Lower Ansonia Reservoir Dam Dam
Lower Ansonia Reservoir Dam
The Lower Ansonia Reservoir Dam, also known as Lower Derby Hill Reservoir, is a vital structure owned by the local government in East Derby, Connecticut. Built in 1887, this earth dam stands at a height of 17.8 feet and serves the primary purpose of water supply for the area. With a normal storage capacity of 71 acre-feet and a maximum storage of 90 acre-feet, this dam plays a crucial role in regulating water flow and ensuring a stable water supply for the region.
Located on the Naugatuck River Tributary, the Lower Ansonia Reservoir Dam has a surface area of 9.6 acres and a drainage area of 0.56 square miles. Despite its age, the dam is regularly inspected and deemed to be in fair condition with a high hazard potential. The last inspection in August 2015 and a condition assessment in November 2015 indicate that the structure is well-maintained and meets state regulatory standards, with a designated emergency action plan in place for any unforeseen events.
With its historical significance and critical role in water resource management, the Lower Ansonia Reservoir Dam stands as a testament to effective dam engineering and maintenance practices. As a key component of the local water supply infrastructure, this dam plays a vital role in ensuring water security and resilience in the face of climate change challenges. Climate and water resource enthusiasts will appreciate the careful management and monitoring of this important structure to safeguard the surrounding community and environment.
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 Ansonia Reservoir Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Housatonic River At Stevenson | 455 cfs | → |
| Naugatuck River At Beacon Falls | 113 cfs | → |
| Mill R Nr Hamden | 10 cfs | → |
| Rooster River At Fairfield | 4 cfs | → |
| Pootatuck R At Sandy Hook | 15 cfs | → |
| Pomperaug River At Southbury | 28 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Lower Ansonia Reservoir Dam.
Boat launches
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Campgrounds
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Fishing spots
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River runs
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About Lower Ansonia Reservoir Dam
Where does the data for Lower Ansonia 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 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 dam, set a threshold, and you'll get a push the moment conditions cross.
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.