Spatially explicit and regionalized quantification of blue and green crop water footprints in a water-stressed river basin

Evaluating crop water consumption through the water footprint (WF) offers a valuable approach to optimizing water use. The study proposes a remote sensing method to quantify blue WF (BWF), green WF (GWF), and total WF (TWF) for crops in the upper Cauvery River Basin (UCB) using evapotranspiration (ET_a) datasets derived from the vegetation coefficients (<i>K_v</i>), rather than relying on generalized FAO <i>K_c</i> tables. Using a stacked ensemble algorithm, study downscaled ET_o and rainfall to a 500 m. Fine-scale seasonal BWF, GWF, and TWF for selected crops were mapped for the study period from 2015 to 2019. Our results show that while most crops predominantly depend on GW with minimal blue water extraction, paddy (Summer-IRR) and ragi (Rabi-RF) exhibit disproportionately high BWF, indicating critical hotspots of irrigation pressure and groundwater stress. Limited rainfall makes summer paddy strongly reliant on irrigation (BW), whereas Kharif maize utilizes GW, underscoring significant implications for water management policy. The high BWF and GWF values for ragi in 2016 highlight the impact of drought on WF, representing a distinction. This work provides a reference regional dataset of BWF, GWF, and TWF for the UCB, supporting improved understanding of water consumption dynamics, thereby informing future agricultural water management planning.