Mammoth Reservoir dam
Mammoth Reservoir
Mammoth Reservoir, located in Loomis, California, is a local government-owned water resource primarily used for hydroelectric power generation and irrigation purposes. Built in 1851, this offstream earth dam stands at a height of 23 feet and has a capacity of 103 acre-feet. With a surface area of 11 acres and a drainage area of 0.02 square miles, the reservoir serves as a crucial water management structure in the region.
Managed by the California Department of Water Resources, Mammoth Reservoir has a high hazard potential but is deemed to be in satisfactory condition following a recent assessment in September 2017. The dam is subject to regular inspections, with the last one conducted in February 2021. Despite its age, Mammoth Reservoir continues to play a vital role in water supply and energy production in the area, showcasing the resilience and importance of historical water infrastructure in the face of changing climate conditions.
As a key component of the local water infrastructure, Mammoth Reservoir reflects the intersection of history, hydroelectric power, and water management in California. With its long-standing presence and continued functionality, the reservoir stands as a testament to the enduring value of water resources in the region. Climate enthusiasts and water resource professionals alike can appreciate the significance of Mammoth Reservoir in sustaining the needs of both the community and the environment in an ever-changing climate landscape.
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 Mammoth Reservoir -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Nf American R A North Fork Dam Ca | 422 cfs | → |
| Dry C A Vernon St Bridge A Roseville Ca | 159 cfs | → |
| American R A Fair Oaks Ca | 1,920 cfs | → |
| Deer C Nr Cameron Park Ca | 8 cfs | → |
| Arcade C Nr Del Paso Heights Ca | · | → |
| Bear R Nr Wheatland Ca | 36 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mammoth Reservoir.
Boat launches
- Rattlesnake Road Placer County
- Oak Hill Road 7935, Pilot Hill
- Oaks Nature Trail El Dorado County
- Park Road, Granite Bay
- Green Valley Road 661, El Dorado Hills
- Lake Natoma Northern Boat Ramp
Campgrounds
Fishing spots
- Folsom Lake
- Pg&E Rock Creek Lake Fishing Access
- Lake Clementine
- Natoma Lake
- Lake Combie
- Lake Of The Pines
Track Mammoth Reservoir 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 Mammoth Reservoir
Where does the data for Mammoth Reservoir 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 Mammoth Reservoir.