Grassy Pond Dam dam
Grassy Pond Dam
Grassy Pond Dam, located in Hopkinton, New Hampshire, is a concrete structure with a primary purpose of recreation. Completed in 1920, this dam stands at a height of 8.5 feet and has a storage capacity of 204 acre-feet. With a surface area of 35 acres and a drainage area of 0.9 square miles, Grassy Pond Dam is a key feature of the surrounding landscape.
Managed by the NHDES Dam Bureau, Grassy Pond Dam is state-regulated, with regular inspections and enforcement measures in place. Despite its low hazard potential and fair condition assessment, the dam poses a moderate risk as per the latest evaluation. The spillway, with an uncontrolled type and a width of 40 feet, plays a crucial role in managing water flow and ensuring safety during high discharge events.
Enthusiasts of water resources and climate will find Grassy Pond Dam an intriguing structure, blending historical significance with modern regulatory standards. Its recreational purpose, combined with its environmental impact on the surrounding intermittent stream, makes it a valuable asset for both the local community and the state of New Hampshire.
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 Grassy Pond Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Contoocook R Bl Hopkinton Dam At W Hopkinton | 1,080 cfs | → |
| Warner River At Davisville | 405 cfs | → |
| Contoocook River Near Henniker | 782 cfs | → |
| Blackwater River Near Webster | 19 cfs | → |
| Piscataquog River Bl Everett Dam | 8 cfs | → |
| North Branch River Near Antrim | 61 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Grassy Pond Dam.
Boat launches
- Clement Pond Boat Launch
- French Pond Boat Launch
- Upper Pond Boat Launch
- Maple Street Hopkinton
- Depot Lane Hopkinton
- Hopkinton
Campgrounds
Paddle runs
- Sewall's Island To Manchester Street Bridge
- Begins In Franklin To Sewall's Island
- Thornton Railroad Bridge To Bridgewater/Bristol Town Line
- First Bridge Upstream On Route 100 To Confluence With West River
- Headwaters To First Bridge Upstream On Route 100
- Woodstock/Thornton Town Line To Thornton Railroad Bridge
Track Grassy Pond 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 Grassy Pond Dam
Where does the data for Grassy Pond 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 Low 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 Grassy Pond Dam.