In California, a move to ease the pressures on aging dams
WALNUT GROVE, Calif. — Until a few weeks ago, the McCormack-Williamson Tract in the California Delta was an island of low-lying farmland, more than 2 square miles protected from the surrounding rivers and sloughs by earthen levees.
Today, the tract is an immense lake, up to 15 feet deep, with fish prowling the water and ducks skimming the surface. The adjacent Mokelumne River, swollen by the intense storms that have drenched the state this winter, caused a levee to break, allowing the water to rush in.
Those same storms led to the recent near disaster at the Oroville Dam 100 miles north of here, which cast an uncomfortable light on the elaborate and aging network of reservoirs, aqueducts, levees and pumps that funnel water to the state’s 39 million people and its $50 billion agricultural industry.
The flooding at McCormack-Williamson was unintentional, but scientists and environmental groups say deliberately creating similar areas — floodplains to allow the state’s rivers to overflow more naturally and benignly — is a way to help ease the strain on this water infrastructure, especially as climate change poses new challenges.
“Nature has been dealing with the vicissitudes of water changes in California for millennia,” said Brian Stranko, director of the state water program for the Nature Conservancy, which bought the tract here, south of Sacramento, in 1999 and has long had plans to restore it. “There are certain things that nature can do that we can’t do as well.”
Moving some of the state’s 13,000 miles of levees back from rivers to make floodplains would allow dam operators to release more water without endangering population centers. Water percolating down through the flooded land also would help recharge aquifers, which, having been severely depleted by pumping for agriculture, are subject to a new state groundwater law requiring they eventually be made sustainable. And the flooding could restore some of the fish and wildlife habitat that existed in California’s interior valleys before intensive farming began a century ago.
But as with everything else involving water in California, the subject of augmenting the state’s so-called gray infrastructure of concrete dams, aqueducts and other structures with floodplains and other “green” infrastructure, including better-managed watershed forests, is one of intense debate. There are concerns new floodplains would take farmland out of production and that allowing benign flooding would reduce the amount of reservoir water available for agriculture and other uses.
“California water is complicated,” said Joshua Viers, a professor at the University of California, Merced, who was at the flooded tract last week with a team of researchers using water-sampling equipment and other instruments to monitor the changes taking place. “But I think we’re finding that there are softer paths.”