San Andreas dam
San Andreas
San Andreas, also known as San Andreas Lake, is a significant water resource located in San Mateo, California. Owned by the local government, this dam serves as a vital water supply infrastructure, completed in 1870 and standing at a height of 107 feet. With a storage capacity of 19,027 acre-feet and a surface area of 550 acres, San Andreas plays a crucial role in providing water to the surrounding area.
Managed and regulated by the California Department of Water Resources (DWR) and Safety of Dams, San Andreas is subject to regular inspections to ensure its safety and maintenance. Despite being classified as having a high hazard potential, the dam is currently in fair condition. The last inspection in December 2020 revealed its compliance with safety standards, with an emergency action plan in place and regular assessments of its risk management measures. With its location on Tr San Mateo Cr and its proximity to the city of San Mateo, San Andreas is a key player in the water infrastructure of the region.
Enthusiasts of water resources and climate will find San Andreas to be a fascinating case study in dam management and water supply infrastructure. With its historical significance, structural design, and regulatory oversight, this dam exemplifies the complex interplay between human engineering and natural resources. As one of the critical elements in California's water supply system, San Andreas stands as a testament to the ongoing efforts to balance water management, safety regulations, and environmental sustainability in the face of changing climate conditions.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
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.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
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.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around San Andreas -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Pilarcitos C Bl Stone Dam Nr Hillsborough Ca | 4 cfs | → |
| San Mateo C Bl Lo Crystal Sp Res Nr San Mateo Ca | 4 cfs | → |
| Pilarcitos C A Half Moon Bay Ca | 10 cfs | → |
| San Francisquito C A Stanford University Ca | 6 cfs | → |
| San Lorenzo C A San Lorenzo Ca | 14 cfs | → |
| San Gregorio C A San Gregorio Ca | 14 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near San Andreas.
Boat launches
- San Andreas Trail San Bruno
- Sawyer Camp Trail San Mateo County
- San Francisco Bay Trail, South San Francisco
- J Hart Clinton Drive San Mateo
- Whidbey Lane Redwood City
- Harding Road San Francisco
Campgrounds
- Dispersed Camping
- Sweetwood Group Camp
- Half Moon Bay State Beach
- Candlestick Rv Park
- Rob Hill Campground
- Aquatic Park Cove
Fishing spots
Paddle runs
- Headwaters To Mouth
- Headwaters To Ends One Quarter Mile South Of Bear Valley Road Bridge Segment 1: Ends 1/4 Mile South Of Bear Valley Road Bridge Segment 2: Caltrans Corporation Yard At Point Reyes Staton.
- Olema Ranch Campground To Caltrans Corporation Yard At Point Reyes Station
- Gold Creek To Three Pools (Opal Creek Run)
More reservoirs
Track San Andreas in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About San Andreas
Where does the data for San Andreas come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High 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 dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of San Andreas.