2018 State of the Anacostia River Full Report

Passing Grade
2018 State of the Anacostia River Full Report
Passing Grade

We regularly provide a progress update on the Anacostia River in part to create accountability for decision makers entrusted with the health of the river. This report card is your guide to how well our communities, environmental groups, and governments are meeting the goal of a fishable and swimmable Anacostia River, per the terms of the Clean Water Act. Provided here is a summary of the scientific data we have analyzed so that citizens and public officials can better understand the current state of the Anacostia River.

Our 2018 Report Card receives a passing grade of D-, led by the incredible regrowth of submerged aquatic vegetation (SAV).

Click here to view the 2018 State of the River Report Card Summary (pdf)

Click here to jump to the full report

Our Mission

The mission of the Anacostia Watershed Society is to protect and restore the Anacostia River and its watershed communities by cleaning the water, recovering the shores, and honoring the heritage. We believe that by working together with businesses, governments, faith-based organizations, and youth we can create sustainable solutions that improve our communities, empower our residents, and create economic prosperity that will result in a clean river. We want to change the way people think about the Anacostia and make the river a destination.

Challenges to Overcome

The most important parameters for a swimmable and fishable Anacostia River are fecal bacteria, toxics, trash, and uncontrolled stormwater. High fecal bacteria levels indicate that the water contains many types of disease-causing viruses, bacteria, and protozoa that can be hazardous to human health. We don't yet know the specific health risks associated with occasional exposure to the toxics (heavy metals, pesticides, and other chemicals) in the sediment in the river, but we do know that those contaminants are having a negative impact on fish populations and that removing or treating toxic sediment will be necessary for the river to sustain healthy fish safe for human consumption. Stormwater runoff is a major issue because runoff from impervious surfaces (e.g., roads, parking lots, driveways, roofs) brings numerous pollutants to streams and generates torrential stream flow, which causes streambank erosion and makes the water cloudy and inundates the river with sediment. The runoff also carries fecal matter, trash, and other pollutants to the river.

Data Sources and Disclaimers
  • Data set: All available, professionally collected data was used. The data sets include those collected by DC government, Maryland Department of Natural Resources, United States Geological Survey, and the Anacostia Watershed Society.
  • The data was compared with thresholds developed by Mid-Atlantic Tributary Assessment Coalition (MTAC) who created EcoCheck protocols - Sampling and data analysis protocols for Mid-Atlantic tidal tributary indicators.
  • For the 2017 State of the Anacostia River Report, a 2015 data set was used because it was the most recent available data set at time of analysis. However, assessment for Stormwater, Toxics, Trash, and Overall Effort and Commitment is for 2016.
  • For trend analysis, data sets from 1984 to 2014 or 2015 were used depending on the parameter and the section of the river.​
  • Note that no Report Card was issued in 2013 and that the one issued prior to that was dated 2011 (for the year representing most of the available data, rather than the year it was issued, 2012.)

Overall Water Quality Assessment

Overall Water Quality Grade: Pass

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.

Steady progress overall is seen once again for this year’s report with a significant increase in the %Score. Dry weather in 2016 (data year) also helped improved the score well.  Fecal Bacteria, Water Clarity and Chlorophyll a had a good improvement, likely a result of DC Water’s work to reduce its sewage overflows (reduced by 40% in 2009 and by 60% in 2011) and the dry weather in 2016 (data year). Submerged Aquatic Vegetation (SAV) achieved the goal of 20 acre coverage in the Anacostia River (Note: AWS used DOEE data for SAV from 2017 because DOEE conducts survey on the ground and their data is more accurate) and presented the strong comeback after a decade of absence. The %Score for SAV increased to 100 from zero 4 years ago! These gains pushed 2 sections of the river to a passing  and the entire Anacostia River received the D grade for the first time since AWS started to assess the river!

2018 STOR 2016Data

Eastern Floater Pyganodon cataracta 2

Building on previous years' discovery of the rebounding mussel population in the river, we conducted a river-wide mussel survey. We partnered with the Maryland Department of Natural Resources (MDDNR) and released the report in February 2016. We have also been doing our own mussel surveys since then. To date, AWS and MDDNR have identified eight species of freshwater mussels in the river (Eastern floater, Eastern elliptio, Paper pondshell, Eastern pondmussel, Tidewater mucket, Atlantic spike, and Eastern Lampmussel and Alewife floater) at Dueling Creek, the Bladensburg wetlands, Kingman Marsh, Kenilworth Marsh, the main stem of the river and Buzzard Point. Also, Robert Aguilar from Smithsonian Environmental Research Center found a special freshwater snail that likes good water quality at Buzzard Point of the Anacostia River.

