2021 State of the Anacostia River Full Report

River Stays On Course to Swimmable and Fishable
2021 State of the Anacostia River Full Report
River Stays On Course to Swimmable and Fishable

Overall Water Quality Assessment

Overall Water Quality Grade: PASS

The Anacostia River’s return to swimmable and fishable is well underway with its waters receiving a passing grade for the third time in four years in the 2021 State of the River Report Card. Thanks to significant efforts by the federal and District governments to address toxics at the river bottom, the score for Toxics Remediation received its first passing grade. Despite it being the third wettest year on record, underwater grasses are strongly recovering, receiving a 100% score in the last two years, which demonstrates the resurgence of a healthy aquatic ecosystem.

SOTR Sections Map

To arrive at the overall grade for water quality in the Anacostia River, the Anacostia Watershed Society (AWS) first evaluates and grades each of three sections of the 9­ mile tidal river for the key indicators of Dissolved Oxygen, Fecal Bacteria, Water Clarity and Chlorophyll a. The three sections, shown on the map below, are the Maryland portion of the Anacostia (Section 1: MD Anacostia), the upper half of the Anacostia in the District of Columbia above the East Capitol Street Bridge (Section 2: Upper DC Anacostia), and the lower portion in the District (Section 3: Lower DC Anacostia). Assessment for Submerged Aquatic Vegetation (SAV), Stormwater Volume Runoff, Toxics, and Trash is conducted for the entire tidal Anacostia River. These parameters will also be taken into consideration to give %Score and Grade for each section and the entire river.

For the past decade, the Anacostia River made steady progress and finally received a passing grade in the 2018 State of the River Report Card.  In the 2019 report card, the grade slipped just below passing, but the overall momentum towards swimmable and fishable is evident in this year's grade. The river recovered very quickly from the damage caused by the large amount of stormwater runoff in the wettest year in the recorded history in 2018, a big reason we suspect that the grade went down.  The record-setting rains brought an increase in  pollutants to the river from impervious surfaces (roads, roofs, parking lots, etc.) and created torrential streamflows that caused streambank erosion which sent sediment to the river. All of this led to make the water cloudy and unable to support the nearly 100 acres of submerged aquatic vegetation that the Anacostia River is clearly capable of supporting now.

In 2019 (data year) the precipitation was average and the %Score for the entire river quickly recovered to 63%.  It is promising that the %Score remained at 63 in 2020 (data year) even though it was the 3rd wettest year on record.

Dissolved Oxygen (DO) had been declining  in recent years despite the implementation of the new storm tunnels in the District.  However in the MD Anacostia, the overall trend since 2012 shows signs of cautious improvement.  Fecal Bacteria %Score degraded to 46 from 60 in 2020; frequent precipitation in a wet year is likely to show fecal matter that washes into the river from impervious surfaces with more frequency.  Water Clarity slightly degraded to 49 from 52 since frequent rainfall events cause erosion along streams, adding sediment to the water.  Chlorophyll a remained the same 81.  SAV remained at 100.  Stormwater Runoff Volume degraded to 48 from 60, also due to the wet year in 2020.  Toxics Remediation improved to 61 from 55 and gained the first passing grade in that category thanks to the finalization of the Anacostia Sediement Plan and guaranteed funding for restoration work with a judgment against Monsanto for their role in polluting the region's waterways.  The Trash Reduction score improved to 64, with Prince George's County acheiving a key goal.  Overall the grade for the entire Anacostia River remained at 63 (D grade), the highest score since AWS started this assessment.

2021 SOTR 3 sections table

The above table shows %Scores for each parameter and for each section (when available).  Section 1 (MD Anacostia ) had highest %Score this year.  The %Score for the entire Anacostia was 63. The letter grade for the entire river was D, a highest grade since AWS started the SOTR assessment.

In the past, intense rain events resulted in regular sewage and runoff discharges to the DC portion of the river from the District’s Combined Sewer Overflow (CSO) system.  Though 90% of discharge was reduced thanks to the Anacostia Tunnel, this overflow still happens into the Anacostia. The largest amount of CSO discharge happens in Section 2. CSOs discharge a lot of organic matter that will later decompose, consuming oxygen in the water. As a result, dissolved oxygen values could be very low in the District portion of the river, especially in Section 2. The faster flowing, more turbulent, Maryland streams carry more DO, and give the Maryland portion of the Anacostia a better grade compared to the DC portions of the Anacostia.

