U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1259

The Distribution of Submersed Aquatic Vegetation 

and Water Lettuce in the Fresh and Oligohaline 

Tidal Potomac River, 2007
Cover: During autumn 2007, in the Mattawoman Creek and other locations in the Potomac River, single plants and clusters of water 

lettuce were discovered growing over the top of submersed aquatic vegetation beds. (Photograph by Nancy Rybicki.)
The Distribution of Submersed Aquatic Vegetation 

and Water Lettuce in the Fresh and Oligohaline 

Tidal Potomac River, 2007

By Sarah Hunter Campbell, Nancy B. Rybicki, and Edward R. Schenk

Open-File Report 2014–1259

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Campbell, S.H., Rybicki, N.B., and Schenk, E.R., 2015, The distribution of submersed aquatic vegetation and water 

lettuce in the fresh and oligohaline tidal Potomac River, 2007: U.S. Geological Survey Open-File Report 2014–1259, 

33 p., http://dx.doi.org/10.3133/ofr20141259.

ISSN 2331-1258 (online)
iii

Acknowledgments

This work could not have been completed without the help of volunteers who, alongside U.S. Geological 

survey staff, worked long hours on the boat to gather data: Patti Marcoe, Barbara Bartow, and Paul Roche. 

We are also grateful to Curtis Dalpra, from the Interstate Commission on the Potomac River Basin, who 

identified water lettuce in the Potomac while volunteering his assistance with the shoreline survey on 

October 6, 2007. Support for this study is gratefully acknowledged from the U.S. Army Corps of Engineers, 

Baltimore, Maryland; the Metropolitan Washington Council of Government’s Aquatic Plant Management 

Program; and the Fisheries Division of the District of Columbia Department of Health.

U.S. Geological Survey programs providing support for this study were the National Research Program and 

Chesapeake Bay Program.
iv

Contents

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Methods...........................................................................................................................................................2

Results .............................................................................................................................................................3

Upper Tidal Potomac River..................................................................................................................3

Lower Tidal Potomac River..................................................................................................................4

Upper Oligohaline Potomac River Estuary .......................................................................................5

References Cited............................................................................................................................................6

Figures

1. Study area showing the three river segments of the Potomac River and 

the locations of the Aquatic Plant Management Program harvest sites in 

the tidal Potomac River................................................................................................................8

2. Percent cover of hydrilla in submersed aquatic vegetation beds located in 

the tidal Potomac River from Washington, D.C., to Dogue Creek, Va., 2007 .......................9

3. Percent cover of hydrilla in submersed aquatic vegetation beds located in 

the tidal Potomac River from Dogue Creek, Va., to Quantico Creek, Va., 2007.................10

4. Percent cover of hydrilla in submersed aquatic vegetation beds located in 

the tidal Potomac River from Chopawamsic Creek, Va., to the end of the river 

segment, 2007..............................................................................................................................11

5. Location of each field bed in a continuous shoreline survey of 

Washington, D.C., 2007...............................................................................................................12

6. Location of each field bed in a continuous shoreline survey from 

Washington, D.C., to Broad Creek, Md., 2007.........................................................................13

7. Location of each field bed in a continuous shoreline survey from Swan 

Creek, Md., to Gunston Cove, Va., 2007...................................................................................14

8. Location of each field bed in a continuous shoreline survey from Mason 

Neck, Va., to Quantico Creek, Va., 2007 ..................................................................................15

9. Location of each field bed in a continuous shoreline survey near Quantico, Va., 

and Mallows Bay, Md., 2007 .....................................................................................................16

10. Location of each field bed in a continuous shoreline survey from Wades Bay, 

Md., to Potomac Creek, Va., 2007.............................................................................................17

11. Location of each field bed in a continuous shoreline survey from Aquia Creek, 

Va., to the end of the river segment, 2007...............................................................................18

12. Distribution of water lettuce in the tidal Potomac River between Mason Neck 

and Aquia Creek, Va., 2007 ........................................................................................................19

13. Distribution and density of submersed aquatic vegetation and the locations of the 

aquatic plant management harvest sites in the tidal Potomac River from Washington, 

D.C., to Broad Creek, Md., 2007 ................................................................................................20

