Cogswell dam
Cogswell
Cogswell Reservoir, located in San Gabriel, California, is a rockfill dam completed in 1935 for the primary purpose of flood risk reduction. With a dam height of 266 feet and a storage capacity of 8,969 acre-feet, Cogswell Reservoir plays a crucial role in managing water resources in the region. Owned and regulated by the local government, the dam is also used for hydroelectric power generation, irrigation, and water supply, highlighting its versatility and importance in the area.
Despite its satisfactory condition assessment and high hazard potential, Cogswell Reservoir undergoes regular inspections and enforcement to ensure its safety and reliability. The dam is state-regulated and permitted, with a history of meeting guidelines and maintaining emergency preparedness. With the Wfk San Gabriel River flowing through its vicinity, Cogswell Reservoir serves as a vital infrastructure for water management and climate resilience in Los Angeles County. As a significant feature in the region's water landscape, Cogswell Reservoir underscores the intersection of water resource management and environmental stewardship.
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 Cogswell -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| San Gabriel R Bl Santa Fe Dam Nr Baldwin Pk Ca | 139 cfs | → |
| Arroyo Seco Nr Pasadena Ca | 6 cfs | → |
| Big Rock C Nr Valyermo Ca | 48 cfs | → |
| Rio Hondo Ab Whittier Narrows Dam Ca | 77 cfs | → |
| San Gabriel R Ab Whittier Narrows Dam Ca | 5 cfs | → |
| Rio Hondo Bl Whittier Narrows Dam Ca | 7 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Cogswell.
Campgrounds
- Glenn Camp
- Glenn Camp Campground (Hike Or Bike In 7 Miles)
- Spring Camp Campground
- Spring Camp
- Devore
- Devils Cyn
Fishing spots
Paddle runs
- Gaging Station Below Spillway Of Cogswell Dam (Ne 1/4, Se 1/4, Sec 19, T2n, R10w) To Confluence With Nf San Gabriel River (Sw 1/4.Sw 1/4, Sec 15, T2n, R9w)
- Cooper Canyon- Near State Highway 2 (Sw 1/4, Ne 1/4, Sec 16, T3n, R10w To Confluence With Little Rock Creek
- North Fork - Confluence Of Soldier And Coldbrook Creeks (Se1/4,Sw1/4, Sec) 5, T2n,,R9w To Conflluence With West Fork Of San Gabriel (Sw 1/4,Sw1/4, Sec 17, T2n, R8w)
- West Fork - Headwaters (Se 1/4, Ne 1/4, Sec 14, T2n, R12w) To Cogswell Reservoir (Ne 1/4, Sw 1/4, Sec 24, T2n, R9w
- Mainstream - Confluence With Cooper Canyon To Confluence Wit South Fork Little Rock Creek
- Mainstream - Headwaters To Confluence With Cooper Canyon
Track Cogswell 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 Cogswell
Where does the data for Cogswell 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 Cogswell.