Spatial and temporal patterns in water limitations caused by human water use in the conterminous U.S.

Water availability is fundamentally important to human well-being, economic vitality, and ecosystem health. The United States Geological Survey (USGS) recently completed a comprehensive assessment of water availability in the United States which included water supply, human water consumption, water quality, and ecological flows. The assessment relied upon national-scale models of natural and human processes including hydrologic conditions and human water consumption. Surface water total nitrogen and phosphorus concentrations were assessed along with groundwater nitrate and arsenic concentrations and ecologically relevant streamflow alteration. From 2010–2020, around 27 million people lived in areas where water consumption was > 80 % of water supply and therefore likely to experience regular water limitations. Water limitation was most severe in areas with high withdrawals for crop irrigation. The areal extent of potential water limitation was greatest in 2012–2013 during an unusually hot and dry period and coincided with elevated withdrawals for crop irrigation. Total nitrogen and phosphorus concentrations were elevated in surface water in many parts of the conterminous U.S. (CONUS), particularly agricultural areas. Regional comparisons showed that areas with the most severe water use imbalances also tended to have the highest concentrations of nutrients in surface waters and groundwater contaminants. The analysis highlights the multifaceted ways that excessive human water consumption can create water availability limitations.