Prioritizing Underground Water Storage

Ways of recharging the aquifer (Water Education Fdn)

We've lamented that California has built very little water storage though

State voters have approved eight water bonds since 2000 that authorize some $27 billion in funding for various water projects.

California is now known for being a State that can't get any important project built, whether it be high-speed rail, low-cost housing, or hydroelectric dams.

It's time to prioritize below-ground storage.

Winter storms have filled California’s reservoirs and built up a colossal Sierra snowpack that’s nearly twice its normal size for this time of year. But years of dry conditions have created problems far beneath Earth’s surface that aren’t as easily addressed.

Groundwater — found in underground layers containing sand, soil and rock — is crucial for drinking water and sustaining farms. During drought years, 60% of California’s annual water supply comes from groundwater. This water is not easily replenished, especially as many groundwater basins across the state are critically overdrafted...

Compared with 2004, the amount of water on and below the ground in 2022 has dropped by nearly 55 cubic kilometers.

Recharge site in Selma, CA.

Hydrologist Jay Famiglietti, a professor at Arizona State University, and NASA scientist Pang-Wei Liu used satellite data and surface measurements to determine groundwater depletion. Of the 55 cubic kilometer total diminishment in California's water supply since 2004, approximately 40 cubic kilometers, or 73% came from groundwater.

Time for a little arithmetic. The acre-foot, which is the quantity of a sheet of water one acre in area by one foot deep, is a standard measure of water volume. The average household uses between one-half and one acre-foot per year. There are 810,714 acre-feet in 1 cubic kilometer. The two largest reservoirs in California, Shasta and Oroville, hold 5.6 and 4.3 cubic kilometers of water, respectively.

To create additional above-ground reservoirs the equivalent of Shasta and Oroville would cost many billions of dollars. If water from the snowpack could be directed to underground storage and then withdrawn when needed (we know that California has already taken out 40 cubic kilometers net), that method would be much more cost effective then building dams. Without human intervention six to nine wet years in a row would be required to replenish the aquifer.

Farmers, hydrologists, and agronomists realized one century ago that underground wells could fill faster if the land were managed to absorb flood waters. Today much more is known about Managed Aquifer Recharge (MAR), but little has been done since we last wrote about this subject seven years ago.

It makes sense to build more recharge stations on land that's already equipped for them. The financial, environmental, and regulatory obstacles are much less than other water-storage alternatives. If Californians blow it again, we are truly an undeserving people.