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How the Colorado River’s Future Depends on the Salton Sea

California’s giant desert lake is key to negotiations over the future of Colorado River water supplies. It’s a battle between millions of water users and a complex and troubled ecosystem.

Written by Matt Weiser Published on Read time Approx. 7 minutes
West nile
Birds find refuge at sunset on the surface of the Salton Sea in the Southern California desert in 2002. Millions of birds rely on the Salton Sea for important resting and feeding habitat during their annual migration on the Pacific Flyway.Reed Saxon, Associated Press

California’s largest lake, the Salton Sea, is an accident. It was created in 1905 when a levee broke on an irrigation canal, flooding a giant desert playa. Today it has become a sticking point in negotiations between three states over the future of the Colorado River.

The three states – California, Arizona and Nevada – are in the midst of negotiating a drought contingency plan (DCP). It would commit each state to reducing diversions from the Colorado River in order to prevent Lake Mead from shrinking to disastrously low levels.

California is relying on Imperial Irrigation District to make a significant contribution, because it is the largest single diverter of Colorado River water. But if the district reduces its diversions, that will mean less farm runoff draining into the Salton Sea. This means the sea will shrink, causing a cascade of ecological problems for which the district is partly liable.

To help us understand all this, Water Deeply recently spoke with Michael Cohen, a senior research associate at the Pacific Institute, a water policy think-tank based in Oakland. Cohen specializes in Salton Sea and Colorado River issues.

Water Deeply: Why is the drought contingency plan (DCP) important?

Michael Cohen: The DCP is important because, essentially, the Colorado River is over-allocated. Particularly in the lower basin, they have what’s called a structural deficit: In normal years, 1.2 million acre-feet [1.5 billion cubic meters] more water flows out of Lake Mead than flows in. So Lake Mead drops by roughly 12ft [3.6m] per year.

Given that trajectory, it pretty quickly reaches dead pool, meaning there’s no water left in Mead, which then means no water for Southern California and the Central Arizona Project, and 90 percent of the Las Vegas metro area’s water supply dries up. So you’re talking about 30 million people who depend on Lake Mead. Not to mention 1 million acres [400,000 hectares] of irrigated land. And it’s a major hydropower producer.

Lake Mead is pretty critical to the Southwest generally. They’re trying with the DCP to avert this structural deficit and reduce the amount of water we’re taking out of Mead, to get it closer into balance with actual supply.

Water Deeply: How is the Salton Sea connected to these negotiations?

Cohen: The DCP is connected to the Salton Sea because the plan expects that Imperial Irrigation District (IID) would take less water from the Colorado River. When Lake Mead drops to elevation 1,045, California is expected to reduce its take from the Colorado River, for the first time, by 200,000 acre-feet [250 million cubic meters]. In the most recent DCP terms I saw, Imperial Irrigation District would provide 60 percent of that reduction, so IID would reduce its take of the river by 120,000 acre-feet [150 million cubic meters].

Water Deeply: Can the DCP proceed without Imperial Irrigation District?

Cohen: In theory it could, because the other California parties, the largest being Metropolitan Water District of Southern California, could say they’ll step up and meet California’s obligations. But in practice, Met is less likely to forego that amount of water.

IID has certainly stated they need some assurances on the Salton Sea before they move forward on the DCP. They’re a key player. Without IID, California can’t meet its DCP obligations. A 200,000–350,000 acre-foot [250–430 million cubic meters] reduction is counting on IID participation.

Water Deeply: What effect does this have on the Salton Sea?

A map shows the location of the Salton Sea and the Colorado River Basin. (Image courtesy Central Basin Water District)

Cohen: Somewhere in the order of 85 percent of the water flowing to the Salton Sea comes from the Imperial Valley. Essentially, it’s surface water and tile drainage from farm fields. As IID takes less water from the Colorado River, that means less water flows to the Salton Sea. Because the Salton Sea is a terminal lake, when less water flows in, the Salton Sea shrinks.