These are eight of the nine species known to occur in the tidal Potomac River. Six of the eight species observed are listed as rare, vulnerable or critically imperiled in Maryland and/or the District making their conservation and restoration a priority in the Anacostia River. One adult mussel can filter more than 10 gallons of water a day, so a recovery of the mussel population is likely to be beneficial for the water quality of the river. The confluence of the river boasts a high abundance of mussels of seven of the eight species identified in the river, making that portion of the river a “seed source” for the propagation of these mussels in the rest of the river and an important area for mussel biofiltration.


In 2016 AWS captured a photo of what we suspect to be a river otter with our trail camera. And DOEE took photos of the Northern River Otter at the National Arboretum! 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.

Comparing Year to Year

2018 STOR 2016Data for 5 years

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. 

These effects appear to be at play here for dissolved oxygen (DO). Intense rain events during the grading period results in regular sewage and runoff discharges to the lower river from the District’s Combined Sewer Overflow (CSO) system (see Precipitation Impact for details). 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. 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 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.

Despite the various weather patterns, dry weather or wet, the trend of water clarity have 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 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!

The improvement in Chlorophyll a is another indicator that the water is becoming clearer because the better %Score of Chlorophyll a means the less amount of algae in the water and less greenish. Some of this may be a result of earlier improvements to the CSO system that have reduced the number of smaller and more frequent releases to the river, which is dirtier “first flush” runoff from the District, being diverted to the Blue Plains Plant for treatment. The reduction of nutrient inputs to the river from these system upgrades (60% improvement to date) may be an important factor in the improvement of Chlorophyll a and water clarity. Again, the improving trend is not clearly visible in the table. However, again, when we examine trend, 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.

2018 SOTR Toxics TrashScoring finalv2

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 while river portions continue to be studied. However, due to the high expectation that Record of Decision on the toxic sediment may happen sometime soon, the score for “plan to remove toxics” has improved significantly.  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, this score/grade will remain low.

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 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 change. Our food packing lifestyle could be changed so that food wrappers (chip bags, etc.) will not be discarded.  In 2017 AWS recognized significant effort that Prince George’s County started to reduce the amount of trash.  This boosted the score in “Solid plan to remove trash in MS4,” “Funding,” and “Implementation.”  However, several laws introduced in Maryland to reduce trash seem NOT working.  This downgraded the score for “Regulation for behavior change.”

Data Analysis

Dissolved Oxygen

EcoCheckAssessment DO

The amount of dissolved oxygen (DO) has been steadily improving in all three sections of the river except in very recent years. The sharp drop in 2013 seems to be because of weather patterns (See Precipitation Impact for more information) that was not favorable to DO. There were many intense rainfall events that regularly caused Combined Sewer Overflow events in downstream DC in both 2013 and 2014. 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.

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.

However, 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 tend to become low.  This seemed to have happened in 2016.  The upstream portions of the tidal river (MD Anacostia and Upper DC Anacostia) had relatively low DO values in 2016.  The most downstream portion of the river (Lower DC Anacostia) is influenced by oxygen-rich Potomac River water and tend to have higher DO values.

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).

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 Anacostia River will see benefits from the project starting in 2018. The current schedule has the Blue Plains and Anacostia River Tunnels in service in March 2018, at which time the combined sewer overflows to the Anacostia River will be reduced by 81 percent. Further, the project will reduce combined sewer overflows by 98 percent at completion in 2022. Both DC sections will then see significant improvement in DO levels. However, by improving existing infrastructure and maintaining it better, DC Water already reduced 40% of CSO by 2009 and 60% of it by 2011.

Fecal Bacteria

EcoCheckAssessment FecalBacteria

Many Anacostia watershed residents know of the Combined Sewer Overflow problems in DC. The sewer system in DC is 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 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 2016 all sections improved from previous year.  On average the score for the entire Anacostia improved (from 56 to 63).  The %Score for Fecal Bacteria is on track for improvement. However, the improvement in the Maryland portion of the river (MD Anacostia) is due to the very dry weather in 2016 (data year). We need to see if MD Anacostia is really improving or not.

Water Clarity (Secchi Disk Depth)

EcoCheckAssessment Secchi

Water clarity indicator (Secchi Disk Depth) has been low for all sections in all years for which data is available.  However in 2016, Lower DC Anacostia had highest %Score of 59% while the scores have been almost always below 50 percent in the past. 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.