14. Distribution and density of submersed aquatic vegetation and the locations 

of the aquatic plant management harvest sites in the tidal Potomac River from 

Chopawamsic Creek, Va., to the downstream extent of the study, 2007...........................21
v

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

meter (m) 1.094 yard (yd) 

Area

square kilometer (km2) 247.1 acre

square meter (m2) 10.76 square foot (ft2) 

square kilometer (km2) 0.3861 square mile (mi2)

15. Distribution and density of submersed aquatic vegetation and the locations 

of the aquatic plant management harvest sites in the tidal Potomac River 

from Broad Creek, Md., to Chopawamsic Creek, Va., 2007..................................................22

16. Percent of available habitat that was vegetated in each river segment from 

1985 to 2007..................................................................................................................................23

17. Area occupied by submersed aquatic vegetation for each river segment from 

1985 to 2007..................................................................................................................................23

Table

1. Percent canopy cover of each species and Shannon diversity index for field 

beds in the tidal Potomac River, 2007......................................................................................24
vi
Abstract 

Surveys documenting the composition of species of submersed aquatic vegetation (SAV) have been conducted in the 

Potomac River for decades. These surveys can help managers assess the proportion of native and exotic plants in the river or 

can be used to determine relationships between native and exotic plants, environmental conditions, and wildlife. SAV coverage 

increased from 2005 to 2007 throughout the fresh and oligohaline study area. The 2007 survey documented here determined 

that eleven species of SAV were present. The abundance of the exotic species Hydrilla verticillata (hydrilla) was relatively low, 

and species diversity was relatively high compared to previous years. The survey also revealed a new population of the invasive, floating aquatic plant Pistia stratiotes (water lettuce). In 2007, water lettuce, the latest exotic aquatic plant to be found in 

the fresh to oligohaline portion of the Potomac River, was most abundant in Mattawoman Creek, Charles County, Maryland. 

However, it was not observed in the fresh to oligohaline portion of the Potomac River in the summer of 2008. An understanding 

of the distribution of SAV species and factors governing the abundance of native and invasive aquatic species is enhanced by 

long-term surveys.

Introduction 

Submersed aquatic vegetation (SAV) is a critical component of the Potomac River ecosystem (fig. 1). Although SAV 

provides important habitat for fauna and stabilizes bottom sediment, very dense beds may restrict recreational and commercial 

navigation. Exotic species of SAV were managed by the Metropolitan Washington Council of Governments from 1986 to 2007 

as part of the Potomac Aquatic Plant Management Program (PAPMP). Selected beds of primarily exotic SAV species that limit 

navigation were harvested mechanically. The program began in 1986 when approximately 40 acres of plants were harvested 

from 18 sites (fig.1; Metropolitan Washington Council of Governments, 1987).

Monitoring efforts are an effective means of quantifying the distribution and abundance of the four exotic species in the 

river ecosystem—Hydrilla verticillata (hydrilla), Najas minor (naiad), Potamogeton crispus (curly pondweed), and Myriophyllum spicatum (milfoil)—and nine other native SAV species. In 2007, the U.S. Geological Survey (USGS) monitoring efforts led 

to the discovery of a substantial population of Pistia stratiotes (water lettuce), an exotic subtropical species of floating aquatic 

vegetation (Langeland and Burks, 1998). This was the first documented siting of this species in the Potomac River.

Annual surveys of SAV beds provide a basis for identifying large-scale changes and trends throughout the ecosystem and 

allow managers to evaluate the effectiveness of resource management policies directed toward improving water quality (Rybicki 

and Landwehr, 2007) and managing invasive plants (Hershner and Havens, 2008). The USGS has monitored the distribution and 

composition of SAV beds in the fresh and oligohaline (salinity 0.5 to 5) tidal Potomac River from 1978 to 2007 by using transect 

sampling (1978 to 1981, 1985 to 1987, 2002, and 2006) and shoreline surveys (1983 to 2005 and 2007; Rybicki and Landwehr, 

2007, Ruhl and Rybicki, 2010). No shoreline survey was conducted in 2006; instead, 15 transects were sampled in the tidal fresh 

and oligohaline Potomac River between Piscataway and Pomonkey Creeks on both Maryland and Virginia shores on May 8 and 

October 18. Since 1998, the government of the District of Columbia has conducted surveys and provided the data to the USGS 

for the Washington, D.C. portion of the Potomac and Anacostia Rivers (Rottman, 1999; Ryan, 2005, 2006, 2007, 2008).

