Cheshire Mills Forebay Dam Dam
Cheshire Mills Forebay Dam
Cheshire Mills Forebay Dam, located in Harrisville, New Hampshire, is a historic structure built in 1886 primarily for hydroelectric purposes on the Nubanusit Brook. This concrete dam stands at a height of 29 feet and has a length of 94 feet, with a storage capacity of 1.8 billion gallons of water. The dam is under state regulation by the NHDES Dam Bureau and is subject to regular inspections to ensure its safety and integrity.
With a high hazard potential and a moderate risk assessment score of 3, Cheshire Mills Forebay Dam plays a crucial role in water resource management in Cheshire County, New Hampshire. The dam's uncontrolled spillway, with a width of 38 feet, is designed to handle a maximum discharge of 635 cubic feet per second. Despite being labeled as "Not Rated" in terms of condition assessment, the dam is closely monitored and maintained to prevent any potential risks or emergencies that may arise.
As a key feature in the region's hydroelectric infrastructure, Cheshire Mills Forebay Dam serves as a reminder of the importance of sustainable water resource management and climate resilience. With its long history and significant storage capacity, the dam continues to play a vital role in meeting the energy needs of the local community while also posing challenges that must be addressed through proactive risk management measures and ongoing regulatory oversight.
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 Cheshire Mills Forebay Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Nubanusit Bk Blw Macdowell Dam Nr Peterborough Nh | 31 cfs | → |
| Otter Brook Below Otter Brook Dam | 12 cfs | → |
| S Br Ashuelot River At Webb | 25 cfs | → |
| Contoocook River At Peterborough | 14 cfs | → |
| Ashuelot River Above The Branch | 21 cfs | → |
| Ashuelot River Near Gilsum | 14 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Cheshire Mills Forebay Dam.
Boat launches
See all →
Campgrounds
See all →
Fishing spots
See all →
River runs
See all →
More reservoirs
See all →
About Cheshire Mills Forebay Dam
Where does the data for Cheshire Mills Forebay 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.