Causes of an Unhealthy Lake


Do you know what causes a lake to become unhealthy? Do you know the difference between point and nonpoint source pollution? Find out here!


Nonpoint source pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away pollutants, finally depositing them into the lake. Nonpoint source pollution can't be tracked down to one specific location, as it comes from multiple places. 


Unlike NPS pollution, a point source pollution comes from a single, indetifiable location. Often, it will deposit into the lake from a pipe that connects to a factory or water treatment plant. 


Fertilizers cause rapid growth of algae. Dying algae feed bacteria, which consume so much dissolved oxygen that fish and plants cannot survive. Some species of algae also produce toxins that can be harmful to humans.

Animal Waste

Poop from dogs, cows, cats and numerous other animals can pollute the lake. As the rain washes the feces into the lake, the water becomes filled with gross waste that isn't good for the health of a body of water. 

Water Treatment Plant

Our sewer and septic systems are responsible for treating large quantities of waste. These systems do not always operate properly or remove enough nitrogen and phosphorus before discharging into waterways.


Factories often dump untreated waste into the water. They often have a pipe leading from their factory to a body of water. Many pollutants from factories are toxic to the marine life and a hazard to our health.

Road Salt

Road salt can cover and destroy plants that water creatures depend on for food and shelter. If there's too much road salt in the lake, the water becomes salty and the chloride becomes toxic to fish.

Car Washing

The soaps and chemicals you use to clean your vehicle can go right down your driveway and end up in the lake. Many are toxic to fish and unhealthy to swim in or drink from. 


Once the leaves get into the water, they release nutrients that contribute to the accelerated growth of algae. The algae can kill aquatic critters and make swimming and drinking from the lake unpleasant.


Trash is a big source of water pollution. The litter that you carelessly throw on the ground is washed into the lake. It can be a big threat to the wildlife, especially birds, who eat and get tangled up in the waste.