A list of species of SAV observed in beds in the tidal Potomac River is incorporated into the Virginia Institute of Marine 

Science (VIMS) annual report on SAV distribution in the Chesapeake Bay. The VIMS report and methods are available at http://

www.vims.edu/bio/sav (Orth and others, 2008). Additional publications concerning SAV distribution in the Potomac River can be 

found at http://water.usgs.gov/nrp/proj.bib/sav/wethome.htm.

The Distribution of Submersed Aquatic Vegetation and 

Water Lettuce in the Fresh and Oligohaline Tidal Potomac 

River, 2007

By Sarah Hunter Campbell,1 Nancy B. Rybicki,2 and Edward R. Schenk2

1

Aarcher, Inc.

2

U.S. Geological Survey.
2 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

Methods

During the 2007 survey, the study area in the Potomac River was divided into three reaches: (1) upper tidal river (UTR), (2) 

lower tidal river (LTR), and (3) upper oligohaline estuary (UOE) (fig. 1). Observations of species composition in SAV beds were 

done by boat at approximately low tide (±2 hours) to optimize SAV visibility from the water surface. Surveys were conducted 

from August to October 2007. Researchers identified submersed plants to species level, recorded the species composition of 

each bed, and estimated the percent cover for each species within the bed. As in previous years, the USGS monitored areas 

downriver from the Woodrow Wilson Bridge (Interstate 95), whereas colleagues at the District of Columbia District Department 

of the Environment (DDOE) examined Washington, D.C. waters in the tidal Anacostia and Potomac Rivers (Rottman 1999; 

Ryan 2008). 

The monitoring effort in 2007 consisted of a continuous survey of all shoals and SAV beds within the study area (fig. 1). 

SAV field beds are the isolated or contiguous SAV beds of different species composition sampled by boat. USGS personnel 

outlined SAV beds on 1:24,000-scale USGS quadrangle maps, indicating the location of all observations including unvegetated 

shoals (see Ruhl and others, 1999). DDOE personnel used a global positioning system (GPS) to delineate the perimeter or length 

of beds and to record locations of each field bed. The SAV beds documented by the USGS and DDOE were then entered into a 

geographic information system (GIS) to create maps of distribution and abundance. The observation date, percent of each species, Shannon diversity index, and bed density for each field bed are listed in table 1. The Shannon diversity index for each field 

bed is calculated as:

M

v=1

Diversity –1 ((Pv /100) ln(Pv /100)) =× × ∑ 

 (1)

where 

 M represents richness (the total number of species observed), 

 Pv represents the proportional coverage (from 0 to 100 percent) of each species, and

 v represents each species from 1 to M. 

Diversity in each bed can range from 0.00 (if one species is present) to 2.49 (if all 12 species commonly found in the Potomac 

are present in equal percentages). The percent cover data for each species shown in table 1 corresponds to field bed locations 

shown in figures 2 to 12. Observations of the percent cover of colonies of water lettuce on top of SAV beds or the observation of 

a single cluster of plants floating in the channel were made from October 6 to October 18. 

SAV beds shown in figures 13, 14, and 15 were delineated by VIMS (http://www.vims.edu/bio/sav/) on the basis of aerial 

photographs acquired from August to October, then digitized and classified for ground cover density (from estimates of percent 

cover). The area and density of each photo-interpreted (PI) bed was determined by VIMS. Density was determined using the 

Crown Density Scale adapted from Paine (1981). Bed densities range from 1 to 4, with a density of 1 corresponding to less than 

10 percent vegetation coverage, a density of 2 representing from 10 to 40 percent coverage, a density of 3 representing from 41 

to 70 percent coverage, and a density of 4 corresponding to 71 to 100 percent coverage. The VIMS delineation process resulted 

in bed area outlines to which corresponding field data on species composition were added. Some SAV beds were visible with 

aerial photography but were not observed in the field if the area was not navigable due to water depth or obstacles. The VIMS 

SAV coverage data did not include beds below their detection limit. Therefore, beds shown in figures 2 to 4 do not correspond 

exactly with VIMS beds. 

