Henne dam
Henne
Henne, also known as Lake Henne, is a private water resource located in Angwin, California, in Napa County. Built in 1959, this earth dam stands at a height of 49 feet and has a storage capacity of 109 acre-feet, serving primarily for water supply purposes, including irrigation and recreation. The dam sits on Angwin Stream, with a drainage area of 0.91 square miles, providing vital water resources to the surrounding area.
Managed by the California Department of Water Resources (DWR) under the Safety of Dams program, Henne is regulated, inspected, and enforced by the state to ensure its safe operation. With a high hazard potential but a satisfactory condition assessment as of September 2017, this dam plays a crucial role in water management in the region. Although there are no associated structures and limited information on its emergency action plan and risk assessment, Henne remains an essential component of the local water infrastructure.
Located within the Sacramento District and overseen by Congressman Mike Thompson, Henne presents a blend of historical significance and contemporary water resource management. As climate change continues to impact water availability and quality, understanding and maintaining dams like Henne becomes increasingly important for ensuring sustainable water management practices in the face of evolving environmental challenges.
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 Henne -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Napa R Nr St Helena Ca | 15 cfs | → |
| Sonoma Creek A Kenwood Ca | 3 cfs | → |
| Putah C Nr Guenoc Ca | 51 cfs | → |
| Matanzas C A Santa Rosa Ca | 3 cfs | → |
| Maacama C Nr Kellogg Ca | 22 cfs | → |
| Santa Rosa C A Santa Rosa Ca | 20 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Henne.
⚓ Boat launches
- Chaparral Cove Napa County
- Knoxville Road 1601, Napa County
- Napa Valley Vine Trail, Napa
- Cuttings Wharf Road 3175-3337, Napa
- Cuttings Wharf Road 3270, Napa
- Ball Park Avenue 14775, Clearlake
⛺ Campgrounds
- Bothe - Napa Valley State Park
- Napa County Fairgrounds
- Chaparral Cove - Lake Berryessa - Usbr
- Camp Site 36-55
- Camp Site 1-35
- Camp Site 56-72
🎣 Fishing spots
More fishing →Track Henne 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 Henne
Where does the data for Henne 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 Henne.