after several weeks With near-constant rain and flooding, California is finally drying up — but hopefully not and also Dry as the state needs as much rain as possible to emerge from a historic drought. These are California’s most frenetic and conflicted times: Climate change has intensified dry seasons and heavy rains, switching the state’s water system back and forth between severe shortages and floods that overwhelm canals.
The solution to both extremes at the same time lies right under Californians’ feet: aquifers, which consist of subterranean layers of porous rock or sediment, such as gravel and sand, filled with rainwater soaked from the soil above. This water can come to the surface naturally to form springs, or wells can be dug to collect water. In modern times, powerful pumps can draw water from hundreds of feet deep.
California’s Central Valley is full of such aquifers, capable of storing some 46 trillion gallons of water, three times more than all of the state’s reservoirs. But this part of the country has long overexploited them; this 20,000-square-mile agricultural powerhouse grows 40 percent of the country’s fruits, nuts and other table foods. (Overall, agriculture accounts for 80 percent of all water use in California.) In extreme cases, this can collapse land, dropping tens of feet of elevation in some parts of California.
That creates a serious imbalance, said Graham Fogg, a hydrogeologist at the University of California, Davis, who studies California aquifers. “Civilizations around the world are really experts at drawing groundwater almost uncontrollably, but we’ve been terrible at putting water back into the ground,” he said. “It’s a bit like mismanaging a bank account, where you’re very good at withdrawing money, but you’ve neglected deposits for decades.”
To make matters worse, California’s mounting water debt is now due. The state’s system of open-air reservoirs is designed to collect water through the rainy season and then distribute it throughout the dry, Mediterranean-style summers. But during droughts, those reservoirs can drop to critical levels, as they did recently before hitting atmospheric rivers in late December and early January. On top of that, hotter temperatures end up evaporating more water.
But Fogg and his colleagues have a plan to balance the state’s water budget: use giant sensors suspended from helicopters and towed behind all-terrain vehicles to strategically target certain areas for aquifer recharge. They just need to find a site with the right geology.
Fogg and his The team is looking for ancient features called paleovalleys.
Interestingly, the subterranean waterways of the Central Valley are formed by the flow of water more thanground. The Sierra Nevada mountains bordering the valley’s eastern edge were once covered by glaciers. When the ice melts, the resulting rivers cut their channels and spew different kinds of sediment, which are deposited in layers. These are ancient valleys up to a mile wide and 100 feet deep. They’re very, very good at channeling water into the ground.
