Water demands from Las Vegas, Nevada, combined with years of below average precipitation have drained Lake Mead to record-low levels, leaving a white “bathtub ring” 100 feet high.

Some of the United States’ fastest-growing and most populous cities are located in the nation’s most arid areas, while some other areas with abundant water are only sparsely populated. For example, Las Vegas, Nevada, located in the Mojave Desert, was among the most rapidly growing U.S. cities from 2000 to 2009. People flocked to the already-parched city, despite record-low water levels at its primary water source, Lake Mead. Population growth has even led to water stresses in areas previously considered water-rich, such as Atlanta, Georgia.

Water reuse, wastewater reuse, and water recycling all generally mean the same thing: using treated wastewater for a beneficial purpose. The process of treating wastewater prior to reuse is called water reclamation.

Water reuse offers an opportunity to significantly expand supplies of freshwater in communities facing water shortages. Coastal areas of the United States, for example, discharge 12 billion gallons of wastewater into estuaries and oceans every day—an amount equivalent to six percent of the country’s total daily water use. Reusing this water would directly augment the nation’s total water supply.

In conventional municipal water systems, water from a river, lake, or aquifer is treated to meet drinking water standards before being distributed for all uses. After the water is used, the community’s wastewater—the water that flows down the drain or is flushed down the toilet—is treated to remove pollutants before it is discharged into downstream water bodies.

Although conservation and improvements in technology have reduced water use for some purposes, such as cooling thermoelectric power plants and other industrial uses, public (or municipal) water use continues to rise, driven in part by expanding and shifting populations. Data from Kenny et al. (2009).

Water reuse is the use of treated wastewater for beneficial purposes, which increases a community’s available water supply and makes it more reliable, especially in times of drought.