In contrast, the tidal river in Maryland normally has higher readings of fecal bacteria (thus a lower score) than the lower portions in the District due in part to the presence of more wildlife feces upriver. Potomac River water that enters the lower Anacostia as part of the daily tide cycle also has a stronger dilution effect in the lower river which could be a factor here.  However, in 2020 (data year), Lower DC Anacostai had the lowest %Score (thus, the highest E. Coli. readings).  See Data Analysis for further discussion.

Signs of Improvement - Mussels

Tagged Mussel A-261

In 2018 we began our #MusselPower program to propagate mussels in the Anacostia River.  Juvenile mussels produced by our partners at a hatchery at the Virginia Fisheries and Aquatic Wildlife Center were deployed for a year in floating baskets at 8 locations in the Anacostia River. The mussels were monitored every month to account for survival and growth, then some were tagged and all the mussels were released into the river. This program continues today, and as of May 2021, the Anacostia Watershed Society has returned 19,000 native freshwater mussels to the ecosystem, and they will filter 69 million gallons a year, the equivalent of 106 Olympic-size swimming pools annually.

Pictured to the right is mussel A-261, one of the original juveniles in our 2018 program, who was re-found in in spring 2021 near Kingman Lake. This freshwater mussel has grown another 20% on its own in the wild!

Freshwater mussels are the most imperiled of all animals in the United States, a country known to have the world’s greatest diversity of this taxonomic group with over 300 species. We have identified eight species of freshwater mussels in the tidal Anacostia River: Eastern floater, Eastern elliptio, Paper pondshell, Eastern pondmussel, Tidewater mucket, Northern lance, and Eastern Lampmussel and Alewife floater. Five of those species are listed as “Species of Greatest Conservation Need” in Maryland and/or DC. Just one adult mussel can filter between 10-20 gallons of water a day! Therefore, our freshwater mussels play the same filter feeding role of the oysters, which can only grow in brackish water.  Get an in-depth look at our #MusselPower program and read the story map by clicking here.

Signs of Improvement - River Otters


Closeup of River Otter at the Tidal Basin from National Park Service photo from their April 2021 tweet

In 2016 AWS captured a photo of what we suspect to be a river otter with our trail camera, in 2017 DOEE took clear photos of the Northern River Otter at the National Arboretum, and most recently they were spotted by the National Park Service at the Tidal Basin! The Northern River Otter is a species listed as a "Species of Greatest Conservation Need" in the DC 2015 Wildlife Action Plan. The return of species like the river otter is another sign of the Anacostia River's improving health.

Signs of Improvement - Emergent Wetland Plants

Thanks to the water clarity improvement and the resident Canada Goose management by National Park Service, which started in 2016, AWS staff noticed during our routine water quality monitoring that emergent wetland plants are emerging along the river voluntarily. Normally “natural” Canada geese stay in the Anacostia area only during the late Fall and Winter.  It was human beings who created the resident Canada goose problem.  They were clipped live decoy or introduced from Minnesota and Wisconsin.  Those resident Canada geese do not migrate and had eaten wetland plants all year round.  Wetland plants had to be protected by fences in the past since those plants had been over-eaten by resident Canada Geese. Now the wetland plants are coming up voluntarily without the fences.

A map shown below illustrates that the voluntarily emerged wetland plants are spreading along the Anacostia River. Check on/off the boxes for a given year to see how wetland plants are spreading:


Comparing Year to Year

comparing year to year

There are limitations when comparing water quality scores over a short period of time because of numerous variables that impact water quality parameters. For example, more intense and frequent precipitation patterns generally make the water quality worse. More rain results in more sewer overflows and an increase in polluted runoff from streets and parking lots. So the comparison of indicators for wet and dry years can mask the underlying conditions. Long term trends are generally more helpful for understanding the river and changes in water quality than year-to-year, short term comparisons.

