Urban Stormwater to Enhance Water Supply.

The capture, treatment, and recharge of urban runoff can augment water supplies for water-scarce cities. This article describes trends in urban stormwater capture for potable water supply using examples from the U.S. and Australia. In water-limited climates, water supply potential exists for large scale stormwater harvesting and recharge, such as neighborhood-scale and larger projects. The beneficial use of urban stormwater to meet nonpotable water demands has been successfully demonstrated in the U.S. and internationally. However, in terms of potable water use in the U.S., the lack of a regulatory framework and uncertainty in treatment and water quality targets are barriers to wide-scale adoption of urban stormwater for recharge, which is not so evident in Australia. More data on urban stormwater quality, particularly with respect to pathogens and polar organic contaminants, are needed to better inform treatment requirements. New technologies hold promise for improved operation and treatment, but must be demonstrated in field trials. Stormwater treatment systems may be needed for large-scale recharge in highly urbanized areas where source control is challenging. The co-benefits of water supply, urban amenities, and pollution reduction are important for financing, public acceptance and implementation-but are rarely quantified.