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A watershed is the area of land that drains to a stream, river, pond, lake, or reservoir. It can be divided into smaller subwatersheds to compare characteristics such as drainage area, land uses, stormwater runoff volumes, stream flows, and water quality to determine which areas have the greatest threats to water quality and quantity. This layer provides a simplified graphic depiction of the 10 subwatersheds of the Pennichuck Watershed.
Monitoring Sites Layer
Nine tributary locations have been continuously monitored for flow and total phosphorus since 2007. Flow monitoring is performed to obtain an overall understanding of how streams, rivers, and ponds respond to precipitation throughout the watershed. Total phosphorus monitoring is performed because it is a key pollutant that can lead to excess algal growth. Total phosphorus monitoring is also performed at five in-pond locations to evaluate the water supply`s response to the phosphorus loads from the watershed. Groundwater monitoring for total phosphorus at the nine tributary sampling locations or nearby began in 2013 to help determine phosphorus loads coming from groundwater baseflow versus from stormwater runoff. These monitoring sites are shown on this layer with graphs of tributary phosphorus, groundwater phosphorus, and/or flow data.
Best Management Practices Layer
Parts of the Pennichuck Watershed contain some of the most developed land in the state, much of which was developed between 1960 and 1990, before best management practices (BMPs) to treat water quality were required or used. To address the challenge of existing pollution, Pennichuck has been involved in the design, construction, and continued maintenance of several stormwater BMPs within the watershed. This layer identifies the location of these BMPs and also provides a photo and description of each.
Land Use Layer
Land use impacts water quality and quantity because developed areas with more impervious cover contribute more pollution, including heat pollution and high velocities, than less developed areas, especially where BMPs are not used to treat stormwater runoff before it is discharged. Runoff from future development can be controlled to minimize the pollutant loads from new impervious surfaces. This layer provides a map of Forest, Open Space, Residential, Commercial, and Industrial Land Uses.
Land uses within the watershed influence water quality and quantity because developed areas with more impervious cover contribute more pollution, including heat pollution and high velocities, than less developed areas. Pennichuck’s most recent tool to address pollutant loads from the watershed is the Watershed Restoration Plan. This plan uses a Total Maximum Daily Load (TMDL) approach to identify sources and quantities of pollutant loads, acceptable pollutant loads, and methods to reduce them.
Pennichuck has carried out various other initiatives to improve the health of the watershed including technical studies, construction projects, and community outreach programs (see the BMP information on the Watershed Interactive Map).
Partial funding for some of these projects was provided in part by a Watershed Assistance Grant from the NH Department of Environmental Services with Clean Water Act Section 319 funds from the U.S. Environmental Protection Agency.