So the concern is that, because of the DCP, the Salton Sea would be smaller than it would be otherwise. As the sea shrinks, some of that land is exposed, and dust blows off that land.

Under existing regulations of the local air district, the landowner is responsible for dust that’s emitted off lands in the Imperial Valley. IID is a major landowner, particularly at the southern end of the Salton Sea, and IID is liable for a lot of the dust getting blown off the Salton Sea. So as the sea shrinks, it represents a direct cost to IID. That’s the crux of it.

Under the Quantification Settlement Agreement (QSA) of 2003 (a water transfer from IID to San Diego), there was an agreement that said as the Salton Sea shrinks, essentially the state of California backstops liability or mitigation requirements.

The QSA parties – Imperial Irrigation District, San Diego County Water Authority and Coachella Valley Water District – have met their responsibility to pay into a mitigation fund. But they capped it because they didn’t know what the total cost would be, although they knew it would be huge. So the state of California said, “We will assume liability for costs that exceed the costs these parties agreed to.”

IID has put the state on notice that it hasn’t lived up to its part of the deal, which is to put together a mitigation plan to deal with the Salton Sea as it shrinks. And now there are negotiations over the DCP, which is essentially going to exacerbate the situation.

Water Deeply: Has there been any progress on that state’s mitigation plan?

Cohen: The state came out [in March] with what they’re calling a “draft 10-year plan for the Salton Sea.” The QSA allowed 15 years to come up with a plan, and it said in the interim we’re going to require IID to deliver mitigation water to offset the impacts of the transfer to San Diego.

But this is the 15th year. So at the end of this year, that requirement goes away. And next year, the Salton Sea is going to start dropping very rapidly because it will no longer get that mitigation water from IID. All of a sudden, it’s going to receive 10–15 percent less water. So, essentially, it’s going over a cliff. IID is seeing this and saying, “Hold on, we need to deal with this problem before we move on to the DCP.

The state really needed to do this plan five-plus years ago so these projects were being implemented now.

Water Deeply: Why is it a problem if the Salton Sea shrinks?

Cohen: There are two main challenges. One is that it exposes lakebed, which creates dust, and that’s a major public health threat. The Imperial and Coachella valleys already fail to meet air-quality requirements, and asthma rates are already higher than the state average. So, your baseline is an already-bad air-quality situation, which is going to be exacerbated as the Salton Sea shrinks and more dust blows off that lakebed.

The next concern is that as the Salton Sea shrinks, it gets much saltier and other water-quality parameters also decline. Which means that, first, the fish die off. That’s already started to happen. Then a lot of the food sources for the birds die off.

The Salton Sea now is a major stopover for birds on the Pacific Flyway. A total of 424 bird species have been observed on the Salton Sea so far. And of course, in California there are far fewer wetlands than there were historically. We’ve dried up 90–95 percent of the wetlands in California. So these migratory birds have far fewer places to rest and refuel. The Salton Sea has filled that niche. As water quality continues to degrade, it’s no longer going to be able to provide that function.

Water Deeply: Will the state’s 10-year plan satisfy IID?

Cohen: I think that remains to be seen. IID was not satisfied with the draft they saw last December. But my hope is that California takes those concerns into consideration and redrafts the plan to meet those concerns.

Water Deeply: What are the restoration costs at the Salton Sea?

Cohen: We don’t know what the total cost is because it depends how much is dedicated to water quality versus air quality and how they allocate those costs. Odds are, we’re looking at $1 billion-plus.

But one of the benefits of the Salton Sea is we don’t need to pay for everything at once. Those projects can be phased in over time so you can pay for them over time. You can just build them as the sea recedes and you get benefits as you go.

I’m hopeful that the pieces are starting to line up and we can start to see some progress. I think the governor is paying attention to this, the legislature is paying more attention. It’s a little late, but I think there’s still an opportunity to make a real difference.

In some respects, dramatic change is inevitable at the Salton Sea. Essentially, what we’re going to shift from is a Salton Sea people recognize now to a very different, very managed system. But this managed system can still provide a lot of benefits. It could still be a very functional ecosystem.

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