The Agricultural Structure Survey conducted by the Federal Statistical Office of Germany (Statistisches Bundesamt – Destatis) reports that in 2022 4.8% of Germany’s arable land was equipped with irrigation systems. Although this share remains low compared to many southern European countries, the relative increase of irrigated land—by almost 50% since 2009—is substantial. With rising temperatures and changing precipitation patterns projected as a result of climate change, this trend is likely to continue.

Since most irrigation water in Germany is sourced from groundwater, increasing irrigation demand can lead to resource-use conflicts and additional stress on groundwater reserves. When assessing the impacts of greater groundwater extraction for agricultural use, not only the total volume of water withdrawn is relevant, but also the fate of the irrigation water. While increased irrigation return flow will enhance groundwater recharge—a positive outcome from the perspective of water suppliers—it reduces the efficiency of irrigation from the farmer’s standpoint, as less water is used by the crops.

To analyze the quantity and distribution of irrigation water under projected future climate conditions in Germany, the crop model ExpertN was used to simulate crop production and potential irrigation demand in a 400 km² area south of Stuttgart. Agricultural land is predominantly arable and mainly used for growing wheat, barley, rapeseed and silage maize. The simulations employed 13 bias-corrected climate projections from the KLIWA ensemble as future climate scenarios. Soil properties were taken from the BK50 soil map.

Irrigation amounts were calculated based on the simulated soil water content for each soil–climate combination. Virtual irrigation events were triggered when soil moisture dropped below a crop-specific threshold, as defined by the Working Group for Agricultural Engineering and Agricultural Construction in Bavaria (ALB).

Finally, the annual amount of irrigated water and its pathways were analyzed and visualized. For most climate scenarios, irrigation demand showed no substantial increase compared to the historical baseline, although individual scenarios with markedly reduced summer precipitation indicated significant rises. The analysis also showed that most of the applied irrigation water contributed to increased plant transpiration, with a smaller fraction lost through soil evaporation. The portion of irrigation water that leaves the crop root zone to contribute to groundwater recharge generally remains small when irrigation is applied based on reliable soil moisture information.