Water quality is a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose. Although scientific measurements are used to define water’s quality, it’s not as simple as saying “this water is good” or “this water is bad.” After all, water that is perfectly good to wash a car with may not be good enough to serve as drinking water at a dinner party for the President (USGS, 2006). The quality of water can be degraded by pollution that enters the stream from both human activities and natural causes.
What water quality tests reveal can be thought of as the watershed's "report card." How well we live on the land is reflected in the health of our streams.
Polluted runoff is the most common cause of water pollution in Montana. As more land becomes compacted and hardened due to human activity, less rainfall and snowmelt are absorbed into aquifers, and more water runs offs the surface. As it travels over the landscape, the water can collect polluntants. This pollution is also referred to as Stormwater Runoff. See the stormwater links for more information on how you can prevent pollution from reaching your local streams.