Despite the various weather patterns, dry weather or wet, the trend of water clarity has been improving gradually and steadily in terms of %Score though it is difficult to see the trend clearly in the year-to-year comparison in the above table (See Data Analysis to better see trend). The long term improving trend toward clearer water was also seen in the return of submerged aquatic vegetation (SAV) as reported in the 2015 Report Card for the first time since it disappeared from the Anacostia in 2003. SAV is back and continues to grow! However, the large amount of precipitation in the wettest year of 2018 made the water cloudy and the acreage of SAV bed significantly decreased in 2018 (data year). In 2019, the precipitation was average and the water clarity became better than that in 2018 and SAV is back.  The acreage of SAV in 2019 was 92.6 acres according to the DOEE SAV report published in March 2020.  Though 2020 was very wet with 57.34inches of rain, the SAV acreage remained relatively high and was 67.2 acres. The goal of SAV acreage in the Anacostia is 20 acres and it was well beyond the goal.

Again, for some parameters the improving trend is not clearly visible in the table. When we examine trends, it is very important to see a long term analysis. See our Data Analysis for detail.

The %Score calculation table for Toxics and Trash is shown below.

2020 toxics trash

AWS streamlined the scoring system in 2018 getting feedback from stakeholders.  We removed Political Will as an evaluation point because it could be evident among the other evaluation points.  We also removed Declaration of Fishable Anacostia by Governments and Declaration of Trash Fee Anacostia since we are not sure if these ever happen.  Instead, we added analysis for Fish Advisory to Toxic Remediation and Visual Assessment of the River to Trash Reduction. Since Education and Public Awareness is very important to change people’s life style to not litter, we added it to the evaluation points for Trash Reduction.

While there has been substantial progress in the study and assessment of legacy toxics in and along the river, notably the ongoing investigation of toxic river sediments throughout the entire tidal portion of the river, and continued collaboration and discussions among stakeholders and potentially responsible parties, little actual cleanup regarding the toxic sediment in the river has yet to occur. The only sites along the river that have completed cleanups are Washington Gas and the Washington Navy Yard, CSX Benning Yard but these were on land only.  However, the river portion (sediment) study is coming close to completion and the interim Record of Decision on the toxic sediment happened in September 2020.  The score for Funding improved significantly reflecting that the DC government reached a settlement in July 2020 that held Monsanto accountable for polluting the District’s environment with PCB and Monsanto will pay $52 million to the district.  Until there is a reduction in the presence of toxic substances in and along the river that results in an improvement in water quality and the health of aquatic organisms, the score/grade for Toxic Remediation will remain low.  However, the Toxic Remediation evaluation has received the first passing grade in the 2021 State of the River Report!

Though the %Score for Toxics Remediation is still low, kudos must go to the Department of Energy and Environment (DOEE).  The %Score increased from 0 (in 1989) to 61 (in 2011) thanks to the strong leadership and investomen by DOEE.  Without their work, this improvement would have not happened. 

Progress on trash reduction has been slow, but growing. Past efforts to install trash traps in the District and charge fees on plastic bags in DC and Montgomery County are notable. Stepped up efforts by local jurisdictions to reach goals set in trash reduction plans required by federal law (due to the extreme nature of the problem here) should soon produce more substantial results. This includes new laws to prohibit the use of plastic foam (a.k.a. Styrofoam) as food and beverage containers (effective January 1, 2016 in the District and Montgomery County, and July 1, 2016 in Prince George’s County). The proliferation of beverage containers in river trash is a major problem yet to be addressed. Environmental advocates have started to take action to reduce beverage containers through legislation; however, these efforts have been unsuccessful thus far. Non-floatable trash is also a significant problem; AWS trash monitoring at Nash Run shows about 70% of trash by count is non-­floatable. More work needs to be done to address this larger problem likely through enforcement of illegal dumping and littering or lifestyle and landscape change. Our food packing lifestyle could be changed so that food wrappers (chip bags, etc.) will not be discarded.  Our landscape has been slowly changing to infiltrate stormwater into the ground. It is stormwater runoff that carries trash to streams. In the long run the landscape change will help reduce trash in streams significantly.

Data Analysis

Dissolved Oxygen


The amount of dissolved oxygen (DO) has been steadily improving in all three sections of the river except in recent years. DO values have been low recently and the %Score, as a result, has been low. The sharp drop in 2013 seems to be because of weather patterns that was not favorable to DO. There were many intense rainfall events that regularly caused Combined Sewer Overflow events in downstream DC in 2013. The CSO events dump raw sewage mixed with rainwater into the river when it rains heavily. The discharge includes organic matter which will later be decomposed by bacteria. The decomposition consumes oxygen in the water. See the example graph below that shows how DO changes in an intense rainfall.

