How do you determine water quality?
Every year, the Iowa Department of Natural Resources (DNR) conducts routine sampling of Iowa’s water resources as part of the state’s Ambient Water Monitoring Program. The purpose of ambient monitoring is to gather baseline, or background information so that stream health can be tracked over the course of time. The Ambient Water Monitoring Program collects data on temperature, dissolved oxygen, pH, and other physical conditions of the stream. Samples of the water are taken and sent to the lab for analysis of chemical conditions, such as nitrate levels, scans for pesticides and herbicides, and other contaminants.
With physical and chemical monitoring, a "snapshot" in time is taken of the water's condition. A single sample does not provide very useful data, as a recent rainstorm, drought, fertilizer application, or any number of conditions may have influenced the condition of the water at the time the sample was collected. Many samples over a period of time are needed to get an accurate picture of the water quality of that waterbody.
The Iowa DNR also conducts biological monitoring
on streams throughout the state. During these biological assessments, data is collected on not only the chemical and physical conditions of the stream, but also the biological component as well. Benthic macroinvertebrates (aquatic insects that live on the stream bottom) and fish are collected and indentified. Since these creatures live in the water at all times and typically don't move from the area very far (especially the benthic macroinvertebrates), they give a reliable indication of the general water quality conditions of the stream over time. The types of species found (or not found, in the case of polluted or poor-quality waterbodies) can then be used to determine the quality of the stream. For example, certain types of organisms (like caddisflies, stoneflies and mayflies) can only survive in clean, pristine conditions. A disappearance of these species may indicate a problem with water quality. Changes in the biological health of a water are more gradual and less influenced by localized events such as rainstorms, providing information that may not be present in chemical or physical water sampling.
Data from fish tissue monitoring is used to determine if a waterbody designated for fish consumption meets meets those uses. Should results indicate a problem, fish consumption advisors may be issued for the body of water.
Fish kills may also indicate a problem with water quality. Several factors can lead to a fish kill – both naturally occurring and otherwise. Fish cannot live if there isn’t enough oxygen in the water, so physical testing may be used to describe the physical attributes of a waterbody including such things as dissolved oxygen, pH, temperature, transparency, and suspended solids. If a sufficient supply of dissolved oxygen is not present, then chemical testing may be used to describe the chemistry within the water. Chemical analysis includes checking levels of phosphorus, nitrogen, and chemicals. Excessive nutrients can lead to overabundant algae, which in turn consumes oxygen as it dies, thus depriving the fish of necessary oxygen.
What do you do with the information?
Information from all these types of monitoring (ambient, biological, fish tissue, and fish kills) is used for purposes of assessing the level of water quality in Iowa's streams, rivers, and lakes. These assessments for the basis for the state's 305(b) report and 303(d) list of impaired waters.