Quantifying Agricultural Water Scarcity and Demand-Supply Dynamics in the Tapi Basin, India

Efficient water management in irrigated agriculture is crucial for sustaining food production and addressing water scarcity in semi-arid basins. In the Tapi basin, India, an imbalance between water withdrawals and agricultural water demand (AWD) has led to constant deficits and severe water scarcity. Using the SPHY-WA framework, this study quantified water withdrawals, consumed water, and water scarcity for irrigated croplands from 2003 to 2020. Average agricultural withdrawals were 12.0 BCM/year, primarily sourced from groundwater (83%), while AWD was estimated at 39.0 BCM/year, resulting in an average water deficit of 26.0 BCM/year. Consumed water averaged 8.0 BCM/year, with 4.0 BCM/year contributing to return flows. The Water Scarcity Index (WSI) analysis revealed severe to extreme water scarcity (WSI > 1) across the basin, with critical hotspots in Nashik, Jalgaon, Buldana, Aurangabad, and Dhule districts. Temporal trends showed declining withdrawals and stable demand, widening the supply-demand gap, particularly during dry years. Inefficient irrigation, excessive blue water evapotranspiration, and extensive cropland acreage were identified as key contributors to water scarcity. This study underscores the need for improving irrigation efficiency and optimizing water use in agriculture. The integration of WSI into the SPHY-WA framework enhances spatiotemporal analysis, providing actionable insights for sustainable water resource management in water-stressed regions.