Implementation of satellite-based water accounting plus (WA+) framework for estimating groundwater balance and utilization in a semi-arid river basin of India

This study applied the satellite-based Water Accounting Plus (WA+) Framework wherein a WaterPix Model (pixel-based hydrological model) along with the Budyko hypothesis was used to account for the groundwater balance and utilization in the drought-prone Central Godavari River Basin (CGRB) of India as per the unique WA + based Land Use (WALU) classes. A reduction of 2.59 km³/year in the groundwater storage was observed during study period (2003–2020) despite the withdrawals of 8.88 km³/year against the total recharge of 13.4 km³/year, of which 12.22 km³/year was received from vertical recharge and 1.18 km³/year as the return flow (e.g., irrigation) to the groundwater. This may be attributed to the higher percentage contribution (∼54%) of the recharged groundwater to the baseflow. The higher baseflow contribution shows that surface water (SW)-groundwater (GW) interaction in the CGRB is high, and the ecological health of the basin is primarily sustained by the baseflow. The negative storage change in groundwater was also validated with the groundwater level data collected from 26 observational wells across the basin. Moreover, water demands (ET_Blue + ET_Green) were higher than the supplied water, resulting water scarcity in the CGRB for most of the districts. The consumptions from ET_Blue that is a measure of water consumption from irrigated crops suggests that the majority of water withdrawals (about 95%) originate from groundwater, revealing the basin's heavy reliance on this resource. Therefore, the marked ET_Blue hotspots (Nizamabad, Nirmal, Hingoli, parts of Nanded, Aurangabad, and Parbhani) are to be prioritised for reduced groundwater withdrawals and making ‘hotspots’ to the ‘bright spots’. The farmers of the ET_Blue hotspots regions should adopt less water-requiring crops (through crop diversification), such as millets and other coarse cereals to reduce water use in agriculture. Finally, the reliable quantification of groundwater supply and consumption using the WA + Framework can assist in groundwater resources management of a data sparse region.