Hetch Hetchy Reservoir water level
▲ 0.3 points from 79.1% a year ago
Source: waterdata.usgs.gov/monitoring-location/USGS-11275500, accessed October 1, 2026. Updated every 6 hours.
Hetch Hetchy Reservoir is at 79.6% of full pool (3768.9 ft) as of September 29, 2026. Hetch Hetchy Reservoir was last full on July 26, 2026 (95.1% of normal storage). Hetch Hetchy Reservoir is near Yosemite, California. It has restrooms and picnic area, managed by National Park Service. Check current swimming advisories at Yosemite current conditions (National Park Service) before you go.
Hetch Hetchy Reservoir level history
This site counts a reservoir as full on a day its storage is at or above 95% of the dam's normal storage (National Inventory of Dams). Many reservoirs rarely reach 100%, even in wet years, because operators release water for irrigation, power or flood control before they fill, so this site treats 95% as full. Highs and lows are daily readings in the published data, not official records. Source: USGS daily data.
Storage, % of full pool, since 1930
Hetch Hetchy Reservoir is falling: 79.8% full, down 0.9 percentage points since September 27, 2026.
On this same date last year (September 28, 2025), Hetch Hetchy Reservoir was 79.1% full, 0.7 percentage points lower than today's 79.8%.
Weekly averages of the source's daily readings; older years may be monthly or sparser where that is all the source published. Download the charted data (JSON).
Hetch Hetchy Reservoir map
Hetch Hetchy Reservoir is at 37.9477, -119.7879. Open in OpenStreetMap.
The dam
- Hydropower
- Water supply
Sources: nid.sec.usace.army.mil, accessed September 29, 2026
Visiting Hetch Hetchy (Yosemite National Park)
- Restrooms
- Picnic area
- ADA accessible
No developed camping at the reservoir shoreline. Overnight wilderness travel requires a wilderness permit. Day hiking along the reservoir and into adjacent wilderness is the primary overnight-adjacent use.
Pets are not allowed on the dam or on hiking trails.
Good to know:
- Swimming and boating are prohibited to protect the drinking-water supply; public access is prohibited below the high-water mark.
- Vehicles/trailers over 25 feet long or 8 feet wide are not permitted on the narrow Hetch Hetchy Road. No public transit to this area.
- Primary Bay Area water source for about 2.7 million people (NPS). Hiking season is long due to relatively low elevation (~3,900 ft).
Swimming
Designated swim area: Swimming prohibited (drinking-water reservoir).
Water-quality and swimming advisories change without notice. Always check Yosemite current conditions (National Park Service) before you go.
Sources: nps.gov/yose/planyourvisit/hh.htm, accessed September 28, 2026 , nps.gov/yose/planyourvisit/conditions.htm, accessed September 28, 2026
On the water
No campgrounds, boat ramps, or swim spots linked to Hetch Hetchy Reservoir yet.
Common questions
- Hetch Hetchy Reservoir is at 79.6% of full pool (3768.9 ft) as of September 29, 2026.
- Hetch Hetchy Reservoir was last full on July 26, 2026, when it held 95.1% of its normal storage. This site counts a reservoir as full on a day its storage is at or above 95% of the dam's normal storage (National Inventory of Dams). Many reservoirs rarely reach 100%, even in wet years, because operators release water for irrigation, power or flood control before they fill, so this site treats 95% as full. Based on USGS daily data since October 1, 1930.
- In USGS daily data since October 1, 1930, Hetch Hetchy Reservoir's highest storage was 102.4% of normal storage on December 3, 1950. Its lowest after it first filled (May 30, 1938) was 5.1% of normal storage on March 17, 1961. These are the highest and lowest daily readings in the published data, not official records.
- Hetch Hetchy Reservoir is near Yosemite, California (37.9477, -119.7879).
- Local Government operates the dam at Hetch Hetchy Reservoir.
- Hetch Hetchy Reservoir's dam is used for Hydropower, Water supply.
- Hetch Hetchy Road and entrance are open daylight hours only (sunrise to sunset). November-March: road may close or require chains for ice/snow; call 209/372-0200 (1,1) for road conditions. Parking can fill mid-day on weekends. Fees: Yosemite entrance (private vehicle, 7 days) $35, Yosemite entrance (motorcycle, 7 days) $30, Yosemite entrance (per person, walk-in or bike, 7 days) $20.
- Hetch Hetchy Entrance Station, Staffed during daylight entrance hours; maps and passes available.
- Hetch Hetchy Reservoir has designated swimming at: Swimming prohibited (drinking-water reservoir). Check current advisories at Yosemite current conditions (National Park Service) before you go.