Polluted Runoff Water

Polluted Runoff Water

Polluted Runoff Water

As New Hampshire’s forested land is cleared for homes, businesses, roadways, and parking lots, the natural ability of the landscape to soak up melted snow and rain water decreases. Because of this, more runoff water travels across pavement and lawns, picking up pollutants on the way into our lakes.

The water quality of a lake is primarily determined by what flows into it from the surrounding landscape (the watershed).

Typical pollutants in runoff water include fertilizer, road salt, waste from septic systems and animals, and soil. Once in the lake, these pollutants degrade its health in many ways.

Over ninety percent of the water quality problems in New Hampshire’s lakes and rivers are caused by polluted runoff.

Watershed Pollution Types

Other Threats to Water Quality


New Hampshire’s lakes have seen a record number of toxic cyanobacteria blooms for the past three summers. These blooms can produce toxins that make people, pets, and wildlife sick.

Climate Change

New Hampshire is experiencing increased precipitation, but it’s happening in fewer storms. This means that larger rainstorms occur after dry periods. As a result, the land can’t soak up all the rain at once, leading to more runoff water and nutrients entering our lakes that contribute to the growth of native and invasive plants, algae, and toxic cyanobacteria.

monitor manage invasive species nh lakes

Invasive Species

Our lakes are home to many different kinds of plants and animals that are good for the lake. But, some species are harmful to our lakes.