Synthesis of public water supply use in the United States: Spatio‐temporal patterns and socio‐economic controls

Recent U.S. Geological Survey water‐use report suggests that increasing water‐use efficiency could mitigate the supply‐and‐demand imbalance arising from changing climate and growing population. However, this rich data have neither analyzed to understand the underlying patterns, nor have been investigated to identify the factors contributing to this increased efficiency. A national‐scale synthesis of public supply withdrawals (“withdrawals”) reveals a strong North–south gradient in public supply water use with the increasing population in the South contributing to increased withdrawal. Contrastingly, a reverse South–north gradient exists in per capita withdrawals (“efficiency”), with northern states consistently improving the efficiency, while the southern states' efficiency declined. Our analyses of spatial patterns of per capita withdrawals further demonstrate that urban counties exhibit improved efficiency over rural counties. Improved efficiency is also demonstrated over high‐income and well‐educated counties. Given the potential implications of the findings in developing long‐term water conservation measures (i.e., increasing block rates), we argue the need for frequent updates, perhaps monthly to annual, of water‐use data for identifying effective strategies that control the water‐use efficiency in various geographic settings under a changing climate. Key Points A North–south gradient across the country exists in public supply water use contributed by the increasing population in the South. Analysis shows water‐use efficiency has improved in urban counties relative to rural ones and in counties with higher income and education. Monthly update of water‐use data is critically needed to understand effectiveness of conservation measures in improving the efficiency.