Non Point Source Pollutants in the Watershed

What are non-point source pollutants (NPSP) that affect Alberta’s rivers, streams and lakes?

The Alberta Water Council (AWC) has reported on those sources of contaminants in a series of consultant studies issued in recent years. Here’s what they are:

Non-point source pollution (NPSP) is contamination that enters a water body from many dispersed points of discharge and thus has no single place of origin. This is different from point source pollution, which comes from one source and is generally easier to measure and manage because the emissions are licensed and controlled.
The United States Environmental Protection Agency explains NPSPs in this way:
Nonpoint source pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. Non-point source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters and ground waters.
In an agricultural watershed like ours, surface water that flows off the land can carry dissolved and suspended materials  into Sylvan Lake and affect the quality of lake water. A previous post on this site explains how that can occur. The low level sources are everywhere: the pore water in the soil; decaying organics; lawn care fertilizers and chemicals.
For more background, consult these AWC publications:


How do we know that happens? Here’s a short report on a turfgrass experiment in Wisconsin that measured fertilizer runoff from lawns. Spring runoff over frozen ground carried away more nutrients than summer runoff during the growing season.

4R nutruent stewardship is a key part of watershed best practices. Know your NPK nutrients because they can become a NPSP that impacts the lake. Algae like nutrients too.

Urban lawns are an easy target for NPSP regulators. There are plenty of municipal bylaws that restrict fertilizer applications. But there’s more to the story of properly applied plant nutrients than just control of runoff into water bodies.  Fertilizer Canada advises that healthy lawns are important to communities too: A 50 x 50 foot lawn can produce enough oxygen for a family of four each day!




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