Negative Consequence of Retention Ponds

Excessive Algae Growth

• Excessive algae growth causes problems including fish deaths, unpleasant odors, and a green, slimy appearance to the water. These problems can lower the value of adjacent properties. Excessive algae growth is caused by an overabundance of nitrogen and phosphorus, which in turn is caused by fertilizer runoff from lawns and agricultural properties. To control excessive algal growth, fertilizer use should be limited within the retention pond's drainage basin.

Poor Water Quality

• Retention ponds can have high levels of bacteria, harmful zoo plankton, and pesticides in addition to excessive algae growth. These can cause illness if the retention pond is used for swimming or boating, or if fish are consumed from the retention pond. In the interest of public safety, retention ponds should be closed to swimming and the harvest of fish.

Sedimentation

• Retention ponds fill with sediments over time. The type of sediments depend on the location of the retention pond. Retention ponds in urban areas and adjacent to heavily traveled roadways may contain heavy metals and other contaminants in their sediments, which can pose a public health risk if disposed of improperly. Those sediments must be removed if the retention pond is to fulfill its original purpose, to retain water. Such sediments should be disposed of on non-agricultural land.

Mosquitoes

• Retention ponds can serve as breeding grounds for noxious insects, especially mosquitoes. Controlling aquatic vegetation helps to control mosquitoes. Maintaining a water depth of six or more feet helps to limit rooted aquatic vegetation by limiting light at the bottom of the pond, and herbicides can be used to control algae and other vegetation that grows in shallow water and at the surface of retention ponds. Mosquitoes can also be controlled by the introduction of certain species of fish, such as gambusia or misquito fish, which feeds on mosquito larvae.

Waste and Trash

• As retention ponds are filled in by runoff from the surrounding area, the runoff can often contain yard waste and street trash. This trash can turn the retention pond into an eyesore and damage adjacent property values. Retention ponds should be regularly policed and cleared of trash.