Researchers from UC Davis and UC Cooperative Extension are testing a new method for capturing excess water flows during California’s rainy season by diverting it from rivers into the network of canals running through Central Valley farmland, SFGate reports.
This irrigation system remains empty during the rainy months, and the scientists are exploring the possibility of filling some canals with water and directing it onto farmland where it can seep underground.
The method, called on-farm recharge, could help capture some of the expected upcoming El Niño heavy rains and refill California's dwindling groundwater supply.
The researchers have identified 3.6 million acres of California farmland that's suitable for recharge and say that flooding it with only one foot of water could add as much as 3.5 million acre-feet of groundwater, SFGate reports. This could help to replenish the 6 million acre-feet growers had to pump this year alone to cope with California's drought.
And the benefits of on-farm recharge go beyond collecting water. Flooded farmland can create wetland habitat for birds in winter, as well as replenish the deepwater aquifer can prevent land from sinking.
With the drought leaving lakes and reservoirs at historic lows, water districts and farmers are becoming increasingly dependent on groundwater. Between 70 and 80 percent of lost surface water in agriculture is being made up by pumping groundwater, SFGate reports.
To help identify which farmland is suited to managed flooding and groundwater recharge, the researchers developed an interactive map for farmers to help them determine whether their soil and crops are suited for the practice. However, the tool still needs more data on the effectings of flooding crops.
This technique could help answer the calls of scientists earlier this year, who warned that unless California can figure out a way to capture rainwater quickly, much of it will be lost to the ocean. California’s record-low snowpack this year actually may be far more historic than previously thought — at its lowest in more than 500 years, according to a paper published in September in the journal Nature Climate Change.
Snowpack is the most important part of California’s water supply — in a normal year melting mountain snow provides the state with one-third of its water. An additional third is pumped from underground aquifers, and the remainder comes from rivers and reservoirs.