El Niño Won’t Fill Up California’s Critical Groundwater Reservoirs

January 22, 2016 | 6:37 pm
Juliet Christian-Smith
Western States Regional Director

El Niño is hitting California at last, bringing the pitter-patter of rain, snowy mountains, and more wet weather in the weeks ahead. For me, El Niño’s arrival the last couple of weeks has been an opportunity to introduce my toddler to the joy of splashing in puddles—which have been practically nonexistent since she was born.

And while El Niño-fueled storms are beginning to fill above-ground reservoirs, it is important not to forget one of the major lessons of this drought: the critical importance of California’s groundwater. We recently released a fact sheet that describes the vital role groundwater has been playing in avoiding catastrophe for the Golden State in The Big Water Supply Shift: Groundwater Key to Water Security in California’s Changing Climate.

During the four-year drought, groundwater supplied half of California’s water. Unfortunately, it’s not raining underground. While aquifers can hold up to three times more water than surface reservoirs, they do not fill as quickly. In addition, our groundwater reserves have been depleted much more than those above-ground reservoirs that you are used to seeing pictures of—you know, the ones with the bathtub rings and the dry docks above parched soil that once was a lake bed.

The situation underground is far, far worse.

Groundwater: current problem

Rather than being low, many of California’s groundwater aquifers are completely tapped out and in negative territory. In the Central Valley, we have been withdrawing about 2 million acre-feet of water more than we replace each year for the last decade. Scientists estimate that excessive groundwater pumping over the last century has depleted Central Valley groundwater reserves by a total of 125 million acre-feet. That is about 4.5 times the capacity of Lake Mead, the biggest surface reservoir in the U.S.


Groundwater: future solution

Groundwater is California’s best strategy to buffer the impacts of climate change and to respond to the much more severe droughts we can expect in the future. Sustainable groundwater management can help protect California from both more severe droughts and floods. When it rains, we can slow sink, and capture runoff in the ground to recharge depleted groundwater aquifers by designing storm-water capture and management systems in urban areas and developing aquifer-recharge infrastructure in rural areas above accessible groundwater.

UCS is actively engaged in improving California’s groundwater management – playing an important role in the passage of the Sustainable Groundwater Management Act and currently working to ensure its effective implementation.

One wet season will have very little effect on our groundwater supplies. The only kind of rain that would refill our groundwater aquifers this year is of truly Biblical proportions—or else a steady flow of storms for years to come. So, while it is time to enjoy this rain, don’t be fooled into thinking California’s water problems will go away—they are still right underfoot.