Reservoir Report

Hetch Hetchy Res A Hetch Hetchy Ca reservoir

California, USA USGS
Today high
--
Tonight low
--
Current storage
3,802ft
% of normal
1%
Loading current conditions…
Right now · current storage
Hetch Hetchy Res A Hetch Hetchy Ca
USGS · 11275500
3,802 ft
As of 2026-05-12
Seasonal avg
3,771
Record max
3,807
24h change
0.0%
Loading storage history…
Loading next 24 hours…
Loading 7-day outlook…
Hetch Hetchy Res A Hetch Hetchy Ca -- None reservoir
Hetch Hetchy Res A Hetch Hetchy Ca None
About this reservoir

Hetch Hetchy Res A Hetch Hetchy Ca

Hetch Hetchy Reservoir, located in California's Yosemite National Park, is a crucial source of water for the San Francisco Bay Area. The reservoir was created in 1923 when the O'Shaughnessy Dam was built across the Tuolumne River. The hydrology of the area is primarily influenced by the Sierra Nevada Mountains and the Pacific Ocean, which provide a reliable and consistent snowpack that feeds the water supply. The Hetch Hetchy Reservoir is fed by the Tuolumne River and also receives water from the Cherry Creek and Falls Creek watersheds. The water from the reservoir provides drinking water to over 2.6 million people and supports agricultural and recreational activities. Despite controversy over the dam's construction, the Hetch Hetchy Reservoir has become an essential resource for California's Bay Area.

StateNone
OperatorUSGS
Site ID11275500
Percent of normal1%
Last updated2026-05-12
Records since2007
Storage trends

Daily levels at Hetch Hetchy Res A Hetch Hetchy Ca

Storage volume, pool elevation, and total release plotted from the operating agency's daily observations.

Reservoir storage, acre-ft

ac-ft · code 00054

Lake or reservoir water surface elevation above NGVD 1929, ft

ft · code 62614

Detailed forecast

Plan around the weather

Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.

Hourly detail

Next 5 days, hour by hour

Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.

Loading hourly forecast…
Deep dive

5-day forecast table

Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.

TimeConditionTemp (°F)Snow (in)Rain (in)Humidity (%)Wind (mps)Wind dir
Loading detailed forecast…
Long-term outlook

15-day temperature & precipitation

Daily temperatures, snow, and rain projected over the next two weeks.

Loading 15-day outlook…
Regional inflow

Nearby streamflow gauges

USGS streamgauges around Hetch Hetchy Res A Hetch Hetchy Ca -- inflows here typically show up in storage 24-72 hours later.

Track Hetch Hetchy Res A Hetch Hetchy Ca in the Snoflo app

Save this reservoir as a favorite and set push alerts when storage crosses a threshold (e.g. "alert me at 80% of normal").

FAQ

About Hetch Hetchy Res A Hetch Hetchy Ca

Where does the data for Hetch Hetchy Res A Hetch Hetchy Ca come from?

Daily storage, pool elevation, and release rates are sourced from USGS, USBR, and USACE monitoring stations. Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.

How often is the report updated?

Storage observations are updated daily by the operating agency. The 15-day weather forecast refreshes throughout the day. Snoflo caches and renders the most recent observation -- check the "as of" timestamp on the storage card.

What does the Hazard hazard rating mean?

The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.

What's "% of normal"?

The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).

Can I get alerts when storage crosses a threshold?

Yes -- alerts are managed in the Snoflo iOS app. Favorite this reservoir, set a threshold, and you'll get a push the moment conditions cross.

More reservoirs

Other water bodies near here

Snoflo-tracked reservoirs and dams within driving distance of Hetch Hetchy Res A Hetch Hetchy Ca.

Premium feature

Favorites and alerts are part of Snoflo Premium. Save reservoirs, set storage thresholds, and get push notifications when conditions cross.

Upgrade to Premium Not now
🔔

Manage alerts in the Snoflo app

Custom alerts are configured in the iOS app -- favorite this reservoir, set a threshold, and you'll get a push the moment conditions cross.

Open App Store