WATER QUALITY MONITORING PROGRAM
Much of the water flowing through Flat Rock Brook comes from runoff of rainfall and snow melt throughout the surrounding suburban developments. We are monitoring the following water characteristics to help people understand the impact they can have on aquatic ecosystems, to identify specific problems, and to work towards solutions of those problems. We regularly sample water from several locations along Flat Rock Brook, including both the northern and southern tributaries upstream from McFaddens Wetland, and in the stream at the picnic area along Jones Road.
Nitrate and phosphate are plant nutrients that can come from fertilizers, detergents and animal waste. High levels in streams and ponds can cause excess growth of algae, which can lead to murky water and a loss of oxygen as the dead algae decomposes. Nitrate and phosphate are measured in parts per million (ppm). Unpolluted waters generally have nitrate levels less than 1 ppm, and phosphate levels less than 0.1 ppm.
Dissolved Oxygen in the water is required by all animal life, ranging from fish to insect larva to microorganisms. The diversity of organisms in the water drops significantly if dissolved oxygen levels are too low. D.O. comes from diffusion from the atmosphere (increased by waterfalls and rapids) and from living plants doing photosynthesis. Low dissolved oxygen can result from too much dead organic matter in the water, as the decomposing bacteria consuming this organic matter use up much of the oxygen. D.O. is measured in parts per million. Levels below 6 ppm cause problems for many organisms.
Turbidity is a measure of the lack of clarity of water due to suspended solid matter. Turbid or cloudy water, possibly caused by runoff of sediment from erosion or excess algae growth, blocks sunlight needed by submerged vegetation. Particles can interfere with gills in fish and invertebrates. The particles causing the turbidity eventually settle to the bottom, covering the natural gravel material required by organisms, and in the long term causing bodies of water to completely fill in. Turbidity is measured in Jackson Turbidity Units (JTU).
pH is a measure of acidity. The pH scale goes from 1 to 14. Values below 7 are acidic and values above 7 are basic. Most aquatic organisms require a fairly narrow pH range close to 7, or neutral, water. Values outside that range can affect fish, invertebrates, and microorganisms responsible for decomposition. pH levels can also cause release of toxic metals from the sediments. Acids can come from acid rain or other types of pollution.
Alkalinity is the ability of water to neutralize any added acids. Calcium carbonate is a common example. These chemicals often reflect the local geology and soil composition, and help protect the waters from the impacts of acids. Alkalinity is measured in equivalent parts per million of calcium carbonate. Alkalinity of 100 to 200 ppm can stabilize the pH level of a stream.
Salinity is a measure of the concentration of various chemical forms of salt. Runoff from road salt is one significant source of salt in fresh water ecosystems. Increased salinity can harm a wide variety of aquatic organisms, including fish and amphibians. Salinity is measured in parts per thousand (ppt). Ocean water is about 35 ppt. Freshwater streams are usually below 1 ppt.