Study recommends groundwater recharge as way against drought

A new Stanford University study recommends groundwater recharge and storage across the state of California as what it calls as "an affordable solution" against drought in recent years.

In addition to building more resilient water supplies in the Golden State, the study suggests that the process, known as "managed aquifer recharge," or MAR, can incorporate co-benefits such as flood control, improved water quality and wetland habitat protection.

"We find that MAR is an effective and affordable way to balance local groundwater decisions with regional and statewide management," said Debra Perrone, a postdoctoral scholar with Stanford's Water in the West program and co-author of the study published in San Francisco Estuary & Watershed.

The median cost of MAR projects is estimated to be 410 U.S. dollars per acre-foot, namely the amount of water required to cover an acre of level land at a depth of 1 foot, or about 30 centimeters, per year. By comparison, the median cost of surface water projects is five times more expensive - 2,100 dollars per acre-foot per year.

Groundwater supplies up to 60 percent of California's water supply during dry years. However, groundwater went largely unregulated until the 2014 passage of the Sustainable Groundwater Management Act.

While many local communities rely on statewide infrastructure to supplement their water supply, MAR allows for local water storage, access and management to a much greater extent than large surface water reservoirs, which are often managed by state and federal entities. Although excess surface water can be limited in some regions of California, treated wastewater and urban stormwater offer sources for MAR.

"Every year, California lets 1 million acre-feet of treated wastewater flow to the ocean," said co-author Melissa Rohde, previously a researcher with Water in the West. "Our research shows it would cost the state about 870 million dollars to build the necessary MAR facilities to recover and store this water. That's not a lot of money compared to the cost and energy required to transport water from large surface water projects or to desalinate ocean water."

As a changing climate, growing population and other factors put increasing pressures on water supplies, the need in California, as the largest and populous state in the United States, for long-term resilience will only intensify, the study noted. Therefore, it is likely that more water agencies will adopt MAR as a local management tool. Endit