Water Resources Cascade Conservation District - Cascade County Conservation District - Great Falls, Montana

What is Stormwater?

When it rains or snows, water falls everywhere.  Some falls on the ground where it soaks in, and some falls on impervious surfaces which cannot absorb moisture.  Roofs, roads and parking lots are some obvious examples of impervious surfaces.  When water falls on them, it mixes with whatever other materials are there on those surfaces.  For roads and parking lots, that can include automotive chemicals like petroleum, antifreeze and other liquids, as well as solids from tires and brake materials.  It includes the components of asphalt, and any garbage or spills that humans have left behind.

At home, yard fertilizers and pesticides can spill onto driveways and sidewalks.  And lets not forget our animal friends, who leave behind waste too!  Construction areas expose large areas of soil to erosion.  All of these substances can get washed away in rain and snow.  Where do they go?  Into the stormwater system.

The stormwater system includes all the gutters, curbs and drains that carry water away from impervious surfaces and into our streams.  Much of it receives no treatment at all, so whatever is washed away goes right into our streams.

As the land area becomes more developed for human activity, the amount of impervious surface increases.  There is less surface area available to absorb water, so the amount of precipitation that ends up as stormwater increases.  That is coupled with an increase in the amount of unhealthy or toxic substances in the water that are being discharged to our surface waters.

Stormwater and Watersheds

The Flathead Lake watershed includes most of Flathead County and then some. Starting in Canada at the smallest tributaries (headwaters) of the North Fork, the Flathead Lake watershed includes all land that drains into the Stillwater, Whitefish, and Swan rivers; the North, Middle and South Forks of the Flathead, and Ashley Creek. The City of Whitefish and many individual landowners derive their drinking water from these surface waters.

Where does the water falling on your roof go when it leaves your gutter? What about all that water in store parking lots? Find out about watersheds and storm water. Learn what you can do to keep our drinking water clean and healthy with these Water Quality Tips for Homeowners.

Stormwater Control:  Implementing Construction Site BMP’s

BMP’s are Best Management Practices.  The purpose of this project is to assist contractors in the installation, evaluation and enhancement of stormwater BMPs in the Northern Rocky Mountains. A graphic guide and resource library can be found at http://stormwater.montana.edu/

Riparian Areas – Nature’s Water Filters

Riparian areas are the land areas adjacent to bodies of water.  They contain water-loving plants and robust specimens of upland vegetation.  While the specific vegetation type is variable, they are characterized by presence of trees and shrubs in along most undisturbed Cascade County streams.  As a thank-you for all that water, the vegetation works to help keep the water clean.  The live, dead and dying plant and animal materials in a healthy riparian area  form a thick layer of of organic materials called duff.  What looks like a messy pile of dead leaves is really very important for water quality.  The deeper you go in the duff, the more decomposed it is.  Duff has an amazing water holding capacity.  When water falls on it, it infiltrates slowly, allowing time for the pollutants contained in the water to be filtered out and/or broken down.  When water flows over it, the roughness provides friction to slow the water down.

Flood waters can soak into the spongy riparian area and remain stored there to release to the stream much later.  All the shade keeps the area cool and moist.  If you are lucky enough to own waterfront property, we encourage you to establish, enhance and maintain your riparian area.  To learn more about riparian areas, visit the Watersmart Montana website.