New water accounting reveals why the Colorado River no longer reaches the sea

Persistent overuse of Colorado River water in recent decades has drawn down major reservoirs and triggered mandatory use reductions. The river supports >40 million people and >2 million hectares of cropland. The authors compile a comprehensive water budget for 2000–2019 using primary data and modeled crop and riparian/wetland evapotranspiration to quantify direct human uses (municipal, commercial, industrial, agricultural) and indirect losses (reservoir evaporation, riparian/wetland evapotranspiration). Irrigated agriculture accounts for 74% of direct human uses and 52% of overall consumption. Water consumption for grass hay collectively totals 46% of all direct water consumption, helping explain why the river rarely reaches the sea.