Hydrology and Climate Data Sources

Happy Isles webcam
Happy Isles Gaging Station Webcam
of the Merced River at the Happy Isles gaging station (provided by the USGS).

Streamflow Data

Merced River

The Pohono and Happy Isles gages are located on the main stem of the river in Yosemite Valley. The Wawona gage is on the South Fork of the Merced, near the southern boundary of Yosemite National Park. The Briceburg gage is on Bureau of Land Management land, downstream of the park and downstream of the confluence with the South Fork Merced River.

Tuolumne River

The Grand Canyon of the Tuolumne gage is located just upstream of Hetch Hetchy Reservior, while a second gage is located just downstream of O'Shaughnessy Dam. Data are also available at Falls Creek, a tributary that flows into Hetch Hetchy from the north, and at Tuolumne Meadows, in the Yosemite high country.


Weather Data

Access weather data from stations in Yosemite National Park:

Snow Data

  • Compare this season's Sierra Nevada snow water content with the wettest year on record, the driest year on record, the mean value, and last year's value.
  • See snow survey data from the most recent surveys in California. Snow surveys are performed four times per year at 17 courses in Yosemite and many more throughout the West, with records dating back to 1927. Maximum snow depth at one of Yosemite's snow courses was 232.9 inches in 1969; maximum snow water content was 96 inches in 1983. Read the survey's 1953 history in a Yosemite Nature Notes article [600 kb PDF].
  • California Cooperative Snow Survey's real-time data combines data from multiple agencies to monitor seasonal snowpack, forecast snowmelt runoff, and provide a central source of information about snow and water conditions in California. You can also view real-time snow data in the Yosemite area.
  • View a series of snow melt graphics of the 2010 snow cover, which represents a typical snow year.

Yosemite Hydrology Videos

These Yosemite-produced videos explore water-related topics:

Resources and Further Reading


Get Involved: Volunteer in the park's water quality monitoring effort of the Merced River. Help collect water samples that will be tested for nitrate and phosphorous concentrations. Participate 8 am to 5 pm the first Wednesday of every month (except December and February). Call the volunteer office at 209/379-1850 to sign up.

Contact the Park

Mailing Address:

PO Box 577
Yosemite National Park, CA 95389


(209) 372-0200
The public information office is open from 9 am to 5 pm Pacific time (closed for lunch). Once connected, dial 3 then 5. If the ranger is already on the line, you'll be returned to the main menu. If the ranger is not there, you can leave a message and we will return your call.

Contact Us