The percent cover for each species in the three river segments (UTR, LTR, UOE) is summarized in the results section. The 

area of each species within a VIMS PI bed is computed on the basis of a weighted-average formula. Using GIS software, each 

of the field beds was aligned with the PI beds to determine the area of each field bed and subsequently to calculate the coverage 

by species in each PI bed where species data were available. If more than one field observation was made in a PI bed, the PI bed 

area was subdivided according to the relative size of each field bed and averaged species data proportionally (weighted average) 

to determine the percentage of each species in a PI bed and in the cumulative area of the study in each river reach (Rybicki and 

Landwehr, 2007). 

Aquatic plant managers also need to know if species composition fluctuated from dominance of one species to another or 

if SAV coverage persisted at a location between years. Therefore, comparisons of spatial coverage of SAV and dominant species 

(coverage ≥40 percent) between 2007 (this study) and 2005 (Rybicki and others, 2008) or previous years (Ruhl and others, 1999; 

Ruhl and Rybicki, 2010; http://www.vims.edu/bio/sav/) are described for each river segment. The description of temporal spatial 

patterns in exotic species coverage enhances management efforts to understand interannual variation in SAV and predict the 

need for harvesting exotic species the following year.
Results 3

Results

The shoreline survey included 274 observations of field beds of various sizes (72 m2 to 313 km2) and densities (table 1). 

Many of the PAPMP harvest sites in the UTR, LTR, and UOE had 70 to 100 percent cover (figs. 13 to 15). Of the 11 species 

observed in the Potomac River in 2007, four were exotic (hydrilla, milfoil, naiad, and curly pondweed). Hydrilla did not dominate (coverage ≥40 percent) in any river segment in 2007, whereas from 1985 to 2005, hydrilla was frequently the dominant 

species in most river segments (Rybicki and Landwehr, 2007; Ruhl and Rybicki, 2010; Rybicki and others, 2008). Hydrilla 

and Ceratophyllum demersum (coontail) were the most abundant species in the UTR; milfoil was the most abundant species in 

the LTR and the UOE. Naiad coverage was similar to previous years, comprising 5 to 15 percent of SAV coverage in the river 

segments. Vallisneria americana (wild celery) SAV coverage was low in 2007, comprising 1 to 10 percent of SAV coverage 

in the river segments. As in 2005, Elodea spp. (waterweed) was not present in 2007, but Stuckenia pectinata (sago pondweed) 

and curly pondweed were observed in trace amounts. Some species were relatively rare, namely the macroalga Chara vulgaris

(muskgrass), Potamogeton pusilus (slender pondweed), and Potamogeton perfoliatus (redhead grass). Najas guadalupensis

(southern naiad) and Heteranthera dubia (water stargrass) were rare in 2005, but increased substantially in 2007.

Water lettuce was observed in approximately 161 hectares in the LTR and UOE in 2007. The floating aquatic vegetation 

was found in the river in various locations between Mason Neck and Aquia Creek (fig. 12). These discoveries led to an organized effort to monitor for water lettuce in 2008. The Freshwater Submerged Aquatic Vegetation Partnership, a group of Federal, 

State and university staff focused on aquatic plants, convened a group to determine if the water lettuce, a subtropical plant, 

could overwinter and survive in the Potomac River the following year. The Partnership members made observations from boats 

throughout the fresh to oligohaline portion of the Potomac River in the summer of 2008. They found no water lettuce in the 

study area in 2008. In addition, signage was placed at boat ramps in Maryland to educate the public not to release exotic aquatic 

species into the waterways and to report observations of water lettuce to Maryland Department of Natural Resources. 

The percent of available habitat (area less than 2 m deep) that was vegetated varied over time in the UTR, LTR, and UOE 

but was at a maximum in 2007 in all river segments (fig. 16). However, no river segment has had vegetation in more than 

60 percent of the available habitat from 1985 to 2007. SAV coverage increased from 2005 to 2007 throughout the fresh and 

oligohaline study area (fig. 17). 

