In this section the score for Dissolved Oxygen (DO) is relatively good. Two large tributaries, the Northwest Branch and the Northeast Branch, meet at Bladensburg to form the Anacostia River. These tributaries and their branches are free flowing, leading to turbulence that oxygenates the water.
Surprisingly, when historical data is analyzed the fecal bacteria is often worst in MD Anacostia as compared to the DC segments with Combined Sewer Overflows (CSOs) (see trend analysis for fecal bacteria). However, 2011 data shows a better score for this section. Yearly weather variation could account for some or all of this change, but also WSSC is working hard to repair damaged sewer lines in Maryland. Since this data is variable, we broke it into 5-year chunks. This section had the greatest improvement in 2006-2010 as compared to 2001-2005.
This year water clarity (Secchi Disk Depth) was very low. Stormwater volume and velocity is a serious problem in this section as about 73% of sediment in the Anacostia comes from streambank erosion. This is because we have increased volume, velocity, and frequency of peak stream flows that are a result of concentrated stormwater runoff from increased impervious surfaces like roofs, roads, and parking lots. This problem can be addressed by low-impact development or environmental site design technologies such as green roofs, rain gardens, and tree plantings that infiltrate runoff and prevent large volumes from reaching local streams.
The MD Anacostia section had the best chlorophyll (a) score of the three sections we assessed. However, the highest score does not mean that no excessive nutrients are coming from Maryland. There is a lag time between the discharge of nutrients and the uptake of nutrients by algae; the biomass of algae is related to the value of chlorophyll (a).
Overall, the grade for the MD Anacostia was B-.
Click here to download a printable version of the 2011 State of the Anacostia River.