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An explanation of the Tulloch Reservoir draw down, August 10, 2015

On Aug. 7, 2015, the Tri-Dam Project issued an advisory notice of the upcoming need to draw down Tulloch Reservoir as part of a multi-agency plan to lower water temperatures in the Stanislaus River for rainbow trout, which are protected under the federal Endangered Species Act.

The notification to land owners around the lake specified that lowering the reservoir level could begin as early as Aug. 23 and would be coordinated with additional water releases upriver at New Melones Reservoir managed by the U.S. Bureau of Reclamation.

The Tulloch release will be done in accordance with Federal Energy Regulatory Commission licensing regulations that apply to the reservoir.

Here are answers to frequently asked questions about the management of Tulloch Reservoir and the release schedule:

Who owns the water at Tulloch Reservoir?

The Oakdale and South San Joaquin Irrigation Districts own the dam and the powerhouse and have the right to the water stored in the reservoir. They also own Beardsley and Donnells reservoirs further up the Stanislaus River in Tuolumne County. The two districts formed the Tri-Dam Project to manage these assets.  The reservoirs and the water contained behind them serve the interests of the irrigation districts, to be called upon when needed and as needed.

What is different about this year’s draw down schedule?

Tulloch has a regular draw down protocol that occurs every year. The draw down normally starts in mid-September.  This year it MAY start as soon as Aug. 23.  It will NOT start any earlier.  The draw down will take the lake to the same level as 2012-13, the last time Tulloch was lowered to test its spill gates. It will not go lower. 

The only difference this year in reservoir operations over the last 37 years is that the lake is being drawn down early due to temperature issues in the river because we are in the fourth year of a deep and difficult drought.  The same thing occurred in the 1977 drought.  

Check the Tri-Dam Project website at for updates and information on upcoming lake levels after Aug. 23.

Is the residential drinking water of Calaveras County Water District customers threatened?

No. The water district’s intake pipe is at 465 feet above sea level. The reservoir will be lowered to 480 feet. The pipe will remain in the water.

When will Tulloch Reservoir refill?

Tulloch will refill on the same schedule it always does, beginning mid-March 2016. It is imperative to refill Tulloch because the reservoir serves to provide back pressure on generators at New Melones so they can operate and produce electricity.

What has changed since the spring?

In April, Tri-Dam Project officials projected New Melones would have 147,000 acre-feet of water in storage at the end of September. With that number in mind, we anticipated that we would be drawing from the low level outlet and the cold-water pool in New Melones in mid-July to manage fishery temperatures downstream of Goodwin Dam.  Under that initial plan, we did not see a need to pull on Tulloch’s cold-water pool until the New Melones cold-water pool had been exhausted, which we thought would not be until mid-to late September.

Two things affected that projection: Runoff from a couple of May storms and the aggressive conservation efforts of the irrigation districts’ 6,000 farmers (who saved about 100,000 acre-feet). New Melones is now projected to have 269,000 acre-feet at the end of September. That much water in the reservoir prevents the Bureau of Reclamation from operating its low level outlet. It’s a physical problem based on water elevation. That means the Bureau cannot draw upon the cold-water pool behind New Melones.

The situation today requires Tulloch’s cold-water pool to go first until such time as the lake level in New Melones is low enough so the Bureau can draw upon the cold-water pool there.  We will be blending water between the two reservoirs (Melones’ high level outlet and Tulloch’s low level outlet) to lower river temperatures to protect fish. 

Why so much concern about fish?

The irrigation districts must comply with the law. The federal and state Endangered Species Acts — which protect salmon and rainbow trout in the Stanislaus River – are the law. The districts are working with the federal and state governments as they enforce the law to minimize the impacts to our residents.

In California rivers last year, salmon egg loss was substantial due to warm water temperatures in October.  Salmon returns will be reduced  for years to come as a result. OID and SSJID bear a significant portion of the costs to increase salmon and rainbow trout populations in the Stanislaus River. The irrigation districts invest $750,000 to $1 million each year in scientific research to advance our understanding and improve these fisheries. These costs are borne by the districts’ 6,000 customers; not a single dollar comes from those who live around Tulloch Reservoir or enjoy it for recreation.

The districts will continue to protect our water interests on the river to the maximum value of our farming communities.