Blackwater Dam in Webster and Salisbury, New Hampshire is located in the upper Merrimack River Basin. This is a multi-purpose project built and maintained by the U.S. Army Corps of Engineers (USACE) New England District. The dam was authorized by Congress as part of the Flood Control Act of 1938 and as amended by acts in 1941 and 1944 and the Merrimack River Flood Control Compact of 1957. Construction of Blackwater Dam started in 1940 and was completed in 1941, at a cost of $1,300,000. The project consists of an earthfill dam with stone slope protection. The dam is 1,150 feet long with a maximum height of 75 feet; there are two earthfill dikes with stone slope protection totaling 1,650 feet. Little Hill Dike, located about three miles northwest of the dam, is 1,230 feet long and has a maximum height of 28 feet; and Dodge Dike, situated about .5 mile west of the dam, is 420 feet long with a maximum height of 20 feet. There are three gated rectangular conduits. Each conduit measures five feet three inches high, three feet six inches wide, and 65 feet long. A fourth ungated rectangular conduit was permanently plugged in 1951 to increase the effectiveness of the reservoir during flood periods. A spillway is cut in rock with a 240-foot-long concrete weir.

While the main purpose of Blackwater Dam is to provide flood risk management to the Merrimack River Basin, over the years the project has become known for its recreational opportunities such as fishing, hunting, horseback riding, snowmobiling, etc. The U.S. Army Corps of Engineers manages the natural resources at Blackwater Dam for multiple uses: flood risk management, wildlife habitat, forestry, watershed protection, and outdoor recreation. All project lands and waters are under the jurisdiction of CFR Title 36 regulations, state, and local laws.

The U.S. Army Corps of Engineers is updating the Blackwater Dam Master Plan. The Master Plan is the strategic land use management document that guides the comprehensive management and development of all project resources throughout the life of a USACE project. The Master Plan guides efficient and cost-effective management, development, and use of project lands. It is a vital tool for the responsible stewardship and sustainability of project resources for the benefit of present and future generations. The Master Plan guides and articulates USACE responsibilities, pursuant to federal laws to preserve, conserve, restore, maintain, manage, and develop project lands and waters and associated resources. The intent of an updated Master Plan is to present a current inventory and assessment of resources, provide an analysis of resource use, and evaluate existing and future needs required to protect and improve the value of resources at a project.

The current Blackwater Dam Master Plan, last approved in 1997 (and prior version in 1967), needs revision to address changes in regional land use, population, outdoor recreation trends, and the USACE management policy. Previously, this page included the 1967 Master Plan as the last approved version, but has been updated with the 1997 Master Plan as the latest version. Key topics to be discussed in the revised Master Plan include revised land use classifications, new natural and recreational resource management objectives, recreation facility needs, and special issues such as invasive species management and threatened and endangered species habitat. The Master Plan revision WILL NOT address the technical and operational aspects of the dam related to flood risk management or the water conservation missions of the project. During the process, the team will collect data, conduct analysis, prepare a draft report (which will become available for public and agency comments), and ultimately finalize and adopt the new Master Plan.

The U.S. Army Corps of Engineers (USACE) will host an open house on Thursday, April 10, 2025, from 4:00 - 6:00 p.m. at the Webster Town Hall, to share details on a draft revision process of the Blackwater Master Plan and showcase the existing land use classification maps, which are original from 1967.  A 30-day public comment period began on April 10, 2025, and will end on May 8, 2025.