Fossil water: A diminishing resource on the Southern High Plains

Groundwater depletion is a growing global issue, particularly in agricultural “breadbasket” regions dependent upon irrigation. This paper applies a spatially explicit process with MODFLOW-NWT to model groundwater levels in the Southern High Plains of the United States through 2100. We Incorporated recent (2013–2023) land cover, precipitation and population data alongside future projections under two climate scenarios (SSP2–4.5 and SSP5–8.5). Model validation against field-measured water elevations (2013–2023) yielded Nash-Sutcliffe and R2 values of 0.9921, mean error of 0.124 m, mean absolute error of 8.89 m, and a root mean square error of 12.648 m, suggesting a good fit with our approach. Both predicted climate scenarios forecast significant cropland expansion and population growth, driving increased groundwater extraction, leading to substantial depletion in the southern portion of the study region. Analysis of land capability classification reveals that future irrigation will increasingly rely on marginal soils. Our findings underscore the urgent need for adaptive soil and water management, including restoration of perennial grasslands to support ecosystem services and preserve water resources for both rural and urban populations. This study emphasizes that we must adapt our agricultural production methods to keep rural economies strong, especially given increasing uncertainty of how future conditions may cause water supplies to shrink.