Water quality indicators
From SDCK Watershed Wiki
Contents |
Alkalinity
This indicator is a measure of the river's ability to neutralize acid inputs from precipitation or discharges. Rivers with low alkalinity are subject to great fluctuations in pH that disrupt aquatic life. EPA resource
Bacteria
Certain types of bacteria are used as indicators of water contamination by fecal material ('poop'). These bacteria may indicate water contamination by sewage, animal or bird waste. Human and non-human sources of feces contain harmful bacteria, viruses, and protozoa (pathogens) that can cause illness in people who are exposed to contaminated water. Unfortunately, the indicator bacteria also have naturally occuring sources (soils, decaying vegetation) that do not present a risk to human health. Future research by Coastkeeper will include microbial source tracking of bacteria levels in beach waters to better determine the health risk when sample results violate state health standards.
The preferred indicator bacteria for fresh water is Escheria coli (E. coli) or fecal coliform. Enterococci is the preferred indicator bacteria in salt water, however routine beach water samples are tested for total coliform, fecal coliform, and enterococci. The state health standards for these bacteria in beach water are: Total Coliform 10,000 /100mL. Fecal Coliform 400 / 100 mL. Enterococci 104 / 100 mL. When beach water samples violate these standards, the County Dept of Environmental Health (DEH) may issue a water contact advisory. DEH issues a preemptive closure when it has a report of a sewage spill that may impact a beach.
For inland fresh water REC1 designated areas, Coastkeeper compares sample results against US EPA criteria for moderately used freshwater areas (CFR Vol. 51, No. 45/ 1986). These levels are:
E. Coli 406 / 100mL.
Enterococci 108 / 100mL. There is no regulatory requirement for DEH to warn the public when bacterial levels in inland fresh waters violate these standards. Volunteer monitoring by citizens trained by Coastkeeper provides an assessment of water quality in our creeks and streams before this water reaches the coast.
Conductivity
Water contains various natural and human-introduced inorganic materials that have the ability to pass an electric current. Conductivity measures the ability of the particles in the water to transfer electricity. It is used as an indicator of the presence of chlorides, nitrates, sulfates and phosphate anions (negatively charged ions) and sodium, magnesium, calcium, iron and aluminum cations (positively charged ions). If a conductivity level is high, it indicates a potential problem from these materials. Conductivity readings are also high where there is tidal intrusion or influence, which is often the case at lagoon and estuary sites. We monitor during low tide at these sites to minimize the influence of seawater on our samples.
Dissolved Oxygen (DO)
Water contains oxygen in the form of dissolved gas. In order to breathe, aquatic organisms - both plants and animals - access the dissolved oxygen in the water. All organisms have an optimal range of DO, and some require very high levels to flourish. Low DO levels can indicate pollution.
pH
The acidity of water is measured on a scale of 0 to 14 pH units. pH is measured using a logarithmic scale. Acidity determines the rate of many biochemical reactions in the water, and aquatic organisms have an optimal pH for functioning.
Nitrates
Nitrogen is an essential nutrient for plant and animal life. Nitrate is the form of nitrogen that is regularly available for use by aquatic plants. In saltwater streams, nitrate is usually the nutrient in shortest supply (limiting nutrient), causing a large impact on aquatic plant growth when added. It can be an indicator of fertilizer run-off, sewage, animal manure, and other types of contamination. Under certain circumstances, nitrates are toxic to aquatic life and nutrients.
Phosphates
Phosphorous is an essential plant and animal nutrient that can cause rapid increases in biological activity when levels are excessively high. Excessive plant growth due to high phopshorous levels may disrupt the ecological integrity of a stream. Phosphate is the form of phosphorous that is readily available for use by aquatic plants. In freshwater streams, relatively small amounts of phosphate can have a significant impact because it is often the limiting nutrient in the system. It can be an indicator of fertilizer, sewage, animal manure, amongst others.
Ammonia
Ammonia is often found in areas with agricultural runoff and largely exists as ammonium (NH4+) in aqueous solutions at pH = 7. As a solution becomes more basic (pH~9-10) the equilibrium shifts towards gaseous ammonia (NH3) which is more toxic. Regions with high pH and high ammonia can create conditions that are deadly for aquatic organisms.
Physical River Characteristics
The physical condition of the stream or river and the surrounding land is linked to the quality of stream habitat and water quality. Physical conditions that are observed and measured include: air & water temperature, width, depth, stream velocity, odor, appearance / color, surrounding land uses, stream bank vegetation, river bottom composition and overhead canopy.
Temperature
This is the basline indicator that determines the rate of many biochemical reactions in the waterbody and responds to certain types of land and water use.EPA resource
Trash
Debris on streets ends up in local creeks, streams and rivers and eventually ends up on beaches and in the ocean. Trash is most closely linked with bacteria, and has a negative impact on habitat, stream ecology and recreation.
Turbidity
This is a physical indicator of water clarity, measured by the extent to which light penetrates the water column and reaches the bottom. Light is essential for plant growth, and is closely linked to water temperature. In our region, high turbidity is often a result of suspended materials in the water resulting from construction activity, power washing, or urban run-off.
Toxicity
Pollutants in the water can be harmful to the organisms that depend on it. Toxicity testing is a non-specific indicator of overall aquatic health. Bioluminescent flagellates are used to assess the overall toxicity of the stream. They are added to a sample of the water and allowed to grow, or die. Light output from samples is compared against control to determine if there is inhibition in sample, likely due to toxicity.
