Lake Hennessey reservoir
Lake Hennessey
Lake Hennessey is a freshwater reservoir located in the Napa Valley of California. The lake was named after one of the first settlers in the area, Charles Hennessey. The primary source of the lake's water is the Conn Creek watershed. The lake also receives water from the Rector Creek and Milliken Reservoir. The lake is managed by the Napa County Flood Control and Water Conservation District. The lake's water is used for agricultural purposes, including vineyards and orchards in the Napa Valley. The lake is also used for recreational activities such as fishing and boating. The lake's depth, size, and water quality make it an ideal location for water sports and fishing. The lake's hydrology is characterized by a surface flow and snowpack providers. The surface flow is a result of rainfall and snowmelt, while the snowpack providers are the Sierra Nevada Mountains.
Daily levels at Lake Hennessey
Storage volume, pool elevation, and total release plotted from the operating agency's daily observations.
Storage
acre-ft · code 2
Pool Elevation
ft · code 1
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 Lake Hennessey -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Napa R Nr St Helena Ca | 4 cfs | → |
| Napa R Nr Napa Ca | 5 cfs | → |
| Sonoma Creek A Kenwood Ca | 0 cfs | → |
| Sonoma C A Agua Caliente Ca | 4 cfs | → |
| Nathanson C A Sonoma Ca | 0 cfs | → |
| Putah C Nr Winters Ca | 644 cfs | → |
About Lake Hennessey
Where does the data for Lake Hennessey come from?
Daily storage, pool elevation, and release rates are sourced from USGS, USBR, and USACE monitoring stations. Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
Storage observations are updated daily by the operating agency. The 15-day weather forecast refreshes throughout the day. Snoflo caches and renders the most recent observation -- check the "as of" timestamp on the storage card.
What does the Hazard 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 below 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 reservoir, set a threshold, and you'll get a push the moment conditions cross.