Three Mile Reservoir Dam dam
Three Mile Reservoir Dam
Three Mile Reservoir Dam, located in Keene, New Hampshire, is a concrete buttress dam completed in 1986 with a primary purpose of flood risk reduction along the Beaver Brook. The dam stands at a height of 20 feet and spans a length of 292 feet, providing a storage capacity of 620 acre-feet and a normal storage level of 250 acre-feet. With a surface area of 8.6 acres and a drainage area of 5.4 square miles, the dam has a maximum discharge capacity of 8000 cubic feet per second.
Managed by the NHDES Dam Bureau, the Three Mile Reservoir Dam is state-regulated, inspected, and enforced to ensure its structural integrity and safety. Despite being classified as having a high hazard potential, the dam's condition assessment in 2017 deemed it satisfactory. The Emergency Action Plan (EAP) for the dam is up to date, with the last revision in May 2020. Overall, the risk assessment for the dam is moderate, with a rating of 3 out of 5.
Water resource and climate enthusiasts will find Three Mile Reservoir Dam a significant structure in managing flood risks in the Cheshire County area. Its design, capacity, and regulatory oversight make it an essential component in safeguarding communities and ecosystems along the Beaver Brook watershed. The dam's operational history, inspection records, and emergency preparedness measures demonstrate a commitment to safety and resilience in the face of changing environmental conditions.
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 Three Mile Reservoir Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Otter Brook Below Otter Brook Dam | 12 cfs | → |
| Ashuelot River Below Surry Mt Dam | 259 cfs | → |
| Ashuelot River Above The Branch | 21 cfs | → |
| Ashuelot River Near Gilsum | 126 cfs | → |
| S Br Ashuelot River At Webb | 25 cfs | → |
| Ashuelot River At West Swanzey | 598 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Three Mile Reservoir Dam.
Boat launches
- Surry Mountain Lake
- Chapman Pond Boat Launch
- Wilson Pond Boat Launch
- Bolster Pond Boat Launch
- Center Pond Boat Launch
- Granite Lake Boat Launch
Campgrounds
- Wheelock Park Campground
- Pilgrim Pines Camping Area
- Swanzey Lake Camping Area
- Fox Brook Tent Site
- Mt Monadnock State Park Campground
- Camp Wanocksett
Paddle runs
- First Bridge Upstream On Route 100 To Confluence With West River
- Headwaters To First Bridge Upstream On Route 100
- Headwaters To Confluence With West River (End Of Sherman Road)
- Headwaters To North Of Searsburg Reservoir
- Headwaters To Crossing Of Route 100 Near Route 155
- End Of Kendall Farm Road To Confluence With West River
Track Three Mile 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 Three Mile Reservoir Dam
Where does the data for Three Mile 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 Three Mile Reservoir Dam.