What is Water Quality?

The term water quality is generally used to describe the chemical, physical and biological characteristics of water with respect to its suitability for its many particular uses. For example, water quality as it relates to drinking has different requirements than water suitable for fish and other aquatic life, not to say that water safe for drinking will not support other uses. The point here is that there is a lot to consider when determining water quality. Even when looking at the data from scientific field monitoring, it is not as simple as saying “this water is good” and “this water is bad.”

Below are some of the health standards for both humans and aquatic life for some of the elements and parameters found in our state’s waters. You can see that the difference in the standard varies depending on the parameter or element.


Human Health Drinking Water Standard

Aquatic Life Standard

Turbidity 1.0 NTU (turbidity unit)
Mercury 0.05 μg/L (parts per billion) 0.91 μg/L (parts per billion)
Dissolved oxygen N/A (we don’t breathe through gills!) 6.0 mg/L (minimum, 7-day avg.)
Copper 1,300 mg/L (parts per million) 2.85 mg/L (parts per million)
Arsenic 10 μg/L (parts per billion) 150 μg/L (parts per billion)

More information about Montana’s water quality standards and national water quality standards can be found at the Montana Department of Environmental Quality (DEQ) Water Quality Information website.

Human contamination of stream flows, groundwater and surface runoff (e.g. storm water) will have consequences for water quality. In this module field study we will try generally determine what the quality of our water is using scientific method. Next, we will explore the four basic chemical and physical parameters you will use via the World Water Monitoring Day test kits to determine something of your site’s general water quality.


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The MSP project is funded by an ESEA, Title II Part B Mathematics and Science Partnership Grant through the Montana Office of Public Instruction. MSP was developed by the Clark Fork Watershed Education Program and faculty from Montana Tech of The University of Montana and Montana State University, with support from other Montana University System Faculty.