What are 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
The acceptable values, demonstrated by the red line on the charts, are:
- Dissolved Oxygen
- A range between greater than 5.00 mg/liter to less than 10 mg/liter
- Clarity
- greater than 3 feet
- pH
- A range between greater than 6.5 and less than 8.5
- Dissolved Nitrogen
- less than 0.20 mg/liter - Samples tested before 2004
- Total Nitrogen
- less than 0.24 mg/liter - Samples tested 2004 and later
- Dissolved Phosphorus
- less than 0.05 mg/liter - Samples tested before 2004
- Total Phosphorus
- less than 0.07 mg/liter - Samples tested 2004 and later
The desirable target values, demonstrated by the yellow line on the charts, are:
- Dissolved Oxygen
- A range between greater than 6.00 mg/liter to less than 10 mg/liter
- Clarity
- greater than 6 feet
- pH
- A range between 7 and less than 8.0
- Dissolved Nitrogen
- less than 0.10 mg/liter - Samples tested before 2004
- Total Nitrogen
- less than 0.12 mg/liter - Samples tested 2004 and later
- Dissolved Phosphorus
- less than 0.03 mg/liter - Samples tested before 2004
- Total Phosphorus
- less than 0.05 mg/liter - Samples tested 2004 and later
TRPA hopes that you will find the information on this section of our website helpful and interesting. Viewers should be aware that as scientific evidence increases, criteria such as these will likely change. As they do, TRPA will be sure that our interpretation of the testing results is represented properly.
TRPA thanks the Talbot County Creekwatchers for sharing the test results with us, Dr. Tom Fisher, Professor at the Horn Point laboratory, for sharing his expertise and the other TRPA volunteers who have assisted with programming the test results into the charts that are before you. Please contact us with questions and comments.
What do these Water Testing Parameters Mean? |