Upper Tidal Potomac River

In the upper tidal river (UTR), the following eight SAV species were found in 2007, in order from most to least abundant: 

hydrilla (28 percent), coontail (28 percent), milfoil (16.5 percent), naiad (15 percent), water stargrass (7.5 percent), and southern 

naiad, wild celery, or curly pondweed (less than 5 percent). Compared to 2005, coontail, naiad, southern naiad, and water stargrass coverage increased in 2007, while hydrilla and wild celery coverage decreased and milfoil coverage remained the same. 

Muskgrass was not observed in 2007, although it has been found in this segment of the river in trace amounts for the past few 

years. Curly pondweed was observed in this segment of the study area for the first time in several years. The number of species 

observed in the UTR decreased from nine in 2005 to eight in 2007. 

No SAV was observed in the Washington, D.C. portion of the tidal Anacostia River (fig. 5), yet a few beds were 

present there in the past. A perennial bed that has persisted for many years in the Washington Channel, at the confluence of 

the Anacostia River and Potomac River, was not observed in 2007.

In Washington, D.C., SAV coverage in 2007 (figs. 2, 5, 13, and 16) increased substantially from 2005. Coverage was higher 

in 2007 than it had been for several years. SAV coverage in Washington, D.C. waters declined dramatically after 2003 when 

precipitation and river flow (USGS gage station 01646500, http://waterdata.usgs.gov/nwis/sw) were well above average. The 

high sediment load and high flows may have buried SAV or scoured it away, or the cloudy conditions and muddy waters reduced 

available light reaching the bottom and diminished SAV productivity. SAV was abundant from the Chain Bridge to Roosevelt 

Island in 2007 (figs. 2, 5, and 13; table 1) for the first time since 2002 (http://www.vims.edu/bio/sav). The beds north of Roosevelt Island to the Chain Bridge were dominated by water stargrass, although hydrilla and naiad were also found in many of the 

beds in 2007 (fig. 5; table 1). These beds were relatively small. The beds around Roosevelt Island were dominated by hydrilla, 

although water stargrass was present in many beds. Small populations of wild celery and naiad were also observed. 

SAV coverage along the Washington, D.C. shoreline of the Potomac River south of Roosevelt Island in 2007 (figs. 2, 5, and 

13; table 1) increased substantially from 2005. Wild celery dominated most of these beds, although water stargrass and hydrilla 

were also observed. SAV beds along the Virginia shoreline of the Potomac River south of Roosevelt Island also expanded since 

2005. In contrast, a large bed that was present near a creek at Reagan National Airport in 2005 was not observed in 2007. These 

beds along the Virginia shoreline alternated in dominance between hydrilla and water stargrass; however, naiad and coontail 

were also observed there in 2007. 
4 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

In 2007, vegetation along the Virginia side of the Potomac River from National Airport to the Woodrow Wilson Bridge was 

intermittent and diverse; the beds contained water stargrass, coontail, hydrilla, naiad, and milfoil (figs. 2, 6, and 13; table 1), 

where, in 2005, the beds consisted mostly of hydrilla and some naiad. Large, dense beds were present in the middle of the 

Potomac River, just upstream from the Woodrow Wilson Bridge (figs. 6 and 13). These beds were also diverse, containing 

hydrilla, coontail, milfoil, naiad, water stargrass, and southern naiad. The SAV bed last observed in 2002 in the middle of the 

Potomac River just south of the Woodrow Wilson Bridge returned in 2007 and was dominated by hydrilla (figs. 2, 3, and 13). 

SAV beds along the Maryland shore in the UTR in 2007 were dominated by hydrilla or coontail with milfoil, naiad, and 

water stargrass mixed in (figs. 2 and 6; table 1). Beds just north of Broad Creek were dominated by coontail, although hydrilla 

was abundant and water stargrass, naiad, and wild celery were also observed. Broad Creek was dominated by coontail, as were 

the beds located along the shore south of Broad Creek to Swan Creek. SAV beds in Swan Creek were dominated by coontail 

in 2007 (fig. 7), but were dominated by hydrilla in 2005. Hydrilla dominated the SAV beds along the Maryland shore south of 

Swan Creek to Piscataway Creek in 2007 (figs. 2 and 7). On the upstream shore of Piscataway Creek, beds were dominated by 

hydrilla while beds in the middle of the creek had less than 40 percent hydrilla, and also contained coontail, water stargrass, and 

naiad. The beds on the downstream shore of Piscataway Creek were often dominated by coontail, as were those located along 

the Maryland shore throughout the lower extent of the UTR. However, beds were occasionally dominated by hydrilla and contained a mixture of other SAV in 2007. 

