Freshwater Availability in the Mississippi River Basin and Adjacent Texas Aquifers Under Human and Climate Pressures

Abstract The Mississippi River Basin and adjacent Texas aquifers (MRB–TX) face intensifying water stress from irrigation demand, extremes, and climate change. We quantify spatiotemporal storage trajectories by integrating long‐term groundwater‐level records, GRACE/GRACE‐FO terrestrial water storage anomalies (TWSA), irrigation water‐use reanalysis, drought diagnostics, and CMIP6 precipitation projections. Over 1950–2024, aquifer‐mean groundwater levels declined by ∼16.7 m in the Central and Southern High Plains and ∼15.2 m in the Carrizo–Wilcox, whereas humid northern and eastern aquifers were broadly stable and a midcontinent belt showed near‐zero net change. GRACE‐based TWSA indicates net losses of 85 ± 15 km 3 since 2002 in the arid western MRB–TX, gains of 152 ± 57 km 3 in the Great Lakes and northern Plains, and changes that are not distinguishable from zero (32 ± 30 km 3 ) in the lower Mississippi and Gulf Coast. Irrigation withdrawals averaged ∼52 km 3 yr −1 during 2000–2020 and were predominantly groundwater‐sourced, with pronounced peaks during drought years. Under SSP2‐4.5, most models project increased annual precipitation over much of the basin, driven by winter–spring wetting in humid regions and more uncertain summer changes, including potential drying in the arid west. Assuming continuation of recent groundwater‐level trends, portions of the High Plains and Carrizo–Wilcox aquifers are projected to cross −20 m relative to the 1950 reference level by mid‐century. Together, these results identify a longitudinal gradient in MRB–TX water storage and highlight the arid southwest as the region of greatest management urgency.