2019 DO detail

Because the CSO discharge is churned up, the discharge itself has high DO values. As the time passes by, decomposition will proceed and it consumes oxygen in the water resulting in prolonged low DO values.

It seemed that this was not the case in 2018.  According to DC Water, 90% of CSO discharge was captured and sent to Blue Plain thanks to the Anacostia Tunnel System.  And a lot of rain in 2018 brought DO-rich water into the tidal Anacostia resulting the higher %Score in 2018.

Very dry weather also reduces the amount of oxygen especially in a tidal river.  Rainfalls with moderate intensity with no CSO events will bring oxygen-rich water into the tidal river.  Without these oxygen supply during very dry weather, the amount of oxygen tends to become low.

Because the MD Anacostia (Section 1) receives oxygen-rich water from two large tributaries -- the Northwest and the Northeast Branches -- DO tends to be higher than in the DC portion (green and purple line/dots in the graph).  AWS reported on the DO decline of unknown origin appearing since 2009 when CSO overflow reduction started and presented three hypotheses of the reduction.  In 2020, a sign of improvement could be seen in the MD Anacostia.  This is consistent with our river observation, but we are cautious about the improvement until we see longer term results.  The muddy river shore is becoming sandier, which indicates that the river shore may be getting oxidized.

DC Water (formerly DC WASA) broke ground in October 2011 on the $2.6 billion Clean Rivers Project (CSO Long Term Control Plan) to control sewer overflows. The Blue Plains and Anacostia River Tunnels came online in March 2018.  DC Water reported in March 2019 that the tunnels reduced 90% of the combined sewer overflows to the Anacostia River. Further, the project will reduce combined sewer overflows by 98 percent at completion in 2022. 

Fecal Bacteria

Ecocheck EColi 2020

Many Anacostia watershed residents know of the Combined Sewer Overflow problem in DC. The sewer system in DC was designed to overflow into the river when a rain event exceeds approximately a half inch. However, contrary to public perception, downstream DC water is cleaner than the upstream MD water in the Anacostia in terms of fecal bacteria. There are two possible reasons that might account for this: (1) the tidal action washes the mouth of the Anacostia with much cleaner Potomac River water twice a day, and (2) there is a large amount of fecal matter input from Maryland. Washington Suburban Sanitary Commission (WSSC) in Maryland and DC Water are working to repair sewer leaks and implement remediation projects to reduce sewer overflows. However, there is quite a large uncontrolled portion of fecal matter from wildlife.

According to a study conducted by AWS and Charles Hagedorn of Virginia Tech University, funded in part by Chesapeake Bay Trust (CBT), approximately 70 percent of fecal bacteria from Maryland is attributed to wildlife. Approximately 7-8 % of fecal bacteria is from canine. Feces excreted on impervious surfaces by birds, squirrels, raccoons, deer, mice, rats, etc. is washed away by rainfall and is carried into streams. Though the largest source of fecal bacteria may be wildlife, its transport to the river is caused by the impervious surfaces we have created. In natural settings, wildlife feces tend to decompose on site and most rainwater infiltrates into the ground and will not cause fecal bacteria pollution in streams.

All river sections show steady improvement over the years with the District portions improving faster. In 2018 all sections significantly degraded from the previous year. On average the score for the entire Anacostia became worse from 62 in 2017 to 39 in 2018). This significant decline is due to heavy rainfall in 2018 (the wettest year in the recorded history). Stormwater runoff carried a lot of fecal matter to the river. The year of 2019 had an average amount of precipitation. Stormwater runoff inputs to the river weresmaller than that in 2018. Thus, %Score increased to 60 in 2019 from 39 in 2018.  For this report card, it was the 3rd wettest year since 1984; thus the %Scores for all jurisdictions in 2020 became worse. 

Water Clarity (Secchi Disk Depth)

Secchi Solo 2019

In the graph above, the trend line (not the scatter plots) is the average value of scores for the past five years. This method clearly illustrates the trend.