SAV coverage was continuous along the Virginia shore between Hunting Creek and Little Hunting Creek in 2007 (fig. 2); 

however, SAV beds were not observed in the upper half of that Virginia shore in 2005. The new beds were dominated by 

hydrilla, although coontail and naiad were abundant and wild celery, water stargrass, southern naiad, and milfoil were also 

observed in 2007 (figs. 2, 6, and 7; table 1). The number of species observed in the beds along the Virginia shore increased substantially from 2005 to 2007. In 2005, hydrilla and milfoil altered in dominance along the Virginia shore south to Little Hunting 

Creek and coontail was abundant. In 2007, hydrilla dominated a couple of beds, but coontail, naiad, southern naiad, and milfoil were abundant and water stargrass and wild celery were also observed. Hydrilla dominated the beds at the mouth of Little 

Hunting Creek, but those were also well mixed with other common species of SAV. Fairly large beds were observed in 2007 in 

the channel of the Potomac River in front of Little Hunting Creek that extended south of the creek to the midway point between 

Little Hunting Creek and Dogue Creek. These beds in the channel were dominated by coontail, although near the southern end 

of the channel beds there was a bed dominated by milfoil. Hydrilla, naiad, and southern naiad were also observed in these beds. 

The SAV beds along the Virginia shore south of Little Hunting Creek to the lower extent of the UTR were dominated by milfoil, 

well mixed with coontail, hydrilla, and to a lesser extent, naiad and southern naiad. In 2005, the lower extent of the UTR on 

the Virginia shore was dominated by wild celery, but in 2007 very little was observed. Milfoil, coontail, and hydrilla altered in 

dominance in Dogue Creek, but southern naiad and naiad were also observed in 2007.

The shore just upstream from Little Hunting Creek supported the only traces of muskgrass in the entire study area in 

2005, while in 2007, muskgrass was not observed at all in the UTR (fig. 7; table 1). Trace amounts of sago pondweed were 

also observed in the UTR in 2005, but sago pondweed was not observed in 2007. A small population of curly pondweed was 

observed in 2007; it had not been observed in Dogue Creek since 1999. 

Lower Tidal Potomac River

In the lower tidal river (LTR) in 2007, 11 SAV species were found. The SAV coverage was, from most to least abundant, 

milfoil (32 percent), hydrilla (26 percent), coontail (20 percent), naiad (9 percent), wild celery (8 percent), and southern naiad, 

water stargrass, muskgrass, curly pondweed, slender pondweed, and redhead grass (less than 5 percent). SAV coverage increased 

from 2005 to 2007 for most species, with milfoil exhibiting the greatest increase. Milfoil was the most abundant species of the 

LTR in 2007, whereas hydrilla was the dominant species in 2005. Hydrilla and wild celery coverage dropped by almost half, 

while coontail coverage remained the same from 2005 to 2007. Four species were new to this segment of the study area since 

2005, and all were in trace amounts in 2007: muskgrass, curly pondweed, slender pondweed, and redhead grass. The number of 

species in this segment of the study area increased from 7 to 11 species from 2005 to 2007.

Hydrilla was the dominant species in the beds on the upstream shore of Gunston Cove, similar to 2005. Milfoil dominated 

the SAV beds along the downstream shore of Gunston Cove and dominated a small bed in the middle of the mouth of the cove 

in 2007 (figs. 3 and 7; table 1). SAV beds in the back of Gunston Cove alternated in dominance between milfoil, southern naiad, 

coontail, and hydrilla, where hydrilla dominated most of these beds in 2005. A small population of water stargrass was also 

observed in these beds in 2007, where it was not present in 2005. In the narrow fringing downstream beds of Gunston Cove, 

naiad, wild celery, and hydrilla were the most abundant species in 2007. Hydrilla was the most abundant species and dominated 

some beds in locations across from Gunston Cove and south of Pomonkey Creek, on the Maryland side of the Potomac River. 

