Rationing not necessary: CA could greatly increase its water supply
Yosemite Falls, Yosemite National Park. Image by Wikimedia Commons
In every other state, options are severely limited by geography and climate. In California, they’re limited by politics. Edward Ring explains in National Review (excerpted and edited for brevity).
California can dramatically increase its usable water supply through investment in new water supply infrastructure. Currently, California’s farmers rely on 30 million acre-feet per year for irrigation, and the state’s cities consume about 7.5 million acre-feet per year. If California realized its unique potential to invest in new water supply projects, with federal help, it would give it the ability to be flexible when asserting its senior water rights on the Colorado River. What follows are ways California, and only California, has the potential to increase its annual water yield by 10 million acre-feet per year. That increase would be enough to cope with a prolonged drought without starving cities or farms of water. It would also be enough for California to agree to generous deals with the other states that need water from the Colorado River.
Thin the Water-Guzzling Overcrowded Forests
Thin the forests on the entire Sacramento–San Joaquin watershed to historically normal levels. The extremely thick tree canopy that results collects snow that evaporates instead of falling to the earth to percolate and recharge the springs that feed mountain streams. The rain and snow that do hit the ground are immediately consumed by the many stressed trees that are competing for an inadequate supply of water, nutrients, and sunlight.
A fascinating 2011 study by experts from UC Merced, UC Berkeley, and the Environmental Defense Fund reported that 60 percent of the water consumed by the state comes in the form of Sierra runoff, and that when forest cover is reduced by 40 percent, total runoff increases by an estimated 9 percent.
Dredge the Silt out of the Delta and Delta Tributaries
Resuming regular dredging operations along at least 75 miles of south delta channels, along with at least 25 miles of delta tributaries where silt has created flood risk, would have two water supply benefits. First, it would allow at least another million acre-feet per year to be retained in California’s reservoirs. As it is, water is released from these reservoirs to reserve flood control capacity for a strong late spring storm or an abrupt melting of the snowpack. But if the maximum rate of flow in the tributaries and delta channels were increased through dredging, it would be safe to fill reservoirs to higher levels. This would be especially beneficial in dry years when the reservoirs are partially emptied and there are no spring storms or significant snowpack. Dredging would also increase the overall volume of water in the delta, meaning that operating the delta pumps would not as readily alter, or even reverse, the flow of fresh water through the delta. Dredging would also benefit salmon, which prefer to migrate in deeper and cooler water, and help them avoid bass, which prefer warm and shallow water.
Rewrite the Rules Governing the Delta Pumps
The pumps situated at the southern end of the Sacramento–San Joaquin Delta — state and federal combined — have the capacity to move more than 900,000 acre-feet of water per month, but they rarely operate at capacity.
Why, during wet years, aren’t we using more pump capacity to take the so-called big gulp? With just modest modifications to the operating restrictions, and using existing pumps, at least another million acre-feet per year can be pumped south from the delta into the state and federal canals.
Build New Infrastructure to Harvest Delta Flows
While the delta tunnel project dominates water policy debates in California, there are other ways to get more water out when storm runoff surges through the delta. The half-built Folsom South Canal diverts water from the American River, a major delta tributary, transporting it 20 miles south to urban and agricultural users along its course. But this canal could be extended another 25 miles to reach the Clifton Court Forebay, where water from the delta already supplies the existing delta pumps. This longer canal could also tap additional delta tributaries. This underused canal has a capacity of 3,500 cubic feet per second, which is 2.5 million acre-feet per year. If it was extended and connected to additional delta tributaries, it could probably deliver another million acre-feet per year to the delta pumps.
There is also a proposal for fish-friendly delta diversions, an example of potentially game-changing infrastructure. It would involve creating a channel in an existing delta island, lining the bottom, and burying perforated pipes underneath a bed of gravel to withdraw fresh water during storms. With no impact to either current or fish, a 200-acre site could yield 15,000 acre-feet per day. Even if it only operated for 100 days per year, during the wettest months, this project could cost-effectively harvest 1.5 million acre-feet per year from the delta.
