As California plans for continued climate change, including the need to manage agricultural water use to comply with the Sustainable Groundwater Management Act (SGMA), a new report finds the intersection of energy with water and climate may not be getting as much attention as it deserves, especially in farm country.

“The Future of California’s Water-Energy-Climate Nexus,” from the Pacific Institute and Next 10, presents various scenarios for both urban and agricultural water and energy use. The researchers found that while agricultural land uses more water, the energy currently needed for that use is less than the energy needed for urban water use. The primary differences are in transport, potability and temperature. Some urban parts of the state get their drinking water from far away, and that movement has energy costs. Water for agricultural use is rarely treated to drinking water standards nor is it heated, two processes that are heavily energy-dependent and used in most urban and suburban contexts.

“If you look across that whole managed water cycle, it's the end use that's the most energy intensive,” said Heather Cooley, research director at the Pacific Institute and one of the report’s authors. “That's what we're doing in our homes, in our businesses. And a lot of that is heating water.” The energy used for pressurization to irrigate fields, for example, is much less, relatively speaking. Ag use also doesn’t generate wastewater, which requires further energy use for treatment, she said.

In the report scenario with the most intense climate impact, the researchers identified significant urban encroachment, which would take land out of agricultural production. That means less overall water use but with greater energy needed for the water that is used. For urban users, as the energy grid becomes less carbon-dependent, Cooley said shifting water heaters from natural gas to electric will reduce urban water energy use. Agricultural use will similarly benefit from a greener grid for its water’s limited energy needs.

In a virtual presentation about the findings, Pacific Institute president emeritus Peter Gleick said, “as SGMA is implemented, I think it's inevitable, we're going to see some ag land come out of production and some agricultural water use reductions. I think it's possible to have a strong, healthy agricultural economy anyway.”

The report relies on state data that estimates urban encroachment to calculate reductions in ag water use. Even though agricultural water use doesn’t have the same energy impacts nor related greenhouse gas emission implications as urban use, Cooley said water management discussions in agricultural areas don’t tend to even consider energy and emissions. The report could only incorporate data from the Central Valley in its rural/ag estimates because the state data the researchers relied upon didn’t include the other 20% of California’s ag lands.

Cooley said maintaining separate ag and urban water use projections ultimately is a disservice to managers working in both areas. She would like to see “some harmonized projections for urban and ag, because the urban suppliers may not be projecting that encroachment” that the ag scenarios count on. She told Agri-Pulse in an interview that long-range forecasting for each geography is dependent on the other.

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Pumping groundwater consumes most of the energy needed for agricultural water use and the report finds that “has become increasingly energy-intensive as groundwater levels have fallen around the state.” As SGMA is implemented, the authors recommend improving pump efficiency, allowing groundwater levels to rise and shifting pumping—and its associated energy use—to times when the electricity comes from renewable sources. Still, the authors caution that estimates of the climate impacts of ag water energy use remain difficult to calculate because of the range of uncertainties including temperature, precipitation and how much ag land will be removed from production. And acres could be temporarily fallowed for some time versus permanently removed from agriculture through development.

The report offers a caveat to its estimates for land that does stay in production: “these scenarios do not account for economic factors, such as crop values on domestic and international markets, federal and state agricultural policies, and other factors that affect farmers’ land use choices.”

While fewer acres in production would, in theory, reduce ag water energy use and therefore its carbon footprint, the authors caution that if pumps have to work harder to reach less accessible water, those climate gains could be reduced. Cooley would like energy use and its greenhouse gas emissions, which will change as the California grid is decarbonized, to be integrated into groundwater management and sustainability planning.

“We talk a lot about SGMA and some of the opportunities and challenges,” Cooley said, “but we haven't really thought about it through an energy lens as much as we could or should.”

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