However, water stargrass, coontail, and milfoil were also abundant species with a smaller presence of naiad, southern naiad, and 

wild celery in 2007.
Results 5

Hydrilla was the dominant species in the beds on the upstream shore of Gunston Cove, similar to 2005. Milfoil dominated 

the SAV beds along the downstream shore of Gunston Cove and dominated a small bed in the middle of the mouth of the cove 

in 2007 (figs. 3 and 7; table 1). SAV beds in the back of Gunston Cove alternated in dominance between milfoil, southern naiad, 

coontail, and hydrilla, where hydrilla dominated most of these beds in 2005. A small population of water stargrass was also 

observed in these beds in 2007, where it was not present in 2005. In the narrow fringing downstream beds of Gunston Cove, 

naiad, wild celery, and hydrilla were the most abundant species in 2007. Hydrilla was the most abundant species and dominated 

some beds in locations across from Gunston Cove and south of Pomonkey Creek, on the Maryland side of the Potomac River. 

However, water stargrass, coontail, and milfoil were also abundant species with a smaller presence of naiad, southern naiad, and 

wild celery in 2007.

Wild celery was the dominant species around Mason Neck (Virginia) in 2007, as also was observed in 2005. Milfoil was 

the dominant species at the mouth of Pomonkey Creek in 2007 (figs. 7 and 8), where hydrilla dominated in 2005. However, the 

beds at the mouth and in Pomonkey Creek were well mixed with coontail, water stargrass, hydrilla, and small populations of 

southern naiad, naiad, and wild celery in 2007 (figs. 3 and 8; table 1). SAV was sparse at Indian Head between Pomonkey Creek 

and downstream to Mattawoman Creek and consisted mainly of beds that altered in dominance between water stargrass, milfoil, 

hydrilla, and naiad. Small populations of coontail and southern naiad were also observed along this portion of the Maryland 

shore in 2007 (fig. 8; table 1).

SAV coverage in the Mattawoman Creek increased substantially from 2005. Coontail, milfoil, and hydrilla were abundant 

in the mouth of the Mattawoman in 2007 (figs. 3, 8, and 14; table 1). Wild celery was one of the dominant species in 2005, 

but in 2007 only a few small populations were observed at the mouth and in the middle of the creek. There was a substantial 

increase in milfoil coverage through much of the Mattawoman, where it dominated several beds throughout the creek. Hydrilla 

was dominant in the upstream portions of the Mattawoman Creek, but occasionally there were beds dominated by coontail. 

Naiad decreased while southern naid increased from 2005 to 2007 (fig. 8; table 1). Southern naiad was only found in trace 

amounts in 2005.

SAV coverage decreased in Chicamuxen Creek from 2005 to 2007. Coontail and milfoil were again the most abundant 

species and smaller populations of hydrilla, wild celery, naiad, and water stargrass were observed in 2007 (figs. 3, 8, 9, and 14; 

table 1). Chicamuxen Creek is traditionally one of the more diverse beds in the study area, although in 2007, the number of 

species decreased as a result of the lack of southern naiad.

SAV coverage in Belmont Bay increased substantially from 2005 to 2007. In 2005, hydrilla, southern naiad, and wild 

celery were found in the three beds observed. In addition to those species observed in 2005, in 2007 milfoil and trace amounts 

of slender pondweed and redhead grass were found (figs. 3, 8, and 14; table 1). New beds were observed along the shore on the 

upstream side of the mouth of Belmont Bay, where milfoil, coontail, hydrilla, and wild celery were abundant and supported the 

only population of muskgrass found in the entire study area. Hydrilla and southern naiad alternately dominated beds along the 

upstream shore of Belmont Bay; these beds also supported the only populations of slender pondweed and redhead grass in the 

study area. In the remainder of Belmont Bay and at the mouth of the Occoquan River, hydrilla, milfoil, and wild celery altered in 

dominance. 

