Poquonnock Reservoir Dam dam
Poquonnock Reservoir Dam
The Poquonnock Reservoir Dam, also known as Groton Reservoir, is a vital water supply structure located in Groton, Connecticut. Built in 1901, this masonry dam stands at a height of 17.5 feet and has a storage capacity of 1,660 acre-feet, serving the community with a normal storage capacity of 921 acre-feet. The dam is situated on the Great Brook river and is regulated by the Connecticut Department of Energy and Environmental Protection (DEEP).
With a surface area of 139 acres and a drainage area of 15.9 square miles, the Poquonnock Reservoir Dam plays a crucial role in managing water resources in the region. The dam has a high hazard potential but is currently in satisfactory condition, as per the last assessment conducted in January 2018. It is inspected every two years to ensure its structural integrity and overall safety for the surrounding area.
Despite not having a spillway type specified, the dam has a spillway width of 209 feet and a maximum discharge capacity of 1,160 cubic feet per second. The primary purpose of the Poquonnock Reservoir Dam is water supply, and it continues to fulfill this role effectively for the residents of Groton and beyond. As a key component of the local water infrastructure, the dam's importance in managing water resources and ensuring water supply reliability cannot be overstated.
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 Poquonnock Reservoir Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Pawcatuck River At Westerly | 302 cfs | → |
| Pendleton Hill Brook Near Clarks Falls | 4 cfs | → |
| Yantic River At Yantic | 90 cfs | → |
| Shetucket River At Taftville | 780 cfs | → |
| East Branch Eightmile River Near North Lyme | 22 cfs | → |
| Eightmile R At North Plain | 18 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Poquonnock Reservoir Dam.
Boat launches
Campgrounds
- Mystic Koa Holiday
- Laurel Lock Camp
- 315 - Burlingham
- Youth Site 2
- Youth Site 1
- Camp Watchaug (Westerly Ymca)
Fishing spots
Track Poquonnock Reservoir Dam 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 Poquonnock Reservoir Dam
Where does the data for Poquonnock Reservoir Dam 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 Poquonnock Reservoir Dam.