Tulloch Reservoir Water Level
Tulloch Reservoir is at 496.11 ft today (Oct 30), 13.89 ft below its 510 ft full pool, down 1.26 ft this week.
California · Stanislaus River
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Water level history
About Tulloch Reservoir
Tulloch Reservoir is a reservoir on the Stanislaus River in California, operated by Tri-Dam Project. Its full summer pool sits at 510 ft above sea level. Live water levels come from the U.S. Army Corps of Engineers (CWMS) and update hourly.
Understanding Tulloch Reservoir's water level
Tulloch Reservoir is the regulating pool between New Melones and the irrigation canals of the Oakdale and South San Joaquin irrigation districts. Water released from New Melones, the Bureau of Reclamation reservoir immediately upstream, is re-regulated at Tulloch before it is either diverted at Goodwin Dam just downstream or sent on down the lower Stanislaus River. Goodwin is where the two districts pull Stanislaus water into their main canals, and under a 1988 agreement Reclamation releases up to 600,000 acre-feet a year for diversion there. The districts own Tulloch jointly as part of the Tri-Dam Project, which also includes Donnells and Beardsley reservoirs on the Stanislaus, and govern it through a joint board. The dam is about 200 feet high and 1,600 feet long, went into service in 1958, and holds roughly 67,000 acre-feet. Releases are generally kept low enough that flows downstream stay under about 1,250 to 1,500 cubic feet per second, because higher flows seep into the farmland along the river.
For most of the year Tulloch moves within a band of a few feet. Full pool is 510 feet, the normal maximum water surface, where the lake covers about 1,260 acres. From late May through mid September the target range runs about 506.5 to 509.5 feet. Then comes the fall drawdown, scheduled by the Bureau of Reclamation to meet Army Corps of Engineers flood control requirements. In a normal year the pool steps down a little over a foot a week from mid September to late October and then sits in a winter range of 498.6 to 501.6 feet until the spring fill in late March. That leaves roughly ten feet between a summer high and a winter low. Large local inflows during storms can push the level outside those ranges for a few days, and the schedules say so. Once flood season ends, flood control rules no longer apply and Reclamation can hold extra inflow rather than pass it through.
The shoreline is what sets Tulloch apart. It runs about 31 miles through Calaveras and Tuolumne counties, roughly 60 percent of the land around the lake is privately owned, and about 670 private residential docks line the water. Because Tulloch is a FERC licensed hydropower project (P-2067, licensed in 2006 through 2046), Tri-Dam must permit every dock and structure at or below the 515 foot contour, five feet above full pool, under a Shoreline Management Plan it reviews every ten years. The big exception to the narrow band is the inspection drawdown. Tri-Dam says state rules for cycling and inspecting the dam's gates changed from every five years to every three. For winter 2020 to 2021 the lake went down to 475 to 478 feet, was held there January 4 to 9 for state and federal inspectors, and refilled about 0.6 foot a day until March 22. Another is under way this season, with the low point scheduled for December 30, 2026 through February 1, 2027.
Tulloch Reservoir — frequently asked
What is Tulloch Reservoir's full pool elevation?
510 feet, the normal maximum water surface elevation. At that level the lake covers about 1,260 acres and gross storage is 66,968 acre-feet. The FERC project boundary follows the 515 foot contour, five feet higher, and every dock or shoreline structure at or below 515 feet needs a Tri-Dam permit. In practice the summer target tops out around 509.5 feet, so readings just under 510 are a full lake.
Why is Tulloch so low this fall and winter?
The 2026 to 2027 schedule is an inspection drawdown. Instead of stopping near 500 feet, the lake drops about two feet a week from mid September: 501 to 504 feet in early October, 491 to 494 by mid November, and 475 to 478 feet from December 30 to February 1, 2027, so required inspections and testing can be done in January.
When does Tulloch refill?
After the 2026 to 2027 inspection drawdown, refill starts in early February and climbs about four feet a week: 479 to 482 feet the week of February 2, 491 to 494 by late February, and the normal winter range of 498.6 to 501.6 feet by March 9 to 19. In ordinary years the lake stays in that winter range until late March, then rises to the summer range of roughly 506.5 to 509.5 feet by late May.
Why did Tulloch drop to about 476 feet in 2021?
That was a scheduled drawdown, not a data error. Tri-Dam lowered the lake from September 30, 2020 to January 3, 2021, aiming for 475 to 478 feet, after state rules shortened the cycle for exercising and inspecting the dam's gates from five years to three. The pool was held at the minimum January 4 to 9 for state and federal inspectors, then refilled about 0.6 foot a day in coordination with Reclamation through March 22.
Does Tulloch get drawn down during droughts?
It has been. In the 2015 drought the districts planned an early drawdown to 480 feet to help lower water temperatures in the Stanislaus River for trout protected under the Endangered Species Act, starting no earlier than August 23 instead of the usual mid September. Tri-Dam said it was the only change in reservoir operations in 37 years, with a similar early drawdown in the 1977 drought. The Calaveras County Water District intake at 465 feet stayed underwater.
Who operates Tulloch Reservoir?
The Oakdale and South San Joaquin irrigation districts own it together as part of the Tri-Dam Project, and since 1982 have run their shared power facilities through the Tri-Dam Power Authority. The Bureau of Reclamation issues the elevation schedules, since Tulloch re-regulates releases from its New Melones Reservoir. FERC licenses the hydropower project, whose powerhouse uses vertical Francis turbines, under a license issued in 2006 that runs to December 2046.
Where does water leaving Tulloch go?
A short way downstream it reaches Goodwin Dam, where Oakdale and South San Joaquin irrigation districts divert Stanislaus River water into their main canals. Goodwin was raised seven feet, to 87 feet, to form a small afterbay that smooths out Tulloch's discharge. Water not diverted continues down the lower Stanislaus, where releases are generally kept under 1,250 to 1,500 cubic feet per second because of seepage onto adjacent farmland.
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