Water clarity indicator (Secchi Disk Depth) has been low for all sections in all years for which data is available.  However, since CSO discharge reduction started in 2009, the %Scores in all sections have been steadily increasing till 2017 though it became worse in 2018 due to the wettest year of 2018.  Lower DC Anacostia had highest %Score of 59% in 2016.

From 2001 until 2009 water clarity in Maryland and Upper DC (Sections 1 and 2) had been declining. The best average score for these sections was in 2001. Since then, the average has been declining until recently. In the Lower DC Anacostia (Section 3) the best average score was in 1995. Since then the average was declining until about 2006. However, thanks to the CSO overflow reduction started in 2009 water clarity in all sections has been improving steadily. Responding to the recent water clarity improvement, submerged aquatic vegetation (SAV) reappeared in 2013 after being absent from the Anacostia River for ten years. (See the trend analysis for SAV below for details.)

In order to accelerate water clarity improvement, stringent regulations on stormwater runoff should be implemented because the increased peak stream flows resulting from flashy stormwater runoff from increased impervious surfaces have been eroding the streambanks and scouring streambeds, making the water cloudy.

According to a study conducted for the Total Maximum Daily Loads (TMDL) for sediment, about 73% of sediment is coming from streambank erosion. The study was conducted for suspended sediment particles in the water. When heavier particles of sediment are taken into consideration, it is safe to say that more than 73% of sediment is coming from streambank erosion.

Water Clarity has been responding to the CSO reduction very well. In 2009 CSO was reduced by 40%. Upper DC Anacostia, where it receives the largest amount of sewage from CSO, responded to it immediately in 2010. In 2011 CSO was reduced by 60%. Responding to the reduction, Water Clarity in, especially, Upper DC Anacostia has been rapidly improving.

The year of 2020 was the 3rd wettest year and the %Score declined a little from the previous year.  However, the trend shows the clear improvement.



Chlorophyll is the green pigment of plants that converts sunlight into organic compounds during photosynthesis. There are seven known types of chlorophyll; Chlorophyll a and Chlorophyll b are the two most common forms. Chlorophyll a is used as a measure of microalgae biomass, which is controlled by factors such as water temperature, light, and nutrient availability. Too much algae leads to large algal blooms that can reduce water clarity. Also, once an algae bloom dies, it depletes water of oxygen when it is decomposed.

%Scores for Chlorophyll a has been improving.  It improved even in the wettest year of 2018.  The %Score in 2019 was the same as that in 2018. The overall better score in Maryland (Section 1) does not mean that there are no excessive nutrients coming from Maryland. Because Chlorophyll a is a green pigment in plants, algae, and cyanobacteria, it does not accurately reflect the nutrient amounts in water. There is a lag time between discharge of nutrients and their uptake by plants, etc.

In the free-flowing tributaries of the Anacostia, discharged nutrients travel to the tidal Anacostia. Because the tidal river moves slowly, there is plenty of time for microalgae to take up nutrients. Thanks also to the ample sunlight for photosynthesis in the tidal Anacostia, the DC portions of the river (Section 2 and Section 3) tend to have higher Chlorophyll a values, resulting in lower scores. Both upstream and downstream communities need to stop stormwater runoff that convey nutrients (fertilizer, for example) from properties.

The %Score of Chlorophyll a in 2018 was highest even though 2018 was the wettest year in recorded history.  This is probably thanks to the Anacostia Tunnel being operated from March 2018. The tunnel reduced 90% of CSO discharge.  Also, the water was cloudier in 2018 that supressed photosynthesis for algae to grow.

It is very interesting to see the DC sections (Sections 2 and 3) had been better than the MD section (Section 1) in 2013, 2014, and 2019. Also, DC Anacostia is improving faster than MD Anacostia judging from the inclination of the regression lines.

Submerged Aquatic Vegetation (SAV)


SAV data source until 2016: http://web.vims.edu/bio/sav/index.html Starting this year, AWS is using DOEE data because DOEE does an accurate on-the-ground survey. The data for 2018 is preliminary and this score may be adjusted later.

Submerged Aquatic Vegetation (SAV) are plants that cannot withstand excessive drying and therefore live with their leaves at or below the water surface. Such vegetation constitutes an important habitat for young fish and other aquatic organisms.

