Watershed Monitoring

Monitoring in the County

The County’s monitoring program

The County has managed and participated in several long-term monitoring programs over the last three decades. From 1994 to early 2007, the County maintained and sampled at two stations in the Beaverdam Creek watershed. In 2007, with MDE approval, the County moved its biological, chemical, and physical monitoring stations to the Bear Branch watershed, where the County initiated restoration and improvement efforts to be able to better assess its watershed improvement and restoration activities. This monitoring ended in 2025.

Since 1999, the County has been conducting countywide biological monitoring and assessment of streams and watersheds. Sampling and analysis include sampling individual stream locations for benthic macroinvertebrates, physical habitat quality, and in situ water quality (pH, conductivity, temperature, and dissolved oxygen). Site assessments are performed using the biological indicators calibrated by and included in the Maryland Department of Natural Resources’ (DNR’s) Maryland Biological Stream Survey (MBSS) protocol. The County uses a comprehensive quality control (QC) framework to ensure its assessments include only data of known and acceptable quality. Each year, the County shares collected biological data with DNR and MDE, who use it to update Maryland’s Integrated Report (IR) of Surface Water Quality, which they then submit to the EPA. Information related to the Water Quality Assessment Report or IR can be found here.

The following webpages highlight monitoring data the County collected to meet MS4 permit requirements or support the total maximum daily load (TMDL) restoration program.

• Nutrients and sediment: For the past 30 years, the County has monitored nitrogen, phosphorus, and sediment, which have been a core monitoring requirement under the County’s MS4 permit. These pollutants are the focus of the Chesapeake Bay TMDL and several local TMDLs.
• Other pollutants:
  • Bacteria: A long-term requirement of the County’s MS4 permit, bacteria monitoring has recently become the focus of a comprehensive trackdown study to identify and eliminate sources of bacteria in the watersheds. There are three watersheds with bacteria TMDLs in the County.
  • Polychlorinated Biphenyls (PCBs): The focus of current trackdown studies is on identifying and eliminating sources of PCBs in the environment. There are several watersheds with PCB TMDLs in the County.
  • Chloride: The County has performed monitoring of existing chloride intensities to provide a baseline of chloride concentrations. Excess chloride is mostly a condition resulting from the application of winter deicing products used for snow removal operations on sidewalks and roads for both commercial and residential uses. The 2022 MS4 permit requires the County to develop a salt management plan for the use of winter weather deicing and anti-icing materials. While there are water quality impairments in the County for chloride, there are no chloride TMDLs in the County.
  • Trash: Trash reduction is a required part of the County’s MS4 permit. There is a trash TMDL for the Anacostia River watershed.
  • Microplastics: Although monitoring this pollutant does not fall under MS4 permit requirements or a TMDL, in 2025, the County began monitoring microplastics to stay ahead of potential future monitoring requirements.
• Biological monitoring: A requirement under the MS4 permit for many years, the County uses biological monitoring to assess the overall water quality in a watershed, to identify problem areas, and to track watershed restoration progress.
• Geomorphic (stream channel) monitoring: The MS4 permit requires the County to monitor a single stream in its jurisdiction. To better address stream erosion, the County has expanded its monitoring to multiple locations across the county to help it identify stream erosion issues and the potential for upstream solutions.

Data Quality Assurance and Control

The County prioritizes high quality data to guide restoration projects and to track program progress. All County-led monitoring is conducted by trained and experienced scientific staff under project-specific quality assurance project plans (QAPPs), which detail quality procedures, objectives, and standard operating procedures (SOPs) to ensure accurate and reliable data collection.

Under its water quality monitoring programs, the County:

• Uses a Maryland State Certified Water Quality Laboratory to process samples.
• Follows all the applicable quality assurance (QA)/QC procedures.
• Adheres to EPA-approved analytical methods.

Under its biological and stream channel monitoring programs, the County:

• Ensures that field and laboratory staff are trained and certified by the DNR’s MBSS.
• Adheres to benthic taxonomic identifications, which are executed by subcontracted laboratories staffed with taxonomists who are certified by the Society of Freshwater Sciences’ Taxonomic Certification Program.