No Delta (Tunnel) Conveyance Without Building Sites Reservoir

  • Posted on 7 March 2022
  • By Caty Wagner
The Department of Water Resources (DWR) is considering letting California’s largest water users build a 1.5 million acre foot, or 20 sq mi, reservoir that would divert much more water from the Sacramento River. At 13,200 acres, Sites Reservoir (formally called the Sites Offstream Storage Reservoir Project) would be one of the largest reservoirs in California and would include new water diversions from the Sacramento River that could also adversely impact the Trinity River. Since the plan includes water storage for the Bureau of Reclamation, the agency that delivers federal water project water to Westlands Water District, the major diverter of Trinity River water, Sites could cause the Sacramento, Shasta, and Trinity Reservoirs to be overdrafted. The Trinity is the largest tributary to the struggling Klamath River and its coldest water source.
Sites Reservoir currently does not propose to divert water only during really wet years and extremely wet periods, but instead plans to divert water in most years, including averaging nearly 100,000 acre feet of water diversions in dry and critically dry years. Sites Reservoir is now estimating that it will yield around 260,000 acre feet of water per year on average, with more water in drier years and less in wet years. But that means that in most future droughts, there will not be a lot of water in storage—and even less once biologically credible bypass flows and environmental protections are required. 
Proponents now estimate that Sites Reservoir will cost $3.9 billion to construct the project, a 30% increase from prior estimates. As a result, water from Sites is likely to cost more than $700 per acre foot on average—and that cost estimate does not include the additional costs to move water through the Delta, to pay to move water down the California Aqueduct and/or other canals, and the costs of water treatment for municipal and industrial users. The Delta tunnel will cost between $16-40 billion on top of the Sites costs, in an era of climate change, where it was just predicted that the Sierra Nevada will not have snow in 25 years.
On February 4, Sierra Club California staff joined Steve Evans of California Wildlife Coalition to see the proposed site of the Sites Reservoir in Colusa County.
Evans began the tour with a stop in Maxwell, CA where we saw an old building that had not been retrofitted for earthquakes. Reservoirs can induce seismicity, or earthquakes, as they had discovered in Oroville in the 1970’s, or with smaller earthquakes induced by Mendocino Reservoir, so buildings like this one in Maxwell may be in danger of collapse due to its close proximity to the reservoir. We passed almond orchards fed by groundwater, which will be kept in production by the reservoir. Some of the districts up here will likely also sell water transfer to water districts further south. 
We stopped at the proposed location of the reservoir’s dam, which also happens to be a significant and non-mitigatable habitat of federally protected golden eagles. As if Mother Nature herself was listening, we saw a bald eagle and a turkey vulture soar in circles above us (don’t worry, we got a video)! The dam site sits atop the Great Central Valley fault line, which is less than a mile from the reservoir’s proposed location, and produced a 6.7 magnitude earthquake in 1892 and again in 1983.
The proposed site of Sites Reservoir, which is currently a green valley with a few horse ranches, would be very large and wide, but relatively shallow, rising to a ridgeline that Evans points out. He tells us about the modeling they use in the environmental review process, which uses averages that don’t consider daily or hourly timesteps, which are critical for salmon spawning habits. California’s climate also likes to go big or go home- we get big droughts and big floods, but not a lot of mild in-betweens, and our wildlife have adapted to these patterns. These models, like much of our water infrastructure, were built in the wet years of the 1960’s and earlier. Evans predicts that Sites may be a “stranded asset”- it may rarely be full with these severe droughts and possibly be “deadpool”- the level of water may be below where pumps and pipes can even reach it. 
Electricity will be generated when water is released from the reservoir, but will be needed to pump water into the reservoir. The amount of electricity needed and produced is unpredictable, but Sites will likely need more than it can produce. Estimates of the greenhouse gasses produced by the needed electricity, combined with the rotting vegetation of the reservoir, will produce as much CO2 as all of the commuter cars in the LA basin for two days.
Significant diversions from the Sacramento River to fill Sites Reservoir could result in substantial impacts to the river’s ecosystem namely: reduced volumes of water and water quality due to the inability to flush out runoff, agriculture waste and municipal waste, increased temperatures, salinity, and harmful algal blooms (HAB). These affect the sensitive, riparian and aquatic habitats. The region where Sites would be built is an area that naturally produces selenium and other metals and potential pollutants. There may be abandoned mercury mines in the reservoir footprint that could release the mineral in warm waters.
Our last stop was to the Sacramento River National Wildlife Refuge which protects threatened and endangered species in riparian habitat. When the river floods, it deposits seeds and sediment so areas can re-vegetate. It erodes banks and deposits the sand downstream, creating new habitats. Sometimes erosion knocks trees into the water, which creates coverage for fish. The Sites diversions could significantly harm the riparian habitat that depends on the flows, including yellow-billed cuckoos, bank swallows, winter-run and spring-run Chinook salmon, steelhead, and others. Shasta Dam already significantly alters diversions, and Sites could take up to 500 cubic feet per second of flows from the river. 
One estimate is that Sites would drown 14,000 acres of grassland, woodland, chaparral, riparian habitat, vernal pools and wetlands (including 19 acres of rare alkali wetlands). 23 endangered or threatened species would be at risk and 56 other endangered species have the potential to be threatened. There are 4 plant species that the California Native Plant species deems of “rare distribution” that will be threatened.
To construct the Delta Conveyance aka Delta tunnel or Peripheral Canal, Metropolitan Water district and the Department of Water Resources must build Sites Reservoir as storage. Yet, in their worded proposals they always declare, they’ll only take water during wet years from the San Joaquin Sacramento Delta, yet apparently the same doesn’t apply to the Sacramento River. They're all connected. Disconnect much? To quote John Muir: “When one tugs at a single thing in nature, he finds it attached to the rest of the world.”
Every example of water infrastructure projects we heard throughout the day reminded us that ultimately, every time we have faced a drought and the state had to choose between agriculture and the environment when cutting back on water, the environment loses every time and yet they still claim that their environmental standards work.
Click here to see footage from each stop on our tour. Click here to join us for our weekly Stop the Delta Tunnel working group meetings.

Caty Wagner is our Southern California Water Organizer and can be reached at

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