Ermittlung des regionalen Bewässerungsbedarfs für die Landwirtschaft in Bayern

The challenges associated with ongoing climate change will pose major challenges for global agriculture in the future and require well thought-out adaptation strategies. Thus, adaptation of water management is one of the major tasks to be tackled. Changes in the monthly water balance and precipitation depths and their intra-annual shift in favor of the winter half-year, as well as increasing evaporation rates, indicate that the availability of water is an limited production factor. These global changes can also be considered on a regional scale and are consequently also of high relevance in Germany. The regional representation of the scenario succeeds on the basis of the core ensemble of the German Weather Service (DWD). Based on these climate projections, the irrigation demand of Bavaria's agriculture is calculated in a model simulation. The model results are subdivided into arable crops, vegetable crops and special crops. Studies on irrigation demand done in the past at the Thünen Institute form the basis of the model development, which has been continuously optimized in the course of the project. The model approach is based on the principle of Geisenheim irrigation management where soil and crop-specific characteristics are used in addition to climate data to differentiate plants water requirements. This information is combined with spatial data on agricultural land use in Bavaria in order to estimate regional irrigation demands. In this study, the irrigation demands of Bavarian agriculture are simulated for the periods 1991– 2020 (ex-post period) and 2021–2050 (future). The mean irrigation demand of all considered crops increases, comparing the two observation periods. By 2050 the mean annual water demand is expected to increase by 19 %. Differentiated by land use classes, Bavaria's irrigation demand increases by 19 % in arable farming, by 23 % in vegetable growing and by 10 % in the cultivation of special crops. However, annual fluctuations in climatic conditions can lead to significant deviations from the mean trend. The spatial analysis of the model results displays a high degree of correspondence with the current irrigation regions of Bavaria. Thus, a high water demand of agriculture can be identified by the model in the regions Knoblauchsland, the wine-growing regions of Lower Franconia, the areas south of Regensburg and north of Augsburg. The model developed in this study has a high sensitivity to the input parameters and allows simulations of different time periods and study areas. The methodology could be improved and further developed. Also, the transferability to other projects and issues is given.