Water Quality Criteria

Although many governmental agencies, including the Maryland Department of the Environment (MDE) and the Federal Environmental Protection Agency (EPA) are involved in the many facets of protection of our waterways, few concrete values have been established by these bodies as acceptable or healthy values for the parameters noted on our charts. Dissolved oxygen, water clarity, and chlorophyll a criteria have recently been adopted by the EPA Chesapeake Bay Program, and the values in the tables below are based on those criteria. A Dissolved Oxygen level of >5.00 mg/Liter is published in the Code of Maryland Regulations as a requirement for Water Quality Criteria Specific to Designated Uses (COMAR regulation 26.08.02.03-3) such as swimming or shellfish harvesting. In addition, some parameters (e. g., pH, dissolved oxygen) may have both upper and lower criteria, as these parameters are often elevated during algal blooms due to removal of CO2 and production of O2 by rapidly growing algal populations or may be depressed due to excess respiration, typically in bottom waters. These ranges can also vary as a result of water temperature changes from summer to winter. No nitrogen and phosphorus water quality criteria have been adopted by EPA or by state agencies as criteria in Bay or estuary waters. Therefore, the criteria values for these nutrients in the charts are based primarily on scientific studies of water quality in Chesapeake Bay and elsewhere (e.g., Buchanan et al. in press, Fisher et al. 1988, 1992, 2004; Ryding and Rast 1989; Staver et al. 1996; Stevenson et al. 1993).

TRPA and the Talbot County Creekwatchers have adopted a series of water quality criteria for evaluating the data collected in Talbot County Rivers. There are two types of criteria are described below; minimally acceptable values in current samples; and desirable target values for the future. Minimally acceptable values are those, which are currently considered acceptable as water quality criteria under current conditions of land management and wastewater disposal. However, these are not stringent criteria and are only useful for indicating violations of reasonable standards of environmental stewardship. The desirable target values are water quality criteria, which TRPA and the Creekwatchers would like to see achieved in the future under better land management and advanced wastewater treatment. TRPA and Creekwatchers are accepting, as an element of their mission, achieving future test results of our water within these ranges

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Water Testing Parameters - What do they mean?

Dissolved Oxygen

Dissolved oxygen is essential to all aquatic life. When the algal blooms sink to bottom waters, oxygen is depleted as the algae decay. If the oxygen is reduced below 3 mg/ L, plants, fish and other sea life are harmed or killed or may leave the area if they are mobile. This often occurs during the summer months when nutrient pollution and algal blooms cause low dissolved oxygen levels, or hypoxia. At times, areas of our waterways may even be anoxic, which means the water is devoid of oxygen (0 mg/L). This can be characterized as the waters being "dead". When oxygen in deep water is depleted, fish and other species will die unless they move to other areas of suitable habitat.

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Water Clarity

Water clarity measures the ability of light to pass through the water. Should light not be able to penetrate the water, underwater grasses are not able to survive. Causes of poor water clarity can be excessive algal blooms or sediments from erosion. Algal blooms can become so dense that they reduce the amount of sunlight available to submerged aquatic vegetation (SAV). Without sufficient light, plants cannot photosynthesize and produce the food they need to survive. The loss of sunlight can kill the grasses. These grasses are a vital part of the aquatic ecosystem and many forms of marine life needs the aquatic vegetation for food and shelter from predators. The plants also produce oxygen. Water clarity can also be reduced by sediment entering the waters from runoffs from the land or soil erosion on the banks of the waterways. Suspended sediments make the water cloudy so less light is available for underwater grasses In addition to increasing the turbidity, sediments can also carry high concentrations of certain toxic materials that contaminate waterways and may also carry nutrients, particularly phosphorus, which increase nutrient pollution in the rivers.

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pH (Acidity)

pH levels are directly related to the health of fish and aquatic plant life in the water. In a healthy system, pH levels should be in a neutral range between 6.5 and 8.5. Levels of pH below 6.5 indicate that the water is in an acid state. The most common reason for acid water is storm water runoffs and air deposition of nitric and sulfuric acids and other toxic chemicals discharged by industries, power plants and automobiles. Toxicity depends on many factors such as concentration, chemical and physical form, and persistence of the chemical. Levels of pH greater than 8.5 usually indicate the presence of algal blooms because intense photosynthesis by algae removes CO2 from the water and increases the pH.

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Nitrogen and Phosphorus

Nutrients, like nitrogen and phosphorus, occur naturally in water, soil and air. Just as the nitrogen and phosphorus in fertilizer aids the growth of agricultural crops, both nutrients are vital to the growth of plants within the Chesapeake Bay and our Talbot County rivers and creeks. However, the main causes of the pollution of our rivers are elevated levels of these two nutrients. In addition to the natural sources of nitrogen and phosphorous, sewage treatment plants, private in ground septic systems, industries, vehicle exhaust, acid rain, and runoff from agricultural, residential and urban areas contribute nutrients to the waterways. Although plants and animals in the rivers need nutrients to live and flourish, excess nutrients become pollutants. Excess nutrients in our waterways cause rapid growth of algal blooms. These algal blooms cloud the water and reduce the amount of sunlight reaching the Bay's underwater plants and fish.

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For more detailed information on the causes and effects of pollution of our waterways, view our Creekwatchers Reports.