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A new study carried out by Stanford University shows an affordable solution is within reach for California's strained water supplies.

Published in San Francisco Estuary & Watershed, the study reveals the costs and benefits of using groundwater recharge and storage across the state. Known as "managed aquifer recharge" (MAR), the process 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 study co-author Debra Perrone, a postdoctoral scholar with Stanford's Water in the West program.

In general, the study found that MAR projects cost $410 per acre-foot per year compared to the median cost of surface water projects, which can be five times more expensive at $2,100 per acre-foot. MAR is particularly well suited to more developed areas that can take advantage of large quantities of treated wastewater and stormwater runoff where it can be collected by extensive infrastructures for use in recharge. Using excess surface water in more rural areas, MAR can play an important role in replenishing groundwater basins.

"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 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."

With groundwater supplying 60 percent of California's water supply, a changing climate and growing population are increasing pressures on dwindling supplies. A flexible approach to water storage could see more water agencies adopting MAR as a local management tool.