Climate Change Drives Irrigation Expansion and Water Stress in the Serbian Danube

In the Serbian Danube River Basin, growing season droughts are increasing in duration and severity. Reliance on rainfed agriculture is widespread, and expansion of irrigation is necessary to counteract warmer and drier conditions. Quantifying current and future agricultural water demand and availability is critical for effective water resources management. This research integrates remote sensing with coupled hydrologicaleconomic modelling to map agricultural land use change, quantify changes in the water balance, and develop projections of mid-21st century irrigation expansion and water use. Annual cropland and irrigation maps were assimilated into the SWAT+ hydrological model and economic model. The economic model estimates how short- and long-run climate and water balance variables influence when and where irrigation becomes viable, and the hydrologic model estimates how water availability will change in response. Irrigation incentives increase in warmer and drier conditions and irrigation becomes viable for an additional 3-11% of fields by 2060 compared to 2020. Increasing crop water stress and declining soil moisture will require 10-20% increases in irrigation volumes to maintain the status quo. In total, irrigation expansion leads to additional water withdrawals of ~30 mm per year, which will exacerbate water balance deficits. The modest increase in irrigation expansion thus reflects that infrastructure constraints limit adaptation even though climate-driven incentives increase.