Water Quality

Water Quality

Water Quality in New Hampshire's Lakes

New Hampshire is home to approximately 1,000 lakes and ponds—some of the cleanest and healthiest lakes in the country. However, in many of our lakes, there has been a downward trend in water quality over recent years.

What drains from the land into the water is the main factor affecting the water quality in rivers and lakes.

The NHDES publishes a eport every two years that details the condition of New Hampshire’s lakes and ponds, analyzes how well they support the growth and survival of a healthy population of shellfish, fish, and animals, and support recreational activities in and on the water. Some waterways are classified today as being impaired, meaning they are not healthy enough to support a variety of organisms and uses.


To learn more about the NHDES analysis please visit: https://www.des.nh.gov/water/rivers-and-lakes/water-quality-assessment

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

Invasive species are organisms that thrive in an area where they did not naturally develop and that cause harm to the economy, environment, or people. Learn more about the species we are most concerned about and what you can do to prevent them!

nh lakes flooding

nh lakes runoff

Polluted Runoff Water

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