The Potomac Conservancy has released their biennial report on the Potomac River, the second largest river draining into the Chesapeake Bay. The health of the Potomac River, due to its large area and population size within watershed boundaries, is very important to the health of the Bay. The Potomac Conservancy has issued the River a grade of B- in terms of overall health. Rising from a D to a C to a B- over the past ten years, the state of the Potomac River is improving. However, a number of different areas need to be addressed to continue to improve water quality in the Potomac and the Chesapeake.
Figures 1, 2, and 3 show changes to nitrogen, phosphorus and sediment loads in the Potomac from 1985 to 2014. Over this time period, there have been load reductions from these three major sources of pollution.
The improvements in overall health of the Potomac River are due in large part to reduced sediment and nutrient loads from agricultural activity and wastewater treatment plants.
Wastewater treatment facilities have undergone a number of upgrades to ensure that water discharged from facilities contains smaller concentrations of nitrogen and phosphorus. With higher standards now required by the EPA, upgrades to many wastewater treatment facilities in the watershed have contributed to cleaner waters in the Potomac River. (Between 2011 and 2015, there was a 13% increase in facilities adhering to stricter EPA standards).
Agriculture in the Potomac River watershed has likely contributed fewer nutrient loads because agricultural activity within the region is declining, as land is converted to accommodate urban sprawl. The Potomac River, which flows from Fairfax Stone, West Virginia to Point Lookout, Maryland, covers a large urban and suburban area. So, while agricultural runoff is decreasing, nitrogen and phosphorus loads in stormwater runoff from developed areas is still a major concern.
Within this report, the Potomac Conservancy grades a number of sub-indicators of river health, such as fish population, underwater grass abundance, and recreational use. These ratings are then examined together to determine overall health. While overall health of the river is improving, there are some areas that are actually doing worse, or showing no marked improvement from previous years. This is the case for water clarity and underwater grass abundance, which received a grade of C-. These two factors are important indicators of health in the Chesapeake Bay (underwater grasses provide food and habitat for marine species, and filter sediments and nutrients in the water, which can improve water clarity). Going forward, I would definitely like to see higher rates of recovery for these two indicators.
There is mixed news for the river’s fish populations. Certain species, such as shad, white perch, and smallmouth bass are experiencing population growth. The Bay’s rockfish population, however, has declined slightly over the past ten years. Many fish species are at continued risk of predation from invasive species such as the blue catfish and snakehead.
In terms of tidal water quality, certain conditions are improving, although numbers for dissolved oxygen, clarity, and chlorophyll A (a measure of algae), vary year to year. Chlorophyll A levels have declined over the last fourteen years. See Figure 4 below.
[We have been taking water samples from both the Potomac River (out of Great Falls), and Antipoison Creek, (which is just off of the Chesapeake Bay, close to where the Rappahannock River meets the Bay), and interestingly, found higher chlorophyll levels in Antipoison Creek. I’ll post more on our results later.]
There was good news for recreational land use, which has gone up since the last report. Recreational use of waterways can be an indicator of improved water quality.
Protected land area has increased, from 1.8 million acres in 2011 to 1.9 million acres in 2013. This area equates to 26.6 percent of land in the Potomac River watershed.
Concerns going forward include rates of deforestation and development in unsuitable areas, and runoff from suburban and urban regions. Agricultural areas, while declining, could still do with the enforcement of Best Management Practices (BMPs). The amount of forested buffers (streamside vegetation which reduces agricultural runoff into tributaries), received a grade of C-.
It’s important to keep in mind that the results in this report do not come from the most current data. The Potomac Conservancy gathers its information from a number of institutions, such as the EPA and the USGS. There is a couple years lag time on data for many of these sub-indicators of overall health.
Information and graph source: State of the Nation’s River 2016, Potomac River Conservancy, http://potomacreportcard.org.