Quantified groundwater–surface water dynamics across Tigris–Euphrates basin through integrated modelling

Water scarcity in Iraq’s Tigris–Euphrates basin is intensifying under climate change, upstream regulation, and increasing demand, creating pressure on groundwater and surface water sustainability. This study develops an integrated framework that merges Gravity Recovery and Climate Experiment groundwater anomalies, Global Land Data Assimilation System soil moisture fields, Moderate Resolution Imaging Spectroradiometer evapotranspiration, hydrometric observations, and machine learning to quantify groundwater–surfacewater exchanges. An extreme gradient boosting model predicts groundwater levels with R2 of 0.92 and root mean square error of 0.15 m. Results indicate groundwater storage declines ranging from −1.4 cm year−1 in the north to −0.9 cm year−1 in the south during 2002–2023, with seasonal deficits amplifying depletion. Exchange flux analysis reveals groundwater discharge sustaining rivers during droughts and flood-induced recharge during high flows. Scenario projections to 2050 show moderated depletion under RCP4.5 but accelerated decline under RCP8.5, emphasizing the need for adaptive abstraction control and managed recharge strategies.