Integrated modelling of water supply and water demand using the example of irrigation farming in Saxony

摘要

As a positive effect of the projected climate change, an increase in potential crop yield in North and Central Europe is expected, if the simultaneously increasing water demand can be fulfilled. The future crop yield development and the associated irrigation water demand were investigated using the example of potatoes in Saxony, Germany. The relationship between the applied irrigation water amount and the resulting yield is assessed by means of a biophysical crop growth simulation model and further analysed on the basis of stochastic crop water production functions. These production functions reveal the required irrigation water demand for specific yield levels while considering different climatic conditions and soils. Taking account of factors such as climate, soil, and cultivars does not only supply expectation values, but also enables a quantification of associated uncertainties. The spatial distribution of the simulated irrigation water demand is compared to the spatial distribution of water potentially available for irrigation. The simulation results show that an irrigation of potatoes under current climate conditions is only reasonable in locations with low precipitation or in soils with a low water storage capacity. Only minor changes in the development of the irrigation water demands and potential yields are simulated by the model until the mid of the 21st century. Considerable yield declines of up to 25 % under non-irrigated conditions and prominent yield increases of up to 40 % under irrigated conditions are projected for large areas of Saxony, during the second half of the century. However, only 50 % of the water required for an optimal plant development can be delivered by precipitation in this period. The presented results may support decisions of policy makers on the regulation of regional water demands and simultaneously inform farmers about the profitability of irrigation systems at their sites.