Conn Creek dam
Conn Creek
In the heart of Napa, California, lies Conn Creek, also known as Lake Hennessey, a water supply reservoir built in 1946 and managed by the local government. This Earth-type dam stands at 125 feet high and has a storage capacity of 31,000 acre-feet, serving primarily for irrigation and water supply purposes. With a surface area of 790 acres and a drainage area of 54 square miles, Conn Creek plays a vital role in supporting the agricultural and residential needs of the region.
Despite its age, Conn Creek has undergone regular state inspections and enforcement to ensure its safety and functionality. The dam's hazard potential is classified as high, but its condition assessment rates as fair, with the last inspection conducted in December 2020. Located in the picturesque city of Rutherford, this reservoir offers a serene escape for water resource and climate enthusiasts, showcasing the intersection of human ingenuity and natural beauty in water management.
As a key component of the Sacramento District, Conn Creek highlights the importance of sustainable water resource management in the face of climate change challenges. Its strategic location, coupled with its historical significance and ongoing regulatory oversight, underscores the critical role that dams like Conn Creek play in preserving and enhancing water security for communities in California. Explore Conn Creek to witness firsthand the harmonious blend of environmental stewardship and engineering excellence in water infrastructure.
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 Conn Creek -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Napa R Nr St Helena Ca | 8 cfs | → |
| Napa R Nr Napa Ca | 27 cfs | → |
| Sonoma Creek A Kenwood Ca | 2 cfs | → |
| Sonoma C A Agua Caliente Ca | 10 cfs | → |
| Nathanson C A Sonoma Ca | 0 cfs | → |
| Putah C Nr Winters Ca | 548 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Conn Creek.
Boat launches
- Knoxville Road 1601, Napa County
- Chaparral Cove Napa County
- Napa Valley Vine Trail, Napa
- Cuttings Wharf Road 3175-3337, Napa
- Cuttings Wharf Road 3270, Napa
- North Camino Alto Vallejo
Campgrounds
- Spanish Flat Camp Site Office
- Spanish Flat Camp Site
- Foothill Pines - Lake Berryessa - Usbr
- Sugarloaf Ridge State Park
- Lupine Shores Camp Site
- Lupine Shores - Lake Berryessa - Usbr
Fishing spots
- Lake Berryessa
- Berryessa Lake
- Lake Ralphine
- 9th Street Boat Ramp
- City Of Benicia Fishing Pier
- Bodega Harbor
Paddle runs
- Cache Creek
- Olema Ranch Campground To Caltrans Corporation Yard At Point Reyes Station
- 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.
More reservoirs
Track Conn Creek 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 Conn Creek
Where does the data for Conn Creek 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 Conn Creek.