Nutrients and Sediment

Exceedances in sediment and nutrient water quality standards result in water quality impacts across multiple watersheds within Prince George’s County (the County). To mitigate and restore local waters, the County must identify the sources of these pollutants, measure their magnitude, and understand their impacts on local watersheds. As part of its municipal separate storm sewer systems (MS4) permit, the County monitors concentrations of total nitrogen, total phosphorus, and total suspended solids (TSS). The following watersheds within the County have U.S. Environmental Protection Agency (EPA)-approved total maximum daily loads (TMDLs) for nutrients or sediment:

Anacostia River [nitrogen, phosphorus, sediment]
Mattawoman Creek [nitrogen, phosphorus]
Piscataway Creek [sediment]
Rocky Gorge Reservoir [phosphorus]
Lower Patuxent River [sediment]
Middle Patuxent River [sediment]
Upper Patuxent River [sediment]

Nitrogen

Nitrogen is a nutrient that can enter surface waters in several ways: through runoff, as leachate from groundwater, as a result of air pollution deposition, or as a component of eroding stream banks. An ingredient in agricultural fertilizers, nitrogen stimulates crop growth terrestrially, but also does the same in aquatic environments when introduced to surface waters through stormwater runoff. Overgrowths of algae caused by excess nitrogen can lead to low levels of dissolved oxygen (DO), ultimately rendering waters incapable of supporting aquatic life. In more extreme cases, human consumption of nitrogen at levels higher than 10 milligrams per liter (mg/L) can lead to a condition called methemoglobinemia (or “blue baby” syndrome) in infants, and at levels higher than 100 mg/L can lead to taste problems and physiological distress.

Maryland does not have numeric standards for nitrogen species; however, many TMDLs identify as endpoints, which are levels of nitrogen that will maintain DO levels to support aquatic life.

Phosphorus

Phosphorus also enters surface waters by way of streambed erosion or through stormwater runoff during precipitation events. Like nitrogen, phosphorus causes overgrowths of aquatic vegetation like algae, which leads to low levels of DO and inhospitable aquatic habitats. In addition, phosphorus can be adsorbed onto sediment particles and carried with the sediment as it moves downstream. Maryland does not have numeric criteria for phosphorus.

Total Suspended Solids (TSS)

TSS refers to particles of dirt, debris, and organic matter larger than 2 microns that remain suspended in water. Exceedances in TSS can cause a turbid appearance and decrease light penetration, which impacts aquatic photosynthesis, decreases DO, and facilitates the transport of additional pollutants. TSS also affects fish and macroinvertebrate communities by clogging the gills of fish, covering streambed gravel, and ultimately causing a loss of food sources and suitable habitat. Sources of TSS include stream channel erosion, increased streamflow, land development, and terrestrial runoff. TSS concentrations in streams tend to increase with the amount of impervious surface in a watershed. More impervious surfaces send more runoff to local streams, increasing the speed and volumes in the channels, which increase rates of erosion. Channel erosion moves soil particles into the water from both the stream banks and the streambed. Much of the resulting suspended sediment generated during a stormwater runoff event can settle out in deposits as the water slows between events. Increased streamflow can resuspend those sediments and transport them downstream. Maryland does not have numeric criteria for TSS.

Dashboard Instructions

Features

Use the filter bar, located at the top right of the screen, to refine data based on water quality constituent(s), subwatershed(s), and year(s) collected. Upon clicking the themed filter box, select one or more option from the drop-down menu. Data displayed in the map and tables will then update based on selection. Please note:
- Filters from multiple themes can be selected at the same time.
- Due to the nature of the datasets, biological and stream monitoring data has been separated from the rest of the water quality constituents and is located in its own filter box (to the right of "Water Quality Constituent(s)).
Use the vertical menu bar in the upper right of the map to customize the map.
- To view the full menu and descriptions of the icons, click on the Expand icon (double arrows) at the bottom of the vertical menu (the last icon).
- To view the list of symbols and their meanings, click on the Legend icon (bullet points).
- To change the preset view, click on the Bookmarks icon (bookmark).
- To view the different map layers, click on the Layers icon (stacked boxes). Hidden layers will have crossed-out eye icons, whereas visible layers will not have an icon present.
- To change the basemap, click on the Basemap icon (four small squares) and select from the options.
To move around the map, click and hold the cursor on the map, then drag it to see different areas. To zoom in, double click on area of interest on the map. There are also Zoom in (plus symbol)/Zoom out icons (minus symbol) located at the bottom right of the map.
To reset the entire dashboard to its preset layers and features, including the map, click the Reset icon (circular arrow) located in the lower right-hand corner of the dashboard.

How to use

The map and tables (dashboard) show all available data for all water quality constituents. To select the constituents discussed above, use the filter bar to click on them. The dashboard should update automatically to show relevant monitoring stations (Station IDs) and data.

To explore the data using the map:

Zoom in on a monitoring station and click on it.
A pop up text box will appear showing a data summary for each constituent.
Use the left/right arrow icons at the top left of the pop up box to scroll through all records. Please note: Arrows are only present when the selected Station ID has data for more than one filtered constituent.
To zoom in further on the station from the pop up box, click the magnifying glass icon in the top right corner (below the Station ID name).
Zooming in on the map will also filter the list of Station IDs in the table on the top right of the dashboard to show only those stations visible in the map extent.

To explore the data using the tables:

Click a Station ID in the top table. The bottom tables will update to display all water quality records for that station. Meanwhile, the map will zoom to the location of the monitoring station. To explore data using the map, click the point on the map and follow the above instructions.