Souhegan Watershed Association
Souhegan Water Quality
Water in the Souhegan River is classified as class "B" water for its entire length. Class "B" water is fishable or swimable, so Souhegan water is generally of good quality.
There are two general types of pollution: point source and non-point source pollution. Point source pollution comes from a specific identifiable point such as a pipe. Nonpoint source comes from a collection of sources such as runoff from roads, fields, lawns, parking lots, construction sites, and erosion.
The primary threat to the Souhegan today is from nonpoint source pollution. Nonpoint source pollution is very hard to pinpoint and correct. Our water quality testing program has identified excess nutrients, bacteria, heavy metals, and sediments that have washed into the river. Some of this is natural and unavoidable; some is manmade and correctable.
The major sources of nonpoint pollution are:
Fertilizers, pesticides, and herbicides - When excess chemicals or manures are applied to a lawn or field, the grass cannot take up the nutrients fast enough. The next rainstorm washes the excess into the nearest storm drain or stream and eventually into the river. This causes excess plant growth in the river. This excess plant growth uses up large amounts of oxygen in the water. This lack of oxygen chokes the fish, insects, and habitat and diminishes their population. Excess phosphorus, which is found in the Souhegan, can be identified by green, moss-covered rocks under the surface. The waste treatment plants on the Souhegan in Greenville and Milford cannot yet remove phosphorus from the wastewater, so any soaps containing phosphorus flushed down your home drain go directly to the river.
Septic systems - Failing or inadequate septic systems, especially those near a waterbody, can cause bacteria, viruses, and nutrients to migrate into the ground water or river. This can be harmful to humans and causes sickness to swimmers.
Stormwater runoff - Precipitation that falls on roads and parking lots flows to storm drains that flow directly to the river, some from great distances. This carries gas, oil, salt, fertilizers, chemicals, sand, waste Ė whatever goes into the drain.
Erosion - Soils that wash into the river increase turbidity, destoy habitat and abrade the delicate gills of fish that live there.
What You Can Do To Help
Web pages by Richard Hart.