Water quality is a continuing national concern, in part because the containment of pollution from nonpoint (diffuse) sources remains a challenge. We examine the spatial distribution of nonpoint-source threats to water quality. On the basis of comprehensive data sets for a series of watershed Stressors, the relative risk of water-quality impairment was estimated for the over 15,000 fifth-level watersheds in the contiguous United States. A broad division emerged at about the lOOth meridian, with eastern areas typically under higher stress than western areas, reflecting the generall higher housing, road, and agriculture densities and higher levels of atmospheric deposition in the eastern division. Recent trends in some Stresso are encouraging, but the prospect offurtlier substantial population growth indicates continued pressure on water quality, suggesting that renewed focus on controlling nonpoint-source pollution will be needed if the goals of the Clean Water Act are to be attained.

of counties in the United States saw net decreases in surface water withdrawals (Figure 1). Decreases were especially widespread throughout the Great Plains. The decrease came despite population increases, in large part due to structural changes in the U.S. economy that favored less water-intensive industries and broad efficiency gains in household appliances, thermoelectric power generation, and agriculture irrigation.National trends, however, mask challenges in many regions of the U.S. In some places (e.g., in Nevada and throughout the Mississippi River basin), decreases in surface water use were more than offset by increases in groundwater use, leading to net increases in total freshwater withdrawals. Other places have seen increasing rates of water shortages caused by mixes of socioeconomic and climate forces (Schewe et al., 2014;Warziniack & Brown, 2019). In 2018, over 1000 public water suppliers in Texas instituted water use restrictions in response to ongoing drought (Texas Commission on Environmental Quality, n.d.). A review by the Government Accountability Office found that 40 out of 50 state water managers expected water shortages to affect their state in the near term under what they describe as average conditions (U.S. Government Accountability Office (GAO), 2003).This study examines recent trends in freshwater use and makes projections for future freshwater use over the next 50 years. Projections are based on socioeconomic and climate scenarios from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5; IPCC, 2014). The scenario approach uses plausible

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