AWS's goal for restoring SAV in the Anacostia is 20 acres, a goal identified in the Anacostia Watershed Restoration Indicators and Targets for Period 2001 ­- 2010 by scientists at Metropolitan Washington Council of Governments (COG).

In the graph as soon as the degradation of water clarity in the Lower DC Anacostia (Section 3) was observed in 1995, the acreage of SAV started to decline. No SAV had been observed in the Anacostia since 2003 until 2012, the score for the time duration had been zero (0) for over a decade. While there was no SAV in the tidal Anacostia, it is known that there has been SAV in non­tidal tributaries to the Anacostia River.

However, in 2013, 0.9 acres of SAV (thus, the %Score is approximately 5% ­­ 0.9/20x100) was identified in Washington Channel and we learned that SAV is coming back to the Anacostia River!

AWS is not certain why SAV was present in the past --particularly in the 1980s and 1990s when the water clarity seemed worse than or equal to the current clarity. However, we have several hypotheses:

      • The nature of the cloudiness of the water was different. There are many factors that make the water cloudy. Recent cloudiness may be a complex combination of sediment particles due to erosion, decaying organic matter from sewage, algae bloom, etc. while past cloudiness may have mainly come from sediment particles.
      • The river was monitored less often in the 1980s and 1990s. The water quality data may then be less reliable during the time period.
      • The SAV may have suffered in the 1980s and 1990s, but may still have been resilient to the pollution.
      • The overall nature of pollution may have changed. In more recent years, numerous types of pollutants including chemicals such as pharmaceuticals, pesticides, herbicides, and heavy metals on top of water cloudiness may have helped eliminate the plants.

In 2017 the SAV coverage in the Anacostia River became 24.71 acres.  This is over the goal of 20 acres and the %Score for SAV is 100%.  In 2018, the wettest year in the recorded history, the acreage of SAV receded.  However, in 2019 when the precipitation was average, SAV grew significantly and the acreage was 92.6 acres (over 20 = 100%). In 2020, SAV showed resilience even though 2020 was the 3rd wettest year.  The Anacostia had 67.2 acres of SAV bed.

Stormwater Runoff Volume

Northwest Branch


Northeast Branch


From the data, we see that the %Scores of Stormwater Runoff Volume for the NW and NE Branches became static, even slightly improving in recent years, starting in 2007.  We might be seeing a positive response from the Maryland Stormwater Management Act of 2007, which AWS helped pass.  Under the act, all new developments have to treat precipitation of a 1-year rainfall event (2.7 inches).  The act also requires that re-development has to be designed to treat a certain amount of precipitation which amount is different by jurisdiction.  However, when we see the graphs, there is an improvement-degradation cycle every approx. 30 years.  Thus, we need to see the trend for a longer time to see if it is improving in recent years or if it is only a cycle.

Assessment Methods

To evaluate the data for the State of the River report card, the Anacostia Watershed Society employs a variety of scientific methods. Currently there is not a standard grading system to assess Stormwater Runoff Volume, Toxics, and Trash.  These factors are very important to the health of the Anacostia River, so we created our own method, and we explain our scientific process here.

Water Quality Indicators

The EcoCheck method developed by the Mid-Atlantic Tributary Assessment Coalition was used to assess the river for water quality parameters as described under the Data Analysis section above: Dissolved Oxygen, Fecal Bacteria, Chlorophyll a, Secchi Disk Depth (Water Clarity), and Submerged Aquatic Vegetation (SAV).

The link to the manual is here (pdf file, 8.3 MB).

Though AWS uses the EcoCheck protocol to calculate the %Scores for the water quality parameters, unlike other years, in 2014 and beyond AWS did not use the manual’s grading system (A through D and F) because it employs equal interval breaks for grading. Feedback from the public indicated that the EcoCheck grading system is confusing because of its similarity to a school grading system while the interval breaks are different. The EcoCheck grading of C (>=40 and <60 by the EchoCheck %Score) indicates the river is given a passing grade for a swimmable and fishable, but in actuality it is not). In order to make our grading more understandable and relatable to the general public, in 2014 and beyond, AWS is using a school grading system for the State of the Anacostia River Report.

