As climate change is making weather patterns more erratic, water supply for agriculture is becoming increasingly uncertain. This is particularly concerning in the highly agricultural Serbian Danube River Basin, where crops are mainly rainfed and the growing season is becoming warmer and drier in recent years. Assessing the balance between future agricultural water demand and availability under changing climate is critical to developing strategies to combat water scarcity challenges. To understand how changing precipitation and temperature affect water availability in this region during 2041-2070, we implemented the Soil and Water Assessment Tool+ hydrological model integrated with high-resolution crop rotation, irrigation, and bias-corrected regional climate projection data under two representative concentration pathways (RCP4.5 and RCP8.5). Results suggest that declining precipitation, increasing evaporative demand, and lack of widespread irrigation will intensify green water (i.e., soil moisture from rainfall that rainfed systems mostly rely on) scarcity (GWS) and crop water stress (CWS) across the spring-planted, rain-fed cropping systems in Serbia, particularly during the peak growing season. Cropping systems currently under irrigation (i.e., using blue water from fresh surface and groundwater) that are barely offsetting GWS and CWS will likely face the challenge of meeting an additional 10-20% increase in irrigation water demand in the future. These findings highlight that Serbia will need to increase agricultural productivity and even expand irrigated area to tackle increased water demand, but this may reduce future blue water availability.
