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Flooding alfalfa fields to recharge aquifers

When the rains return to California and the Southwest, and they will, a promising way to recharge aquifers is by deliberately flooding alfalfa fields, as well as fallow fields.

Deliberately recharging groundwater allows aquifers to be managed more like surface reservoirs, and has the potential to increase the state’s water storage capacity by millions of acre-feet. During periods like the current drought, there’s little or no extra water available for groundwater recharge. But in wet years, it may be possible to devote substantial volumes to replenishing 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

John Fleck adds:

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.

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.

Let’s hope the coming El Nino dumps enough water so farmland can be flooded and aquifers recharged. Given the complexity of water law, any water used for this shouldn’t count against someone’s allocation.

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