Lower Twin Lake dam
Lower Twin Lake
Lower Twin Lake is a privately-owned reservoir located in Napa, California, with a primary purpose of water supply. Built in 1985, this Earth dam stands at a height of 18 feet and has a storage capacity of 127 acre-feet. The reservoir covers an area of 12 acres and is fed by Tr Pope Creek, offering recreational opportunities along its shores while also serving irrigation needs in the region.
Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Lower Twin Lake is regulated, permitted, inspected, and enforced to ensure its safe operation. The dam is classified as having a low hazard potential and a fair condition assessment as of September 2017. With a maximum discharge capacity and spillway details not specified, this dam is a vital part of the local water infrastructure, especially in times of drought or water scarcity.
In the event of an emergency, the reservoir's emergency action plan (EAP) status, inundation maps, and risk assessment details are not explicitly mentioned in the available data. Despite this, Lower Twin Lake remains a crucial water resource for the surrounding area, contributing to irrigation, recreation, and overall water supply needs while being overseen by state regulatory agencies for its safe and sustainable operation.
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 Lower Twin Lake -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Napa R Nr St Helena Ca | 13 cfs | → |
| Putah C Nr Guenoc Ca | 45 cfs | → |
| Sonoma Creek A Kenwood Ca | 3 cfs | → |
| Maacama C Nr Kellogg Ca | 21 cfs | → |
| Cache C A Rumsey Ca | 715 cfs | → |
| Napa R Nr Napa Ca | 38 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Lower Twin Lake.
Boat launches
- Chaparral Cove Napa County
- Knoxville Road 1601, Napa County
- Ball Park Avenue 14775, Clearlake
- Napa Valley Vine Trail, Napa
- Island Drive Lake County
- Cuttings Wharf Road 3175-3337, Napa
Campgrounds
- Camp Site 1-35
- Camp Site 36-55
- Camp Site 73-100
- Chaparral Cove - Lake Berryessa - Usbr
- Camp Site 56-72
- Manzanita Canyon - Lake Berryessa - Usbr
Fishing spots
Track Lower Twin Lake 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 Lower Twin Lake
Where does the data for Lower Twin Lake 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 Low 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 Lower Twin Lake.