Water Supply Risk in the United States 2015-2050 Considering Projected Changes in Population and Thermoelectric Power Demand.

Examination of water supply risk is important to identify areas of potential insecurity and prioritize allocation of resources. This work builds on and advances a previous U.S. water supply risk analysis developed at county-scale resolution, which did not account for water flow between counties and identified some counties on major rivers as being at high risk. This limitation is addressed in the present study. The analysis utilized data from U.S. Geological Survey water use reports to assess current water supply risk and also projected water supply risk in 2050. Flow volumes were calculated using the Water Supply Sustainability Index (WaSSI) tool developed by the USDA Forest Service, enabling the analysis to account for changes in climate and hydrology and changes in water demand. A modified Water Risk Index (WRI) was formulated, including five factors to which scaled values were assigned. Results indicate that accounting for natural transfers of water in counties in addition to local precipitation reduced the risk profile of many counties, with a maximum of 36 classified as high or very high risk, compared to over 400 identified in the highest risk category in the previous analysis.