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Two Boosts for Conjunctive Use

Acres of shallow ponds that let water percolate into the earth and wells that force water back underground instead of pumping it out may eventually be common features of the California landscape if new efforts to make better use of the state's underground water and storage space succeed. In September, Governor Davis signed new legislation aimed at helping local agencies better understand and manage their groundwater resources. A few weeks later, CALFED awarded more than $2 million in grant funds to five pilot projects designed to better coordinate the use of surface and groundwater - so-called conjunctive use - to help slake the state's relentless thirst.

The Local Groundwater Management Assistance Act will initially provide up to $5 million in grant funding to help local agencies undertake costly scientific studies of their aquifers. "Getting resources to the local area to help them develop a good understanding of geological and hydrological conditions is the first step towards successful conjunctive management," says David Guy of the Northern California Water Association, which sponsored the bill. "Ultimately this could benefit the entire state as well as the local areas." Guy says that a thorough assessment of such issues as the recharge rate - the rate at which the underground supply replenishes itself - and groundwater flow direction are critical. "You really have to understand the resource before you can figure out how much you can take out."

Meanwhile, several of the CALFED-funded projects will explore ways to "encourage folks to implement projects that make more use of underground storage capacity to improve supplies throughout the state," says CALFED's Mark Cowin. The CALFED framework for solving California's water woes calls for the state to increase its groundwater storage capacity by 500,000 to 1 million acre-feet.

CALFED funds will pay for a variety of projects, including studies of the economic, institutional and environmental impacts of developing a conjunctive use program and the impact of certain pesticides; several kinds of groundwater recharge projects; and monitoring wells. For example, the City of Tracy plans to construct wells and pipelines that will let it bank 2,000 af/yr of treated Delta Mendota Canal contract water in the local aquifer, while the North San Joaquin Water Conservation District will spread surplus wet-year water from the Mokelumne River on four acres of recharge ponds for extraction and discharge into the river during dry years. The feasibility of recharging depleted local aquifers - a cornerstone of conjunctive use - depends on a number of factors, say experts. A reasonably efficient injection well can recharge about 500 af/year, says CALFED consultant Anthony Saracino, but it's expensive and water quality must be very high. On the other hand, the percolation rate for recharge ponds varies depending on the soil type - the sandier the better - with about one-third foot a day considered decent. At that rate, a one-acre pond would recharge a little over 120 af/year.

Technical issues aside, the real difficulties of widespread conjunctive use are political, say Saracino and others. "People are very hesitant to give other entities access to their groundwater," says Cowin. "Particularly for farmers, there is a general anxiety that cities will just suck local aquifers dry. The Owens Valley is the monster in the closet." Indeed, many rural counties have approved local laws preventing the export of groundwater, and the Regional Council of Rural Counties has filed suit against CALFED, charging that the Record of Decision represents an effort to grab control of northern groundwater and send it south.

Because of these concerns, "local management" are the watchwords of conjunctive use efforts; in fact the CALFED grant program application package required applicants to satisfy certain criteria addressing the potential negative impacts of proposed conjunctive use operations, including groundwater depletion, third-party impacts and water rights issues. Guy says he thinks that as a result of CALFED, the state legislature will soon revisit groundwater issues, with some interests advocating a statewide system of regulation and others forcefully opposed. "I hope we can address everyone's concerns with a bill whereby districts can coordinate their locally controlled efforts on a larger scale to help meet the state's water needs," he says. Contact: David Guy (916) 442-8333; Mark Cowin (916) 653-2986 CH

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