Projections of Freshwater Use in the United States Under Climate Change.

Water use in the United States reached its lowest level in 2015 in at least four decades. National trends, however, mask local challenges throughout the U.S. In some places, decreases in surface water use were more than offset by increases in groundwater use, leading to net increases in total withdrawals. Other places have seen increasing rates of water shortages caused by mixes of socioeconomic and climate forces. This study examines recent trends in freshwater use and makes projections in future freshwater use over the next 50 years. Projections are based on socioeconomic and climate scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report. Scenarios are paired with five climate models from the downscaled Multivariate Adaptive Constructed Analogs (MACA). We find total consumptive water use will decrease by as much as 8% under the best‐case scenario but increase by as much as 235% under the worst‐case scenario. Results depend on both climate and socioeconomic changes, but because agriculture is the dominant use of water in most regions, climate change impacts overwhelm all other factors under hot and dry futures. For the wetter climate models, water use decreases even under the highest emissions levels and highest population growth rates. Plain Language Summary: This study examines recent trends in water use and makes projections for future water use over the next 50 years. Projections are based on scenarios consistent with international climate assessments and provided for a wide range of climate models. Water use could decrease by as much as 8% under the best‐case scenario but increase by as much as 235% under the worst‐case scenario. Because agriculture is the largest user of water in most regions, impacts of climate change on water use are larger than impacts from non‐climate factors like population growth. Key Points: Dry regions see largest increases in freshwater use, with 8% decreases under best‐case scenarios but 235% increases under worst‐case scenariosDespite efficiency gains, population growth is expected to increase domestic water uses in fast growing regionsBecause agriculture is the dominant use of water in most regions, results vary more by climate model more than by socioeconomic scenario [ABSTRACT FROM AUTHOR]