Rivermatics

4 USGS Streamgages · New York Slough system

Tuolumne River flows and levels

Tuolumne River is gauged at 4 USGS streamgages in California, each tracked by Rivermatics. The mainstem runs about 161 miles (259 km) from headwaters to outlet. It drains into the New York Slough system. Drainage area at the gauges ranges from 457 square miles at Tuolumne River near Hetch Hetchy, CA up to 1,538 at Tuolumne River below Lagrange Dam near Lagrange, CA. The gauged reach falls about 3,280 feet, from 3,452 feet down to 173. Rivermatics issues a daily machine-learned 14-day flow outlook for every one of them.

Gauges on this river, upstream to downstream

Ordered by drainage area, which is how far down the river each gauge sits. April and July figures are long-term median daily flows for that month from the USGS record — historical normals, not a forecast and not today's reading.

USGS streamgages on this river, ordered upstream to downstream
Gauge State Drainage sq mi Elevation ft April p50 cfs July p50 cfs Forecast
Tuolumne River near Hetch Hetchy, CA CA 457 3,452 112 133.8 14-day
Tuolumne River Ab Early Intake near Mather, CA CA 484 2,406 156.9 140.7 14-day
Tuolumne River below Early Intake near Mather, CA CA 487 2,221 508 180.4 14-day
Tuolumne River below Lagrange Dam near Lagrange, CA CA 1,538 173 550.9 107 14-day

Typical flow by month at Tuolumne River below Lagrange Dam near Lagrange, CA

The furthest-downstream gauge on this river, so the fullest flow it carries here. Long-term daily discharge percentiles from the USGS record (up to 56 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 126.3 329.6 4,195.2
February 118.6 365.5 5,211
March 138.2 362.4 6,256.5
April 112.9 550.9 7,240
May 12.9 429.5 6,988.1
June 12.6 113.8 4,503.7
July 12.5 107 1,550
August 13.2 101.3 1,139.8
September 10.9 106.2 1,280.1
October 94.5 287.1 1,302.2
November 156.2 256.2 705.3
December 142.2 286.5 2,266.8

All values in cubic feet per second (cfs).

Common questions

When does the Tuolumne River run highest?
April, on the long-term record at Tuolumne River below Lagrange Dam near Lagrange, CA — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 550.9 cfs that month, against 101.3 cfs in August, the lowest. Upstream gauges peak on their own schedule; the table on this page gives April and July for each.
How many gauges are on the Tuolumne River?
Rivermatics tracks 4 USGS streamgages on the Tuolumne River, across California. Each has its own page with the site's full flow record and monthly normals. The river may carry other gauges that publish neither daily values nor discharge statistics; those are not tracked here.
Is there a flow forecast for the Tuolumne River?
Yes, at 4 of the 4 gauges. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on each basin's observed flows, weather and snowpack, and issues a daily outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on each gauge's live screen.
What river system is the Tuolumne River part of?
The Tuolumne River drains into the New York Slough system — it is a tributary somewhere in that chain, following the flowpath down to its terminal river. Rivermatics builds this from the USGS/geoconnex reference-mainstem network rather than from names.
Can I use Tuolumne River data for flood or safety decisions?
No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Other rivers in the New York Slough system

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