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Water Quality


Pesticides

 

Fertilizers: The River a Little Too Well Nourished

People in a canoe on the Rideau River.

Nitrogen and phosphorus are natural fertilizers, and so are normal parts of a healthy river.

Nevertheless, too much fertilizer causes explosive growth of plants and algae. While algae are an important food for many invertebrates, fish and ducks, too many algae can clog the waterway. Also, masses of decomposing algae reduce the amount of oxygen in the water that is available to the animals of the river.

Phosphorus is used in fertilizers for agriculture, lawns and gardens, as well as in detergents (in the form of polyphosphate). Phosphorus finds its way into the River in runoff.

Massed algae.
Massed algae.
Excessive Phosphorus in Summer
The amount of phosphorus in the Rideau River is elevated, but falls in the middle of the acceptable range noted in the Canadian Water Quality Guidelines for Freshwater Aquatic Life (CWQG). [11]

More precisely, phosphorus levels exceeded the guidelines during the summer months in the stretch of the River that lies within the City of Ottawa. The River is "a little too well nourished", according to Paul Hamilton, a researcher who specializes in the study of algae at the Canadian Museum of Nature.

Two causes have contributed to the situation there. In one, agricultural fertilizers and urban discharge are naturally carried downstream by the River's current. In the other, the large number of paved roads, parking lots and buildings found in urban areas reduces the surface area that will permit water to be absorbed into the ground, and as a result, runoff is not adequately filtered before it reaches the River.

Green frog, Lithobates clamitans.
Green frog, Lithobates clamitans.

In some towns, storm sewers have the shape of a fish built into its design, in order to signify to citizens that the sewers lead directly to the River and so their contents is not treated.


Nitrogen
No guidelines have been set by the CWQG for nitrogen levels because healthy levels vary in proportion to the amount of phosphorus that is present. Analysis of nitrogen levels found in the Rideau River has begun, undertaken by a student from the University of Ottawa.

 

Arrow.  
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Bullet. 
Bullet. 
Arrow.  
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Arrow.  
A Project of the Canadian Museum of Nature
  
 Images: Thomas Cook, Jean Lauriault