Water banking is a form of conjunctive use in which water is allocated for current use, or stored in surface water reservoirs or in aquifers for later use.

Groundwater banking is part of a system in which surface and underground water supplies are alternately used so neither river nor aquifers are critically drawn down. In a twist of fate, the space made available by emptying some aquifers opened the door for the banking activities used so extensively today.

Groundwater Banking Overview

Using groundwater has always been essential in the arid West.

With this in mind, some water practitioners promote groundwater banking as the way to stabilize California’s water supply without the challenges associated with surface storage, and costs of building storage facilities.

A 2012 Public Policy Institute of California report, for instance, has noted that storing water underground can be a cost-effective way to save water for dry years, and could become increasingly important with changing climatic conditions.

Groundwater Banking Pros and Cons

Proponents of groundwater banking say the state should utilize the expansive natural underground storage capacity available in aquifers. Some water agencies have done so.

For example, during three dry periods the Santa Clara Valley Water District banked 20,000 to 30,000 acre-feet of water each year from supplies it received from the Central Valley Project and the State Water Project. The district can bank as much as 350,000 acre-feet of water. SCVWD has said groundwater banking creates a natural reservoir for the district, and one the district doesn’t have to build.

Elsewhere, the Arvin-Edison Water Storage District, located southeast of Bakersfield, has also used groundwater banking to provide reliable dry-year supplies.

North of Kern County, Madera Irrigation District proposes to construct a groundwater bank on the property known as Madera Ranch, west of the Madera.

And in 1988, California’s Department of Water Resources acquired 20,000 acres on behalf of the State Water Project to be used as a groundwater bank. The Kern Water Bank—30 square miles located on a large, undeveloped section of the Kern River’s sandy alluvial fan — is now operated by more than 400 farmers who grow a wide variety of crops, including almonds, grapes, citrus, alfalfa, and pistachios. The water bank serves a dual purpose as a water resource and wildlife habitat, where vulnerable and endangered native plant and animal species are preserved and protected.

Controversies

Water banking is not without controversy.

Skeptics of groundwater banking are wary of the potential for mismanagement, negative impacts to the environment and believe it could privatize a public resource.

Experts also say a successful groundwater banking program requires adequate groundwater data collection, monitoring and modeling. These components are key to determining aquifer characteristics, estimating groundwater banking capacity, simulating and verifying the short- and long-term fate of the stored water, and assessing the cost benefit of the project.