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).
Common pollutants in runoff water include fertilizer, road salt, animal waste, and soil. Once in the lake, these pollutants degrade the health of the lake in many ways.
Over ninety percent of the water quality problems in New Hampshire’s lakes and rivers are caused by polluted runoff water.
Watershed Pollution Types
While all lakes need some amount of nutrients to support plant and algal growth, too many nutrients—particularly phosphorus and, to a lesser extent, nitrogen—degrade the health of our lakes. Too many nutrients in our lakes can cause an increase in the growth of invasive and native plants, bacteria, algae, and toxic cyanobacteria blooms.
Nutrient pollution is primarily carried into our lakes in runoff water that flows across the landscape and into our lakes, picking up fertilizer, animal waste, and eroded soil, which can all be high in nutrients. Nutrient pollution can also seep into the lake through surface water and groundwater contaminated by effluent from inadequate and failing septic systems.
Nutrients can also be mixed into the lake when shorelines and lake bottoms are disturbed naturally by winds and wave action and also by wakes produced by boating activities.
Many of New Hampshire’s lakes are being harmed due to phosphorus pollution.
Dramatic and rising concentrations of chlorides from salt applications have been identified in New Hampshire’s waters due primarily to the use of salt (sodium chloride) on roadways, walkways, and parking lots during winter.
Chloride can be toxic to aquatic life and can foul waters used for drinking water supply.
This problem is increasing in severity. In 2008, 19 waterbodies were listed as being impaired due to chloride pollution. In 2020, 50 waterbodies were listed as being harmed due to chloride pollution.
Other Threats to Water Quality
Cyanobacteria
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!
by NHMB