Letting the Water Loose Again
It seems that the more we learn about water in California, the more we are forced to realize we may have gone too far. That is, too far in trying to develop and harness every trickle.
California’s groundwater exists because many parts of the state, especially the Central Valley, were once floodplain. Storms would sweep in off the Pacific Ocean, rivers would swell with the runoff and that water would flood valleys and marshes. Then the water would slowly trickle into groundwater aquifers, creating the resource that is now about 40 percent of California’s total freshwater supply (more in drought years like this one).
That process doesn’t happen much anymore, because Californians eliminated 95 percent of the state’s wetlands to create cities and farms, and rivers were rerouted into narrow channels. We’re tapping groundwater at an alarming rate, and we’re really not refilling it at all.
Now researchers at UC Davis are showing us it’s possible to put water back in the ground simply by changing how some crops are irrigated. In short, crops like alfalfa can be grown as if they were in a floodplain, by saturating them with water. The plants will take what they need, and the rest will trickle down into the aquifer.
The field produced more weeds than usual, but otherwise the alfalfa crop suffered no ill effects.
“It was amazing to see how well the land absorbed the water and how quickly the water table rose,” said Jim Morris, manager of the Bryan-Morris Ranch in Sikiyou County, where the experiment was conducted this spring. “That’s good news for farming and the environment.”
Other UC researchers have determined that as much as 3.6 million acres of California land may be suitable for this so-called “on-farm recharge” of groundwater, based on soil type and the crops grown there. Not all crops are suitable, either because they can’t grow in flooded conditions or because chemicals used in their cultivation could contaminate groundwater.
The authors of that study estimate a groundwater recharge potential of 1.2 million acre-feet per day. Obviously there won’t be enough water available in many years to flood fields to that degree. But in wet winters, when California experiences excessive rainfall that can cause urban flood damages, routing the flow to farms in this way could be an excellent way to recharge groundwater — just like nature handled it before we showed up.
Bakersfield Aquifers Losing Capacity
In other groundwater news, wells that serve the city of Bakersfield are losing storage capacity as water is pumped out to meet demand during the drought.
Bakersfield, population 363,000, is California’s ninth-largest city.
As water is pumped, soil layers in the aquifer collapse. It’s not reversible, and becomes a permanent loss of water storage capacity in the underground aquifer.
“You know once it starts to settle, you can’t get that space back,” said Rudy Valles, a spokesman for Cal Water, the private water company that operates the wells and serves a significant share of the Bakersfield population.
What this means, in short, is that the next drought will be worse, because the wells will have less reserve capacity to meet demand in the future.
Bay Area Region Moves to Recycle Wastewater
A significant portion of the San Francisco Bay Area has agreed collectively to pursue wastewater recycling as a future drinking water supply.
At a meeting on Aug. 22, members of the so-called Water Policy Roundtable voted to pursue indirect potable reuse.
This is the same method that has been used successfully for years by the Orange County Water District: Treated sewage is recycled through reverse osmosis (the method used to desalinate seawater), then injected into wells to recharge groundwater aquifers. It is later pumped out and processed through the usual drinking water treatment process before delivery to customers.
Members of the roundtable include the City of Livermore, Dublin San Ramon Services District, Zone 7 Water Agency and California Water. All will present the proposal to their respective governing bodies for approval in September.
The members will also launch a polling and education campaign to gauge ratepayer acceptance of the proposal. This will be led by the city of Pleasanton.
Top image: Orchards of walnuts like this one could be excessively flood irrigated to recharge groundwater aquifers when sufficient water is available. ( Josh Viers, UC Merced)