This page's gauge is the lower river
The Tuolumne rises in Tuolumne Meadows at about 8,600 feet in Yosemite, where the Lyell and Dana forks meet, and ends more than 158 miles later in the San Joaquin, about 10 miles below the Modesto gauge. The gauge on this page, USGS 11289650, sits just below La Grange Dam, at the top of the valley river. It says nothing about the park. Directly above it, Don Pedro Reservoir, the river's largest, is owned by the Modesto and Turlock irrigation districts, and at La Grange about half the river's natural flow is diverted into the Turlock and Modesto main canals to irrigate more than 200,000 acres. What passes the dam is what the gauge reads.
Monthly means since 2010 below La Grange are about 980 cfs in January, 2,660 in April, 560 in July, 320 in September, 370 in October and 270 in November. No shop publishes a range, so the 300 to 1,000 cfs band on this page runs from the September mean to the January mean. On September 24, 2026 it read 179 cfs, and the Modesto gauge downstream read 223.
La Grange Dam to Hickman Bridge: five weeks left
CDFW's 2026 regulations give the lower Tuolumne one calendar and two sets of gear rules, split at Hickman Bridge. Upstream of the bridge, all the way to the foot of La Grange Dam, you may fish from New Year's Day through Halloween with barbless artificial lures and nothing else. Downstream of Hickman Bridge to the San Joaquin, bait is legal over those same dates, but during the spring window that runs from April 1 to the Friday ahead of May's fourth Saturday, bait hooks must fall within set gap sizes. Everywhere below the dam the daily limit is two fin-clipped fish, trout or steelhead, with four in possession; a healed adipose clip marks a hatchery fish, and anything unclipped is released. November and December are closed, which leaves five weeks in the 2026 season.
New gravel below the dam
Below La Grange the river runs in a fixed channel with a narrow floodplain, much reduced by the diversions, through Waterford, Hughson, Empire, Ceres and Modesto. The irrigation districts and the San Francisco Public Utilities Commission are rebuilding salmon spawning habitat in it. The Powerhouse Riffles project, about $4.7 million, adds roughly 25,000 cubic yards of gravel, 4.8 acres of new gravel features and about 2,400 feet of restored channel, plus around 50 pieces of large wood and 80 boulders; in-water work is due to finish in October 2026. It follows the Old La Grange Bridge restoration completed in 2024, and the partners aim for 77 acres of floodplain rearing habitat by 2030. TID has also published a request for a segregation weir to manage fall-run and spring-run Chinook spawning in the lower river. Expect construction crews in the river channel through October.
Hetch Hetchy to the Clavey: the canyon
Between Hetch Hetchy Reservoir and Don Pedro, the Tuolumne runs through a steep foothill canyon. Cherry Creek comes in just below the intake of the Hetch Hetchy Aqueduct, and the free-flowing Clavey joins lower down. CDFW's rule for this stretch, from O'Shaughnessy Dam down to Clavey River Falls, is open all year, artificial lures only, 2 trout a day. The gauge below Early Intake, 11276900, reads this water and was at 62 cfs on September 24, 2026.
Tuolumne Meadows and the forks, under park rules
Inside Yosemite the Park Service rules apply to the Tuolumne and all its tributaries: artificial lures or flies with barbless hooks, rainbows released, brown and brook trout 5 a day with keeping optional, no bait of any kind and no fishing from bridges. At Hetch Hetchy Reservoir every trout is catch-and-release, wading and swimming are prohibited, and no one may fish from the top of the dam.
Sierra Fly Fisher's guide describes the meadow river as the largest sub-alpine meadow in the Sierra, holding native rainbows, brook trout and browns that reach about 14 inches, and best fished with standard dries in sizes 16 to 22. From June into early October the fish key on an evening Pale Morning Dun hatch, with Yellow Sallies and several caddis species around at the same time. The Dana Fork runs beside Highway 120 from Tioga Pass and is mostly browns; the Lyell Fork runs about 10 miles down Lyell Canyon beside the John Muir Trail, with browns low and brook trout toward the headwaters, and rewards stealth more than matching the hatch.