Stormwater Runoff Volume

Initially, AWS wanted to measure the areas of impervious surfaces throughout the watershed. However, measuring impervious surfaces had various difficulties:

      • AWS relies on government data which is not released on a regular schedule.
      • There are several methods to calculate imperviousness that produce different results.
      • There are 3 jurisdictions in the Anacostia watershed and they do not all use the same methods for calculations.
      • Green infrastructure is continuously being installed and each technique/practice has a different capacity to manage stormwater. It is not clear how those differences will be taken into account as pervious surfaces.

Because of those factors, AWS decided to use peak streamflow data for the Stormwater Runoff Volume analysis because the excessive runoff is generated by impervious surfaces, which will generate sharper peak streamflows when it rains. It is not practical to measure the volume of stormwater runoff. However, the runoff will be concentrated in streams and it is known that peak stream discharges (flows) have been increasing. United States Geological Survey (USGS) has been measuring stream discharge since 1938 in the Northwest and the Northeast Branches of the Anacostia River. The historic data was used to calculate the Stormwater Runoff Volume %score.

First, the 99th percentile of daily stream discharge was calculated for each year. Then, the values were plotted on a graph as shown below. The reason we use the 99th percentile is to eliminate values from most extreme events such as hurricanes. Using a 99th percentile value for a given year, the highest values for about 4 days will be dropped out.

2021 stormwater volume

An average of 99th percentile daily stream discharges for the years 1938 to 1941 and that for 2008 to 2012 were calculated respectively. The former is a tentative target for a 99th percentile peak stream discharge. Because we did not want to have negative values, the average for 2008-2012 was multiplied by 1.5 for use as a baseline. From this baseline of peak stream discharge, we can determine the amount of stream discharge to be reduced (B in the graph).

The tentative goal is still reasonable because in the period of 1938 - 1941, there is documentation of people who swam in the Anacostia River. However, we know that the Anacostia River had been degrading long before then due mainly to agricultural activities, sewage influx, and dumping. As we learn more, we may revise the goal in the future.

The score was then calculated using the target and the baseline.

For example, the 99th percentile peak stream discharge in a given year is indicated as “A” in the graph. Then the score was calculated using this formula:

%Score = (Baseline (current x 1.5 in the graph) - A) / B x 100

With highly fluctuating annual values, to keep an accurate assessment, AWS used 5-year moving averages. The score for 2012 is actually an average of scores from 2008 through 2012. The scores were calculated for the Northwest and the Northeast Branches and the average value was used for the Anacostia River's score for Stormwater Runoff Volume.

Toxics Remediation and Trash Reduction

Calculating the score for Toxics and Trash is very difficult due to the complexity of assessing a wide range of factors. There are many toxic chemicals in the river such as pharmaceuticals, PCB, PAH, pesticide, herbicide, and heavy metals, to name a few. There are about 200 congeners of PCB and numerous chemicals in the group of Polycyclic Aromatic Hydrocarbons (PAHs). The standard toxicity level is different for each chemical. In addition, there are chemicals that even do not have a safe standard for humans and wildlife. Quantifying the amount of trash in the Anacostia River watershed accurately each year is also very difficult, even though unlike chemicals, you can see it plainly with the naked eye!

All of these challenges make interpreting the data and comparing it to a scientifically rigorous standard in a reasonable manner nearly impossible.

Therefore, the Anacostia Watershed Society decided to take a different approach from strictly scientific scoring. AWS decided to apply the Business Confidence Index method to these important parameters. We listed actions to be taken for Toxics and Trash. Then, AWS professionals discussed how much work had been done for each action. It is like an Environmental Confidence Index for Toxics and Trash.

This method produces reasonably understandable and intuitive scores. Also this method gives a good sense to the public about what actions should be taken and where we are to remedy the problems. We will continue to monitor the accuracy of this method, and the system will receive improvements as fit.

The table calculating our scores for Toxics and Trash is shown below.

2021 toxics trash


The Anacostia Watershed Society would like to thank the following organizations for technical assistance and/or funding for this report card:

Thanks also to the AWS staff and consultants who contributed to the report:

    • Masaya Maeda, Water Quality Specialist
    • Maureen Farrington, Marketing Manager
    • Emily Conrad, Director of Development
    • Ariel Trahan, Director of River Restoration Programs
    • Reyna Askew, Manager of Community-Based Restoration
    • Jorge Bogantes Montero, Natural Resources Specialist
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