Posted on December 01 2016
It’s no news to anyone that California is trudging into its sixth year of drought. Last year’s El Niño brought relief to the northern half of the state, and left some good snowpack in the Sierra Nevada, but down south things are still pretty crispy. Central Valley farmers, who produce the majority of many crops for the whole nation, are still struggling. They’ve been pumping groundwater at unsustainable rates in order to stay in business. Some without access to groundwater have given up. But a study by Stanford University that came out in summer 2016 shows that there is more groundwater below the valley than previously thought. A lot more.
Water wells in the Central Valley are typically less than 1,000 feet deep. Wells have been getting deeper as the drought forces farmers to reach down farther—the water table has fallen as much as 50 feet in certain areas. While it has long been known that water stores exist at great depth, they were generally assumed to be too saline to be of use, and researchers had not done extensive water testing of deep aquifers. Using gas and oil well drilling data as well as gas and oil pool information, the Stanford researchers modeled a new groundwater scenario. The Stanford study shows vast stores of deep freshwater, from about 1,000 to 3,000 feet below the surface. Some of it is indeed salt-tinged, or brackish, but even that is thought to be good enough that it could be desalinated relatively easily. All told, the newly discovered supply nearly triples the amount of water previously estimated to exist there.
Hallelujah, right? Well, it’s hopeful news, but it comes with a number of qualifiers. Firstly, it’s expensive to drill so deep. While it could be a lifesaver for urban demand, it’s not thought to be economically viable for agricultural use. Agriculture uses in the neighborhood of four times as much water as do cities. Pumping up that volume of water is costly. As mentioned before, some of the water would need to go through a treatment plant to make it usable. In addition to the salt, the water might also have been contaminated with effluvia from oil and gas drilling operations which are present in close to a third of the sites where the deep water has been found. Fracking may or may not have contributed noxious elements to these water pools as well—the research to know conclusively hasn’t yet been done.
Unrelated to the quality of the water is the effect of simply removing the water from the ground. Land subsidence is a key problem in the Central Valley. The increased pumping brought on by California’s extended drought (and that done in years past) has caused the land to sink over 30 feet in some places. And all that sinkage has resulted from wells mostly shallower than 1,000 feet. This can have catastrophic effects on roads, buildings, bridges, and drainage systems such as canals, as the land broadly settles in uneven and unpredictable ways. If this newfound resource is heavily overtaxed, deep-storage strata will compress, never to regain their ability to fill with water.
So both the risks and the rewards are high for a state that is getting pretty desperate for water. The challenge will be to use the unexpected gift with caution so as not to compound problems already evident from previous uncontrolled extraction of underground water supplies.