Intensification of irrigated agriculture and precipitation explain rising evapotranspiration in the Snake River Basin despite declining atmospheric demand
Year: 2026
Type: article
Abstract: Evapotranspiration (ET) is the dominant water outflux in irrigated semi-arid basins, yet its long-term trends and drivers remain poorly quantified at management-relevant scales. In intensively irrigated systems operating under prior appropriation, detecting and attributing changes in consumptive water use is essential for sustainable water governance. Here we show, using OpenET ensemble estimates across 53 HUC-8 watersheds of the Snake River Plain over 2000–2023, corroborated by GRACE-derived water balance and Landsat net primary productivity, that ET increased significantly in 25 of 53 watersheds at a basin-wide median rate of 1.7 mm yr⁻¹ , driven primarily by irrigated area expansion (contributing to 54% of ET trend) and secondarily by precipitation (contributing to19% of ET trend), while declining atmospheric evaporative demand partially offset these gains. The region underwent a significant basin-wide shift toward dairy forage production, with alfalfa, other hay, and corn collectively increasing their share of cropland at the expense of small grains, indicating crop compositional intensification. Reliance on individual OpenET models had significant control on attribution inferences, with the irrigated fraction contribution to ET trends ranging from 11% (geeSEBAL) to 60% (SSEBop) across models compared to 54% for the ensemble. These findings demonstrate that land use intensification can override climatically driven declines in atmospheric evaporative demand. Additionally, inter-model uncertainty in remote sensing ET products is sufficiently large to alter water management conclusions.
Institution: University of Idaho
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,600
OpenAlex ID: W7223090044