A proposed new reservoir in the western Sacramento Valley isn’t supposed to affect Trinity River fisheries, but river advocates say they’ve found the devil in the details.

The Sites Reservoir planned by the state in Colusa and Glenn counties is pitched as a means of catching and storing excess water from major storms. Located off-stream, water from the Sacramento River would be pumped to the new reservoir.

About half of the Trinity River’s water is diverted to the Sacramento River each year for Central Valley Project uses. However, under the Trinity River Record of Decision, a set amount of water is also released to the river each year based on water year type.

The draft Environmental Impact Report/Statement for the project indicates that it poses no significant impacts on water quality to the Trinity River.

Opponents of the plan disagree, saying the trouble is with changes to the timing of water diversions.

Tom Stokely, a former Trinity County Natural Resources planner who is now a board member for Save California Salmon, said the project has “significant impact to the Trinity River that was not disclosed.”

The Pacific Coast Federation of Fishermen’s Association and Save California Salmon have been sharing what they found out about the project after a hydrologist with experience modeling studies related to operations of Trinity and Lewiston reservoirs reviewed the draft environmental report.

Hydrologist Greg Kamman debates the EIR’s conclusions regarding impacts to the Trinity River.

Kamman concluded that the revised Trinity River Division water operations associated with the Sites Project will lead to increased water temperatures in Lewiston Reservoir during critical time periods in dry years, which in turn will cause releases of water to the Trinity River to be warmer.

Kamman said this is due to a general pattern seen in the data shifting operations in dry and critically dry years so the rate of diversions is increased through the winter months (December-March) and reduced through the summer/fall months (July-November). The latter will slow the flow of water through Lewiston Reservoir, allowing it to warm up more.

Increased river water temperatures in the fall are especially a concern, he said, noting that October is a time when meeting downstream temperature objectives is already compromised.

Any increase in temperature of water released to the Trinity River would increase the potential for violations of objectives established under the Trinity River Record of Decision to protect out-migrating juvenile salmon, Kamman wrote.

The evaluation in the environmental study doesn’t take these temperature changes into account.

Further, Kamman notes that the environmental study doesn’t include in its analysis the 50,000 acre-feet of water to be released each year for Humboldt County and downstream water users.

The Humboldt County Board of Supervisors has supported the project if it doesn’t harm the Trinity River, but will soon consider calls to withdraw that conditional support.

Trinity County so far hasn’t weighed in on the Sites project, but its Trinity County Fish and Game Advisory Commission is drafting a letter recommending that the Board of Supervisors here get involved.

The Sites Reservoir potential impact on the Trinity River was raised at the last meeting of the advisory commission by member Richard Cole of Lewiston.

It was noted that under the Record of Decision, the total volume of river flows is set depending on what year type. However, there was agreement by fisheries experts on the commission that Trinity Lake levels could be drawn down in a way that could affect river temperatures in dry years.

The advisory committee unanimously voted to draft a letter asking the supervisors to join others in requesting that a new Environmental Impact Report be completed which considers impacts to the Trinity River.

Stokely, from Save California Salmon, said he’ll recommend to the Humboldt and Trinity County supervisors that they request a water right condition be placed on the water rights application for Sites that no Trinity River water be used to fill the Sites Reservoir unless the Trinity River Division is making Safety of Dams releases and Shasta Lake is making flood control releases at the time.

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