Yes, there will be water for Sites Reservoir now and in the future

By Sarah June 2, 2023

During the drought, one question seemed to come up often about Sites Reservoir: if you build it, can you fill it?

With California being as dry as it was, the question was a natural one. There didn’t seem to be water anywhere, yet we want to build a new place to store it. We would say that the dry years are exactly why we need to build Sites.

But to help address this fundamental question, the Sites Project Authority conducted the most extensive water availability analysis in California history. Our analyses of a wide range of possible scenarios all showed that there is enough unappropriated water in the Sacramento River and Delta system to fill Sites Reservoir while still fulfilling all existing senior water rights and meeting environmental resource needs.

This is not paper water. This is an extensive and expansive suite of analyses. Our team of experts looked at six water supply scenarios to determine how much water would be available to store in Sites Reservoir under a variety of conditions. These scenarios ranged from historical conditions to climate change projections as far out as 2070.

In every single scenario we found that there were years Sites could fill to capacity at 1.5 million acre-feet. (In fact, more than 1.5 million acre-feet in some years, although we have limited our maximum diversion to this amount). Although the exact amount of available water will vary year to year, the scenarios analyzed show that an annual average of at least 658,000 acre-feet of water would be available for Sites.

2023 provides a great example. This year’s storms would have provided roughly 700,000 acre-feet of water for Sites. That’s about half the capacity of the reservoir collected during just a few months. If we had Sites today, that water would be stored and ready to use for the next dry year.

Some folks have asked is Sites will take all of the remaining unappropriated water in the Sacramento River system. While this is a decision for the State Water Board to make, we don’t believe this to be the case. Based on the Project’s CalSim modeling, Sites would divert a long-term average annual amount of about 300,000 acre-feet.  All of the scenarios analyzed in the Authority’s analysis show that an annual average of at least 658,000 acre-feet of water would be available for Sites. What this tells us is that there is ample water for the Project AND other users. The Project is not taking all the water available in the Sacramento River system. There remains unappropriated water available for other new water right applications that may come after Sites Reservoir.

There are myriad water supply scenarios that will ultimately determine how much water is available for Sites, and anyone else for that matter. But by looking at such a range of conditions, we can safely say that the water is there. There may be years when we are releasing more from Sites than we are putting in—but the times when we can fill Sites, make it worthwhile. Sites is a good investment to helping us balance out the annual variations we see and will continue to see in our climate.

The analysis we’ve issued coincides with a critical milestone for the project. The State Water Resources Control Board had requested that we demonstrate the water is available before accepting our water right application. We have done so, and the application has now been accepted for review by the State Water Board. Over the coming year, we will undergo the extensive review and consideration process for one of the largest new water rights in modern California history.

No one is more invested in ensuring there will be water for Sites than our team and the project participants who represent millions of people, farms, businesses and the environment. They are paying for a water supply asset, and they want to know that water will be there when they need it. We are eager to share the results of this analysis and look forward to a big year ahead for Sites Reservoir. For more information on the Water Availability Analysis, visit