Stream watch

science and technical writing

Stream Watch How identifying and counting the organisms in a stream determines the quality of the water. Anyone with a little knowledge can do it.

By Rob Crimmins

A stream’s health can be determined through chemical analysis but testing for individual chemicals can be expensive so volunteers in the Delaware Stream Watch Program let the wildlife, primarily insect larvae, tell the story. Chris Brown with the Delaware Nature Society shows landowners and others interested in streams in the Delaware and Chesapeake Bay watersheds how to determine a stream’s condition.

Recently Chris held a workshop on the Johnson Branch of the Murderkill River in central Delaware. Most of the participants were educators in a Wilmington (Delaware) College teacher certification program and the others were landowners who wanted to know more about the waterways on or near their property.

The Nature Society’s Headquarters is in the Ashland Nature Center in Hockessin, Delaware on the Red Clay Creek. The ground there is different from the land around Johnson Branch so the first aspect of stream survey that he explained was the effect of geography. Hockessin is in the piedmont of the Appalachians. Bedrock is at

the surface in places and elevation can vary quite a bit along a stream’s length. The Red Clay, in northern Delaware, flows more swiftly than almost any stream in the southern counties of Sussex or Kent where the bedrock is under thousands of feet of sand and the slopes are gentle. A rapidly flowing stream will not support the same wildlife in the same way as one that flows as slowly as the Johnson Branch. The other major geographic influence is whether or not the stream is in a tidal area. Salinity and the water’s daily rise and fall are the issues in streams that are affected by tides.

These factors are among those that establish what can live in any given stream but they don’t change the basic method of determining whether or not a stream is healthy.

That’s done mostly by identifying and counting the organisms that live there. If a stream is well populated by a wide variety of plants, animals and insects than it is a healthy stream.

If there are very few insect larvae or if few species are represented the stream is probably sick. The Stream Watch Program enlists

the help of volunteers to monitor streams to identify the ones that need help and protect the ones that don’t.

If you adopt a stream or “tax ditch” you’re asked to complete a survey either once a month or quarterly.

The survey calls for qualitative and quantitative observations of a 100-yard length of stream and completion of a data sheet, which you send to Delaware’s environmental protection agency, DNREC. Over fifty categories of information are recorded and they include the name of the surveyor and the name of the stream, it’s watershed and location, velocity, width, depth and bottom type, the water color and odor, the surface coating if any and the streambed coating. The data sheet also asks about algae, vegetation, fish, reptiles, birds, mammals, amphibians, trees, shrubs and small plants.

When pressed, Chris admitted that the survey appears far more scientific than it is. The main purpose is to establish a starting point for investigation by professionals if a stream shows signs of damage and as a means of educating the volunteers so that they will appreciate and assist in protecting their neighborhood streams.

The back page of the data sheet asks for information that requires some detective work. The “macroinvertebrate survey” is the fun part for those who are fascinated by a living world that is normally unseen and according to Chris it’s the most important aspect of the survey. If you were (or are) a kid who kept (or keeps) bugs in jars you might want to consider adopting a stream. Macroinvertibrates on the Tidal Survey Data Sheet include crabs, shrimp, shellfish, worms and some insects but on the Non-tidal Data Sheet they are mostly insect larvae. To survey the bugs you take a net, swish it though a place where you think there might be something, dump the contents into a large, white dishpan and pick out the critters. If you find larval stoneflies and mayflies chances are the stream is in good shape. As indicators of stream condition stoneflies are “four star” bugs. They need clean water with high levels of dissolved oxygen and neutral pH. Mayflies are “three star” bugs so they need pretty good water too but they’ll survive in conditions that would kill a stonefly.

Caddisflies have a two star rating while true flies like midge flies, black flies and horse flies are one star bugs so they can live in water that’s considered poor quality.

Sloshing around in Johnson Branch we found all of these plus shrimp, crayfish, damselflies, dragonflies, beetles and quite a few large, fresh-water mussels. Otters had broken many of the mussels. We also used test kits to check the water’s dissolved oxygen content and pH, which were at healthy levels. The final assessment was that Johnson Branch was in excellent condition.

To be most effective the program guidelines should be followed and they include reference to USGS maps and research into pollutant discharge permits. The result should be an in depth knowledge of your physical surroundings and some of the factors that affect it. To adopt a stream or to get more information contact: Chris Brown, Stream Watch Coordinator at the Delaware Nature Society, Ashland Nature Center, P.O. Box 700, Hockessin, DE 19707 (302-239-2334, ext. 36) or Pearl Burbage, Citizens Monitoring Coordinator, Watershed Assessment Section, Division of Water Resources, DNREC, 820 Silver Lake Blvd., Suite 220, Dover, DE 19904.