR and Wettreg) to simulate daily river discharge and crop yield in five large river basins in Germany. The impact on crop yield was studied for the basins Ems and Elbe with the STAR scenario. When evaluating climate impacts, an adjustment of net photosynthesis to higher CO2 concentrations and a flexible crop rotation scheme based on the harvest index were used. As simulations show, until the middle of this century water discharge in all the studied rivers would be 8-30% lower in summer and autumn compared to the period 1961- 1990. The current 50-year low flow is likely to occur more frequently in western, southern and part of central Germany, especially at the end of this century. Winter wheat yield is likely to decrease by about 6-10% under the STAR scenario due to lower water availability. However, CO2 fertilization may compensate this negative effect and increase the crop yield by 9-14%. Besides, it is likely to have two yields (winter wheat-summer barley) per year in the Ems catchment after year 2030.