Your Water Quality and Macroinvertebrates
Ted Lange
The South Grand River Watershed
A watershed is only as good as the water that flows through it, and everything in the watershed affects the quality of that water. The species, numbers, and diversity of plants agricultural land, impervious cover of highways, parking lots, buildings, industrial discharges into streams etc., all have an effect —good or bad—on the quality of water in streams. We can learn much about the quality of water in a stream from the macroinvertebrates (tiny aquatic animals without a vertebrae) living in the water because they are indicators of water quality. Volunteer groups often do the work of gathering the information these aquatic animals can provide. This article is a brief broad overview of how water quality is diminished; how aquatic animals tell us the status of water quality; and who participates in the work to collect the data.
Every watershed has a beginning and an end. The Missouri Department of Conservation (MDC) has divided Missouri into 20 watershed Units. Within each unit are multiple watersheds—all flowing to a common destination. The South Grand River Watershed is in the north portion of Unit 11 and flows from near Belton in Cass County to its end in Truman Lake. The South Grand River Watershed Alliance (SGRWA) is one of 22 Associations, the only one in Unit 11, with some of the 20 Missouri Units having multiple Associations and about five having no Associations.
According to MDC, many streams in the South Grand River Watershed (SGRW) suffer from water quality problems. A contributing factor could be that the South Grand River (SGR) is mostly supplied by runoff from rain. There are very few other sources such as springs or ice melts contributing water to the South Grand River.
There are 13 cities with a population of 1,000 or more in the SGRW. These cities are a consistent year-round source of water to the SGR since they discharge their treated waste water into streams of the watershed that feed the SGR as well as into the South Grand River itself. This may sound gross, but it is a source that contributes to keeping the water moving and the treated waters are tested and controlled so that water is actually clean. In addition to the treated water discharged from sewer plants into streams, runoff from hard surfaces (streets, parking lots, rooftops, etc. is channeled directly into smaller streams feeding the SGR and into the SGR. This runoff enters streams via storm sewers that pipe the runoff, untreated, directly to streams.
Earlier in Cass County’s history, the activities associated with coal mining were a significant source of contamination in several streams of the SGRW. While these sites have mostly been cleaned up, several streams in the SGRW are on the impaired list due to the continuing impacts of those coal mining activities. While other SGRW streams are impacted by activities such as stream channelization and runoff containing sediment and contaminants from agricultural activities, the sources most of us are in contact with are the contaminants such as road salts, oil, lawn fertilizers, pesticides, etc. that are washed, with no treatment, down the storm drain directly to the waters of the watershed.
Of course, as the old saying goes, ‘the best solution for pollution is dilution’ still fits—but that doesn’t mean it isn’t there. This area receives an average of about 40″ of precipitation per year, and rains do flush out the river quite often during the year. These diluted pollutants are reduced to tolerable levels and flow on downstream for further dilution.
What aquatic animals (macroinvertebrates) tell us about water quality
Aquatic macroinvertebrates are animals without a backbone that live in the water. Many are the larval stage of some insects such as dragonflies, mayflies, stone flies, etc that spend that stage in a small area of a stream or snails, crayfish, worms and others that move only short distances from where they live—sand, gravel, rocks are the first things that come to mind in a stream, but leaves, twigs, and muck are more commonly found in the SGR. Spending their entire lives in a very small area makes them sensitive to pollutants in the stream water. Some are intolerant of any pollutants, while some species are able to tolerate some pollution and others can tolerate very polluted waters. This fact makes them highly valued in assessing the degree of pollution within the stream area they live. For example, finding only macroinvertebrates tolerant of polluted water such as black fly larvae, leaches, and others but no pollution intolerant species such as caddisfly or mayfly larvae reveals a lot about the level of pollution in that particular area of a stream.
To collect macroinvertebrates the first step is to dislodge some from their microhabitat with the most common process being to locate a riffle (shallow moving water) and set up a collection net downstream. Next kick or shallowly dig (3- 6 inches) into the stream bed to move the macroinvertebrates from their microhabitats. After they are collected in the net, they can be taken to shore, separated according to species, identified and counted. Macroinvertebrates are very small but easily identified with an identification chart featuring a key under each photo or drawing. *see resource
The counting and compiling of the numbers give an EPT* index of pollution tolerance. While the EDT index number is an indication of water quality, it does not provide the reason for that level of water quality. Physical and chemical testing are required to obtain enough information to determine what is actually in the water.
Why does all this matter? By learning about the health of our watershed and components of a healthy watershed with quality water in its streams we can each become aware of our own actions and make decisions in our own lives and for our community to improve the health of our watershed and of our lives.
*EPT: Pollution intolerant species (Ephemeroptera (mayflies), Plecopters (stoneflies), and Trichoptera (caddisflies)
Note: See opportunities to participate in two stream cleanup events (October 26 and November 2) each includes a stream monitoring demonstration.
For information on becoming a member of Missouri Stream Team and learning how to monitor streams:https://mostreamteam.org
Resource: Missouri Stream Team Guide to Aquatic Macroinvertebrates (includes information on materials needed and how to do a stream sample:https://mostreamteam.org/assets/missouristreamteamguidetoaquaticmacroinverts.pdf