Flooding alfalfa to *save* water?

Alfalfa, east side Phoenix, February 2015, by John Fleck

Alfalfa, east side Phoenix, February 2015, by John Fleck

University of California researchers have a novel idea: what if we dump more water on alfalfa and use that to recharge aquifers?

Over a six-week period in February, March and April, Dahlke oversaw a test in Siskiyou County in which 140 acre-feet of water were applied to 10 acres of alfalfa. That’s well over twice the amount of irrigation water the field typically gets in an entire year.

“It was just pouring into the ground,” Dahlke said.

The water percolated readily into the earth and the groundwater table in the vicinity of the farm rose quickly. Just as important: by June the alfalfa field that had been watered so heavily was just as healthy as a control plot. Alfalfa is known to “drown” if watered very heavily in summer months, but it appears that the winter dormancy of alfalfa is helping the crop to tolerate saturated soils for some time. Field trials near the UC Davis campus have corroborated the Siskiyou County results, Dahlke said, though additional tests in more soil types and warmer climates (e.g. the southern Central Valley) are needed.

The premise: recharge is good if you have the chance, but land set aside exclusively for the purpose is at a premium. But there’s plenty of alfalfa land where you could try this.

One more example of the adaptive capacity offered by the queen of forages.


  1. Thank you for this very informative journal article link! The properties of chemical processing and detoxification are impressive, as well as water table restoration aspects.
    I will be looking for seeds adapted to Northern N.M. weather ans soils!

  2. Back when I knew people heavily involved in groundwater recharge, I was told that effective recharge is a huge pain. Recharge basins silt up quickly, needing constant management, ie raking up the silt and creating paths for the water to flow in. ASR wells also have major challenges.

    It would be very interesting indeed (actually kinda funny) if the appropriate course of action was for Los Angeles and Orange County water agencies that are responsible for groundwater recharge to start growing winter alfalfa on their big recharge basins.

    You should do some interviews. OCWD’s website is here.

  3. Francis –

    My hunch is that this works best in places where there’s already alfalfa being grown in a basin shared with municipal pumpers. I’m thinking especially Central Arizona, where you’ve got 160,00 acres of alfalfa in Maricopa County alone.

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