Riparian plantings along the Walla Walla River should help filter polluted runoff and shade the river. Picture courtesy of the Environmental Assessment Program, WA Department of Ecology.

The Environmental Importance of the Different Impairments


Elevated water temperature is a common problem in many Washington State streams. When temperatures are too high it can make the streams uninhabitable for fish and other aquatic animals. Many salmon and trout species suffer a variety of ill effects, from decreased spawning success to death, when waters are too warm. The optimal temperature for most salmon and trout species is between 12-14˚C (54-57˚F).  Temperatures in the 23-25˚C (73-77˚ F) range can be lethal, depending on the species. The water temperature can also affect how much oxygen is dissolved in the water. Fish need this dissolved oxygen (DO) to breathe. The warmer the water, the less DO it can hold. Warmer water temperatures also tend to speed up the metabolism of the fish so they require more oxygen for biological functions.

To learn more about temperature and DO check out our focus sheets:

Effects of Elevated Water Temperatures on Salmonids

Dissolved Oxygen and the Water Quality Standards


Fecal coliform bacteria

Fecal coliform is a group of bacteria found in the feces of warm-blooded animals. When found in bodies of water, it can indicate the presence of other disease-carrying organisms. Fecal coliform bacteria can get into water bodies from failing septic systems and animal waste. High levels of fecal coliform in the water can affect public health, economy, and environmental quality in a community.

A long history of illness outbreaks and epidemics points to a relationship between the presence of fecal coliform bacteria and the presence of illness-causing viruses and bacteria, called pathogens. These pathogens can be accidentally swallowed. People swimming or playing in water can be exposed to pathogens when they enter the body through small cuts, abrasions or mucus membranes.

Some of the symptoms of illness associated with fecal coliform pathogens are minor, such as upset stomach, diarrhea, ear infections, and rashes. However, some pathogens, such as E coli, hepatitis, and Salmonella, can have very severe health effects. Washington’s water quality standard for fecal coliform bacteria is set to protect public health.

For more information on fecal coliform check out our Fecal Coliform Bacteria and Washington’s Water Quality Standards focus sheet.



pH is a measure of how acidic or basic the water is (in other words, a measure of the concentration of hydrogen ions). A higher pH means there are less free hydrogen ions available than at a lower pH. The pH scale (0-14) is logarithmic; that is, one unit of change in pH equals a tenfold change in the number of hydrogen ions. For example, there are 10 times as many hydrogen ions available at a pH of 7 (pH neutral) than at a pH of 8. This affects the chemistry and chemical reactions that take place in the water. The pH of the water is also important to the fish and animals that live in it. The pH of streams should be between 6.5 and 9.0 to protect freshwater aquatic life.

The pH can affect the solubility of nutrients and metal compounds. By affecting the solubility of nutrients, it can change the amount of nutrients available for plant growth. If too many nutrients are available, aquatic plants can grow out of control. When these plants decompose, they can deplete the water of oxygen. The solubility of many metal compounds also changes greatly with pH. Generally, reducing the pH (more acidic) increases the solubility of heavy metals. When more metals dissolve in the water, aquatic animals may absorb them faster. Therefore, a lower pH (more acidic) may increase the toxicity of these metals to aquatic life.

pH Scale Graphic.  Graphic source:  The Stream Scene. Chart showing various pH levels and effects (click on chart to see full view)


PCBs and Pesticides

Pesticides and PCBs can be toxic to fish and wildlife that use a contaminated water body.

PCBs are polychlorinated biphenyls. In the past, PCBs were used as coolants and lubricants in electrical equipment, such as transformers and capacitors. The United States banned the manufacture of PCBs in 1977 because they build up in the environment and can be harmful to humans and wildlife. PCB exposure can occur if you:

The pesticides found in the Walla Walla River are no longer in use but still create ecological problems:

Although the United States banned these pesticides over a decade ago, they tend to persist in the environment. They can be toxic to fish, wildlife, and humans when they eat contaminated foods.

To learn more about PCBs, see the Agency for Toxic Substances and Disease Registry’s (ATSDR) fact sheet.

To learn more about PBTs and pesticides, see the Agency for Toxic Substances and Disease Registry’s (ATSDR) fact sheets:

DDT and its derivatives



Heptachlor and Heptachlor Epoxide


If you have pesticides you no longer use check the following Web site for free pesticide collection events:

Washington State Department of Agriculture Pesticide Management - Waste Pesticide Collections

Contact Us for more information


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Last updated June 2011