Stormwater runoff comes from rain that flows over impervious surfaces, such as streets and rooftops. If captured, it can be used or stored to recharge groundwater aquifers.
Cities historically managed stormwater to prevent floods. But in recent years, state and local policies are shifting to use it as a way to increase water supplies.
For example, Los Angeles County voters in 2018 passed Measure W, a property tax projected to raise hundreds of millions of dollars annually to capture and clean up stormwater. As part of that effort, Santa Monica is capturing 1.6 million gallons of runoff from its pier area, treating it and then using it for irrigation and toilet flushing.
The benefits to Santa Monica are twofold: It keeps polluted runoff off its beaches and provides usable water.
Obstacles to capturing stormwater include inadequate funding, poor water quality and lack of regulations. Projects to capture, transfer and treat stormwater are often expensive and hard to put in place without grants and local bond measures.