Human‐Induced Evapotranspiration in Indian Subcontinental River Basins

Abstract Quantifying human‐induced evapotranspiration (H‐ET) is essential for evaluating water availability in regions with extensive irrigation and groundwater pumping. However, H‐ET estimates over the Indian sub‐continental river basins have been lacking. Here, we estimate H‐ET across 12 major Indian river basins from 2003 to 2020 using GRACE‐based water balance estimates and natural ET simulations from five land surface hydrological models (HMs). GRACE‐ET consistently surpassed HMs‐ET, especially in dry seasons, highlighting unaccounted irrigation and groundwater pumping, with differences in mean annual ET exceeding 100 mm in a few river basins. H‐ET is more prominent during the dry season, contributing 30%–50% of total ET in irrigation‐intensive basins. Non‐accounting for H‐ET leads to considerable (more than 50%) overestimation in total Available water in the Indus, Mahi, and Pennar river basins, while 30%–40% overestimation in the Brahmani, Ganga, Godavari, Krishna, Tapi, Narmada, and Mahanadi basins. Uncertainty in H‐ET estimates arises from both Gravity Recovery and Climate Experiment (GRACE) products and HMs, with GRACE contributing ∼45% and HMs contributing ∼55% of the total uncertainty at the annual scale. H‐ET is dominated by irrigation from pumped groundwater in the Ganga and Indus basins, while surface water (runoff) contributes more in the Narmada and Mahanadi basins. These findings emphasize the need to integrate anthropogenic impacts in water budget assessments for sustainable water resource planning.