Assessing historical and future spatio-temporal dynamics of water footprints across climatically diverse zones of an agriculturally dominant river basin

Spatio-temporal evaluation of agricultural water use under both observed and future climate conditions is essential for identifying opportunities for water conservation and supporting sustainable farming practices. However, such basin-scale assessments across distinct agroclimatic regions remain limited. To address this gap, the present study examines variability in the water footprint (WF) under historical and projected climate conditions for an agriculture-dominated sub-basin of India's northern Indo-Gangetic Plain. The basin was categorized into four agroclimatic zones: Zone 1 (upper basin), Zones 2–3 (middle basin), and Zone 4 (lower basin). The WF was estimated for two major crops (sugarcane and wheat). The historical mean total WF was 242 m3/t for sugarcane and 1402 m3/t for wheat. A pronounced climatic gradient is evident across the basin: rainfall decreases and evapotranspiration (ET) increases from upstream to downstream, contributing to higher total WF in the lower basin. Zone 1 shows the highest wheat WF mainly because of lower crop production despite higher rainfall. Zone 4 shows high sugarcane WF because of low rainfall and high ET. The WF of both crops is dominated by blue WF (57% for sugarcane and 56% for wheat), indicating strong dependence on surface and groundwater. Future projections show a declining trend in overall WF, primarily due to improved crop yields. The spatio-temporal WF assessment shows notable variation across zones, indicating that uniform water policies are insufficient at the river basin scale under varying climate conditions. Therefore, this study emphasises and proposes zone-specific adaptation strategies to improve sustainable, climate-resilient agricultural water management.