Located just over an hour north of Sacramento in Glenn and Colusa counties lies 14,000 acres of grassland, streams and the main canal of the two counties’ shared irrigation district.
It’s the site of the planned Sites Reservoir, which has long been eyed as a possible place to store excess surface water from across California. The project was first proposed in the 1950s, but failed — and was re-proposed several times since then. Now, after roughly 70 years and several iterations, the off-river storage basin west of the Sacramento Valley is being streamlined and moving forward.
In early November, Governor Gavin Newsom announced he’d be pushing the project forward under his streamlined infrastructure plan. Then last week, the Bureau of Reclamation and Sites Project Authority certified its final environmental impact report and was approved to move forward. Project coordinators say construction will begin in 2024, with completion expected in 2030.
CapRadio’s Vicki Gonzalez spoke with Jeffrey Mount, a senior fellow in the Water Policy Center at the Public Policy Institute of California, about what dent the reservoir will make in the state’s water supply.
This interview has been edited for length and clarity.
Interview highlights
Can you describe why this area — about 80 miles north of Sacramento — is prime for a reservoir?
This is not your Folsom-style reservoir. This is an off-channel reservoir. The [Bureau of Reclamation is] going to drown a valley, which is up in the foothills west of the town Maxwell. … That’s the proposal in that they will put a straw in the river — the way we describe it — and draw water out of the river, pump it up into the reservoir and store it there.
Why or how is it different from dams of the past? What is an off-river storage basin?
These are really important to water supply. Everybody has kind of a vision of Folsom Dam or Oroville or Shasta, but [off-river storage basins] turn out to be really important throughout California and we've been using them for years. Let's think of Los Vaqueros for Contra Costa County, the San Luis reservoir you see when you drive south on I-5, Diamond Valley in Los Angeles, all of these are off stream storage reservoirs. They rely on us basically pumping water during times of high flow into them, storing [the water] then saving [it] for use in the dry times, and that's the principle.
So essentially this could capture storm water from the Sacramento River?
The way it's currently set up — and again this all depends on approval from the state Water Resources Control Board — they'll pump water out of the Sacramento River during periods of high flow. I say “high” because it's not necessarily flood flows, but they have a threshold of higher flows when they can actually pump. And then they turn it off when the river drops down to sort of more normal flows.
Given that this has been proposed in many different versions over the last many decades, what is the argument for needing it now, today?
Well, the argument has been the same all along, and this is to deal with dry-year scarcity. That’s the bottom line. … We don't do a very good job of storing water during these wet periods when it has the least environmental impact, and we don't do a particularly great job of managing water during dry periods when it has a very high environmental impact. The concept behind this [project] is to try and soften the scarcity during these dry periods.
… Regardless of whether you're in favor of it or you're opposed to it, there's a lot of exaggeration about what it does and does not accomplish. Conceptually the idea is that you are basically harvesting these flows — like in [wet] years like 2023, where they project they could have put aside 700,000 acre feet [of water.] That's like 70% of a Folsom Reservoir’s worth of water.
What areas will benefit from the Sites Reservoir?
If you go online and you see who's actually bought into the Sites [project], they're a big broad coalition of folks who want a piece of that water pie. It's everything from the federal government to the state government … but also a lot of irrigation districts in the Sacramento Valley. And there is interest in the part of the metropolitan water district in Southern California.
We rely heavily on this amazing conveyance system that we have here in California, which can move water hundreds of miles to various sources and water does flow uphill to money. So there's a lot of money involved in this and they'd like to get out that water. I honestly think this is [going to] affect the Sacramento Valley, the San Joaquin Valley, probably the Bay Area and will also affect Southern California.
Why not make it bigger if the goal is to store water for people across the state?
The limitation always in this is money. I mean you can envision fantastic infrastructure projects, [but] you can't afford them and their environmental impacts, we're just not going to tolerate it as a society. It just gets too expensive to store much larger volumes. That's the key here. There's a lot that depends on how often we get really wet years, because during these dry years like we had in 2020, [2021 and 2022,] they wouldn't have taken a drop of water out of the river. They would in fact have been putting water back into the river to basically move it to various sources.
So it's very different than Folsom in that regard … When you think about it, [the Folsom Reservoir] is a flood control structure or water supply structure and hydropower structure. Sites is nothing like that. It's just a place to stash water off the stream and then let water out in the dry periods.
In terms of pushback, there are environmental groups that have been vocal about being skeptical — and that's on the light end — to being flat out opposed to another major reservoir that's being built in California. Do their arguments have weight?
Well, you cannot build a dam without impact. Period. I mean they all have impact, there's nothing benign about these things. I mean, the last really big off-stream storage [California built] was the one in Southern California, Diamond Valley, and its impacts were pretty low because it was an obscure place up in the mountains.
But the fact is you're diverting water out of the rivers, and that's where the balance really comes — do those diversions out of the river have serious environmental impacts? Now they're going through that whole process right now. They've released their [environmental impact reports] and these are all in review, people are gnashing their teeth about what kinds of impacts there [might] be. I have colleagues on both sides of this issue … so expect that debate to be really, really strong.
