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.
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.
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