Expand Reservoir Storage Capacity
The most promising opportunity is to raise the height of the Shasta Dam. An 18-foot increase would increase the storage capacity of this massive, 4.5 million acre-foot reservoir by another 600,000 acre-feet. At an estimated cost of $1.8 billion, this project is California’s most cost-effective potential reservoir upgrade. Having additional cold water available for summertime releases from a deep pool reservoir like Shasta would also improve downstream habitat. Expanding this reservoir, however, is fraught with controversy. All water projects in California attract organized and apoplectic opposition from well-funded environmentalist litigators and lobbyists, and Shasta’s proposed expansion is no exception.
A major storage project with a slightly greater chance of completion is the Sites Reservoir. This proposed 1.5 million acre-foot reservoir would be north of the delta, an off-stream reservoir designed to store water collected and pumped into it from the Sacramento River during high winter flows. At its latest projected construction cost of $4 billion, the Sites Reservoir is the only major reservoir proposal in California that still has official, if tepid, support from the state legislature and water bureaucracies. On the drawing board since the 1950s, and supposedly funded via a voter-approved water bond in 2014, Sites remains mired in litigation, and it is anybody’s guess if it will ever be built.
Expand Underground Storage Capacity
California is blessed with capacious aquifers so vast that the extent of their capacity remains unknown. An expert assessment from Stanford University puts the range between 850 million and 1.3 billion acre-feet. This is a staggering amount of available storage, most of it situated in the San Joaquin Valley south of the delta. It would make a tremendous staging area to store water, not only for the nearly 5 million acres of irrigated farmland in the San Joaquin Valley but also to supply the 25 million Californians who live in the major metropolitan areas of greater Los Angeles and San Diego.
The drawbacks to underground storage are the necessity to identify and avoid (or remediate) contaminated aquifers, the energy required to pump the water back out of storage, and the challenge of managing how much water drawn out of the aquifer goes back to the purchaser that put the water into it. Unlike water contained in a reservoir, water in aquifers drifts, and a percolation basin in one county may end up recharging the wells in an adjacent county. But this is not enough downside to diminish the opportunity.
As it is, farmers throughout the San Joaquin Valley already have distribution canals through which they receive irrigation water allocated each year from the state’s California Aqueduct and the federally operated Delta-Mendota Canal. With their groundwater pumping now restricted because of dangerously depleted aquifers, they have the opportunity to allocate a portion of their acreage to creating percolation basins connected to the existing systems built to receive water from the aqueducts. Then, if more water is withdrawn from the delta through new projects or increased pumping, they can receive water deliveries in winter and store it underground.
Urban Wastewater Reuse, Runoff-Harvesting, and Desalination
A 2022 study by the Pacific Institute concluded that California’s urban “stormwater capture potential is 580,000 AFY [acre-feet per year] in a dry year to as much as 3.0 million AFY in a wet year.” The challenge, of course, is whether engineers can design systems to capture whatever the skies deliver. In Los Angeles, average annual rainfall is only 12 inches per year, but on August 20, 2023, 2.5 inches fell within 24 hours, nearly all of it running into the Los Angeles River. Building the infrastructure to harvest that occasional torrent would be like building a 50-lane freeway to keep traffic moving at the speed limit during an unusually heavy rush hour. It makes no sense. But throughout Los Angeles County and elsewhere, cities are investing in daylighting streams and reducing impermeable surfaces to encourage percolation, in addition to building dedicated percolation basins. It’s making a difference. In the very wet 2022–23 rainy season, L.A. County Public Works estimated that stormwater capture at groundwater recharge facilities totaled over 500,000 acre-feet.
Given the potential of urban runoff-harvesting, wastewater reuse, and desalination, we must not underestimate just how much water supply can be locally generated within California’s densely populated cities. Through a combination of all three of these project types, it is feasible to add another 2 million acre-feet per year, if not more, to California’s total water supply.
While some of these projects may overlap, it is safe to estimate the potential of new water supply projects to deliver the following: forest-thinning, 2 million acre-feet per year; dredging delta channels and tributaries, 1 million acre-feet per year; restructured delta pumping rules and new facilities to safely divert flood runoff from the delta, at least 3 million acre-feet per year; expanded surface storage, 1 million acre-feet per year; runoff-harvesting from Sierra tributaries, 1 million acre-feet per year; urban runoff-harvesting and wastewater reuse and desalination, at least 2 million acre-feet per year.
Read the whole thing here.
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