Replenishing California's aquifers

Water is a perennial topic in California. How much rain is falling, and where? How can we get cities and farmers to use less? How fast are we sucking it from underground aquifers? And, of course, how can we get more?

UC Santa Cruz professor Andy Fisher and his graduate student Sarah Beganskas are working on that last question. They’re building percolation ponds in the Pajaro Valley, on the central coast of California. Their goal is to replenish groundwater, which we’re using faster than nature alone can replace. The idea is to capture excess storm water before it gushes out to sea. (Recently, I wrote about their work for the San Jose Mercury News.) 

One problem with collecting storm water is that it can pick up fertilizers and pesticides as it cascades across the landscape. The UCSC scientists are trying to figure out how to deal with that issue; one idea is to enlist the help of bacteria. Adding a layer of microbe-harboring wood chips to infiltration basins might reduce pollutants before water soaks into the aquifer below. Early results from tests Beganskas and Fisher are running at Watsonville's Harkins Slough suggest that wood chips alone may not be enough, though. The microbes need time to work, so the researchers will experiment with slower infiltration rates in future trials.

When it rains, water collects in this infiltration basin at Harkins Slough, then percolates through the soil to recharge the groundwater below. (Image by USDA/Lance Cheung)