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, there seems to be improvement in the past several years in all sections. 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 resolving this grave issue, 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 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.


EcoCheckAssessment ChlorophyllA

%Scores for Chlorophyll a are improving. However, 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.

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

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.

Submerged Aquatic Vegetation (SAV)

EcoCheckAssessment Secchi 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 survey on the ground and the data is more accurate.

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 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%. 

Stormwater Runoff Volume

Northwest Branch

 Score NWBranch

Northeast Branch

 Score NEBranch

Precipitation Impact

Intense Rainfall Analysis

The %Score of dissolved oxygen (DO) for the entire Anacostia in 2016 (data year for 2018 Report Card) decreased from 54 to 48. There are many factors that influence on water quality as discussed below. Thus, the relationship between the precipitation pattern and %Score of DO is quite complex.  Also, AWS found that discussing only intense rainfall events may not be appropriate to explain the %Score of DO because rainfall events actually brings oxygen rich water to the river.  Raindrops are exposed to air.  Thus, rainwater is rich in DO.  Moderate precipitation that will not cause Combined Sewer Overflow will bring large amount of dissolved oxygen to the river improving %Score of DO.  From the point of view, AWS added Daily Precipitation Analysis section on this page next to this section.

Because the District has a Combined Sewer Overflow (CSO) system that carries raw sewage and rainwater in the same pipe, the mixture will be discharged when it rains approximately more than 0.5 inches. After an intense rainfall, AWS has observed from monitoring that DO values become very low for approximately 2 weeks. An example graph is inserted below.

DO detail

Therefore, we counted number of days that had intense precipitation in the previous 14 days for each year and compared the number with the given year’s %Score.  That number is listed as "Intense Rain Days" in the table below.

Intense Rain Days 104 48 55 58 93 103 60 42
%Score of DO 72 70 68 48 41 58 54 48

The Anacostia Watershed experienced frequent intense rainfall events in 2009, 2013, and 2014, from April through October, when we did our assessment. However, we had high %Score in 2009. Also we had low %Scores when we had less intense rainfall events in 2012, 2015, and 2016. This indicates that intense rainfall events are not causitive to %Score of DO.

Comparing 2009 to 2014 we see 1 day difference in the amount of intense rain days, but the DO scores are vastly different. This is probably because the intensity of rainfall was stronger in 2014 than in 2009 though the frequency was similar. Also, the tide might have influenced DO values. If there is an intense rainfall when the tide is coming in, the CSO discharge will be carried to upstream portion of the Anacostia, thus, the negative influence will remain longer.

In 2016, there weren’t so many intense rainfall events. 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 the oxygen supply during very dry weather, the amount of oxygen tends to become low.  This seemed to happen in 2016.

Daily Precipitation Analysis

Since the intense rainfall analysis does not explain the %Scores of DO very well, AWS started Daily Precipitation Analysis in the 2017 State of the River Report (data year is 2015). We have counted number of days over various amount of precipitation. The result is summarized in the table and graph below.

%Score of DO and Number of Days over Various Precipitation*

# of days over >0.5 inches 25 13 18 14 16 14 21 12
# of days over >0.6 inches 17 12 15 8 13 14 17 10
# of days over >0.7 inches 16 7 14 7 13 13 13 7
# of days over >0.8 inches 13 6 12 7 12 10 10 6
# of days over >0.9 inches 10 6 9 6 10 9 8 4
# of days over >1.0 inches 9 5 8 5 10 8 6 3
%Score of DO 72 70 68 48 41 58 54 48

Number of days above various levels of daily precip

The above graph can explain the %Score better than the discussion in Intense Rainfall Analysis. Our hypothesis is that when the watershed has a smaller amount of precipitation events (blue thin line, # of days over >0.5 inches), the %Score is higher and when we have higher number of intense rainfall events (orange line, # of days over >1.0 inches), the %Score is generally lower and worse.  However, after analysing the 2016 daily precipitation data, it seems that frequent moderate-intense precipitation events may bring more benefits (higher DO values) than harm in terms of Dissolved Oxygen.

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.

runoff chart

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 ranges 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.

2018 SOTR Toxics TrashScoring finalv2


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:

  • Jim Foster, AWS President
  • Masaya Maeda, Water Quality Specialist
  • Maureen Farrington, Marketing Manager
  • Emily Conrad, Director of Development
  • Ariel Trahan, Director of River Restoration Programs
  • Matthew Gallagher, Manager of Community-Based Restoration
  • Mike Bento, Communications Consultant, Engage Strategies
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