Rock Creek Assessment

Water Quality Monitoring
Biological Survey
Benthic Macroinvertebrates
When a stream is healthy, a large diversity of living organisms is present including mayflies (photo 3), stoneflies (photo 2) and caddisflies (photo 1). These benthic macroinvertebrates, stream bottom dwelling organisms without a backbone that can be seen with the unaided eye, are sensitive to pollution. Their presence in numbers and variety are an indicator of good water quality. Conversely, their absence can indicate poor water quality. A biological survey was performed once in the Fall of 2005 and again in the Spring of 2006. The Environmental Alliance for Senior Involvement protocol was used for macroinvertebrates sampling. A macroinvertebrate survey of the Rock Creek Watershed indicated fair to good water quality.

click to enlarge map of macro survey results

Coliforms are a broad class of bacteria found in our environment, including feces from warm blooded animals including humans. Human and animal wastes are a primary source of bacteria in water. Sources of bacterial contamination include runoff from pastures, dog runs, and other land areas where animal wastes are deposited. Other sources of contamination include malfunctioning septic systems and sewage treatment facilities. A bacteriological survey of coliforms was performed in the Fall of 2005. 10 of the 11 sites were sampled 3 times over the course of a two week period utilizing the Coliscan EasygelŪ method. Small samples of water were added to a Petri dish with a culture medium. Colonies of bacteria were allowed to form and depending on the bacteria and the enzyme(s) it produced, caused the medium to change colors. Pink dots indicate coliform colonies. Purple dots (which may difficult to see in photo left) are E. coli colonies. Blue and white colonies indicate other bacteria and molds. Coliforms were present at every site tested.

Habitat Survey

Some of the physical characteristics of a stream that indicate good quality are stable banks with a wide forested area, or riparian buffer next to the stream. Another physical indicator of good water quality would be the absence of dams and other barriers to fish. A modified rapid bio-assessment protocol was used.

click to enlarge habitat survey results