Farmers toil at the mercy of nature’s whims, which can prove particularly vexing in California.
Even before climate change, bouncing between drought and deluge was routine in the Central Valley, the state’s richest farming region. Humans have amplified these natural cycles by pumping greenhouse gases into the atmosphere, studies show, creating a future filled with what scientists recently dubbed “whiplash events.”
California got a taste of whiplash four years ago, when one of its wettest winters immediately followed one of its deepest, longest droughts. Heavy runoff from rivers in the Sierra Nevada damaged the main spillway of the Oroville Dam, the largest in the nation, forcing more than 180,000 people to evacuate.
Such dramatic swings will create even more headaches for California farmers and water managers, who have more than their share in a good year.
Now, as California farmers grapple with reduced federal water allocations amid an intensifying drought, a recent study challenges policymakers to think about floods.
The increased frequency of extreme drought and flooding under climate change in the nation’s largest economy will intensify the already fierce competition for water, said Xiaogang He, a hydrologist who led the research while a postdoctoral scholar at Stanford University.
But the potential for more storms also points to an opportunity. If climate change is likely to unleash more floods on California, reasoned He, why not try to capture that water and send it to where it’s needed most.
In the study, published in Science Advances, He and his colleagues provided the first statewide analysis of the floodwater potentially available to restore depleted groundwater basins under future climate change scenarios. They found that the potential floodwaters increased toward the end of the century but that the extent to which the water could be used to replenish basins would be limited by constraints on the ability to capture and divert it.
Their analysis focused on the highest levels of streamflow likely to accompany future spikes in big storms. Harvesting those high-water flows, they concluded, could help mitigate flood risk while boosting the state’s dwindling groundwater supplies.
Those supplies are critically low in the backbone of the state’s $50 billion agricultural industry, the San Joaquin Valley. Farmers there have sucked so much water from the Tulare Basin to grow crops in an arid landscape that parts of the San Joaquin Valley, including one entire town, have sunk several feet.
The state’s groundwater sustainability law gives water managers roughly 20 years to replenish, or recharge, aquifers by balancing pumping and resupply levels.
Studies show that farmers may need to retire hundreds of thousands of acres worth billions of dollars to reduce groundwater demand and comply with the requirements of the sustainability law, said He, now assistant…