Blackwater Dam dam
Blackwater Dam
Blackwater Dam, also known as Dry Reservoir, is a gravity-type dam located on the Blackwater River in Webster, New Hampshire. Built in 1941 by the US Army Corps of Engineers, the dam stands at a height of 75 feet and has a maximum storage capacity of 93,400 acre-feet. Its primary purpose is flood risk reduction, with a spillway width of 241 feet to manage water levels during periods of high discharge.
The dam is associated with two other structures and is owned, funded, designed, and regulated by the US Army Corps of Engineers. It has a high hazard potential and is subject to regular inspections and emergency action plans. USACE actively manages dam-related flood risks by monitoring its condition, prioritizing risk-reducing activities, and collaborating with local emergency managers to ensure preparedness and response in case of an emergency.
With a drainage area of 128 square miles and a moderate risk assessment score, Blackwater Dam plays a crucial role in water resource management in Merrimack, New Hampshire. As climate change continues to impact water resource availability and extreme weather events, the dam's role in flood risk reduction and water management becomes increasingly vital for ensuring the safety and resilience of the surrounding communities.
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 Blackwater Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Blackwater River Near Webster | 19 cfs | → |
| Warner River At Davisville | 348 cfs | → |
| Merrimack River At Franklin Junction | 4,850 cfs | → |
| Contoocook R Bl Hopkinton Dam At W Hopkinton | 758 cfs | → |
| Winnipesaukee River At Tilton | 1,610 cfs | → |
| Contoocook River Near Henniker | 580 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Blackwater Dam.
Boat launches
- Merrimack River Boat Launch
- Depot Lane Hopkinton
- Clement Pond Boat Launch
- Contoocook River Boat Launch
- Maple Street Hopkinton
Campgrounds
- Camp Spaulding
- Mile-Away Campground
- Camp Wilmot
- Northstar Campground
- Clark Brook Campsite
- Cardigan Campsites
Paddle runs
- Begins In Franklin To Sewall's Island
- Sewall's Island To Manchester Street Bridge
- Thornton Railroad Bridge To Bridgewater/Bristol Town Line
- Woodstock/Thornton Town Line To Thornton Railroad Bridge
- First Bridge Upstream On Route 100 To Confluence With West River
- Headwaters To Crossing Of Route 100 Near Route 155
Track Blackwater 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 Blackwater Dam
Where does the data for Blackwater 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 Blackwater Dam.