Neabsco Creek was dominated by hydrilla in 2007 (fig. 3), as it was in 2005. SAV coverage and diversity in Powells Creek 

and along the Virginia shore south to Quantico Creek increased considerably in 2007 (figs. 9 and 14; table 1). The SAV beds 

in Powells Creek were well mixed with coontail, hydrilla, southern naiad, wild celery, and milfoil in 2007, where hydrilla was 

dominant in 2005. Beds just south of the mouth of Powells Creek along the shore were dominated by wild celery, but along the 

shore closer to Quantico Creek and into the creek, the beds were very diverse, with milfoil dominating one bed on the upstream 

shore of the mouth of Quantico Creek. In 2005, hydrilla and coontail altered in dominance in Quantico Creek, but in 2007, milfoil, coontail, wild celery, hydrilla, and southern naiad were very abundant throughout the creek (figs. 3, 8, and 9; table 1).

The floating aquatic vegetation, water lettuce, was first discovered October 6 in the Mattawoman Creek. Afterwards it 

was also found in various beds in Chicamuxen Creek, Powells Creek, and Quantico Creek in this segment of the study area in 

2007 (fig. 12). Water lettuce did not exceed 10 percent coverage of any bed shown in figure 12. It was always located with SAV 

except where it was floating free in the channel of the Potomac River near Mason Neck. 

Upper Oligohaline Potomac River Estuary

Eight SAV species were present in 2007 in the upper oligohaline estuary (UOE) with the following composition: milfoil 

(40 percent), hydrilla (17 percent), stargrass (13 percent), coontail (12 percent), wild celery (9.5 percent), naiad (5 percent), and 

southern naiad and curly pondweed (less than 5 percent each). From 2005 to 2007, the coverage of milfoil increased substantially while hydrilla coverage, which was the dominant species in 2005, decreased. Coontail coverage also decreased, but water 

stargrass, wild celery, naiad, and southern naiad coverage increased compared to previous years. Curly pondweed was observed 
6 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

for the first time in the UOE in 2007. In 2005, hydrilla was the dominant species in many locations along the Virginia side of 

the Potomac River and milfoil and wild celery were the dominant species along the Maryland side, but in 2007 the beds on both 

sides of the river were diverse. Rarely was any species ≥40 percent of the total cover. The number of species observed in the 

UOE increased from eight in 2005 to nine in 2007.

Milfoil and wild celery codominated the only bed in the upper extent of the UOE on the Maryland side of the Potomac 

River north of Mallows Bay in 2007 (figs. 8 and 15; table 1), where milfoil and hydrilla were abundant in 2005. SAV in Mallows 

Bay consisted of three beds, one dominated by hydrilla, one by milfoil, and one by coontail in 2007 (figs. 4 and 8). Water stargrass, naiad, and southern naiad were also observed in 2007, whereas in 2005, only hydrilla, naiad, and coontail were observed. 

SAV coverage decreased in the bay north of Wades Bay and in Wades Bay from 2005 to 2007. One long bed extended through 

these two bays and was dominated by milfoil, although some wild celery, coontail, and water stargrass were also observed in 

2007. Wild celery dominated Wades Bay in 2005 but milfoil was dominant in 2007 (fig. 10; table 1).

Water stargrass was the most abundant species in the cove south of Quantico, Va., and north of the Chopawamsic Creek in 

2007 (fig. 9; table 1). Water stargrass, milfoil, and coontail were abundant in the region south of Quantico and along the shoreline south of Chopawamsic Creek. Water stargrass was observed in trace amounts in this area in 2005, but in 2007 it was abundant or dominant in many of the beds on the Virginia shore from Chopawamsic Creek to Aquia Creek (figs. 9 and 10; table 1). 

In 2007, milfoil dominated many of the beds in Aquia Creek, although beds around the mouth of the creek were dominated 

by water stargrass (figs. 4 and 10; table 1). Hydrilla, coontail, wild celery, naiad, and southern naiad were also found in the 

creek in 2007. In 2005, many Aquia Creek beds were dominated by coontail and the upstream beds and the south shore of Aquia 

Creek were dominated by hydrilla. The southern shoreline at the mouth of Aquia Creek was dominated by milfoil in 2007. This 

was also true of the cove just below Aquia Creek, although one bed contained the only population of sago pondweed in the 

UOE. The beds located on the northern mouth of Aquia Creek and the upstream shore of Potomac Creek were codominated by 

southern naiad and hydrilla or were dominated by milfoil, with populations of coontail and water stargrass also observed in 2007 

(figs. 4, 10, and 11; table 1). Within Potomac Creek, hydrilla dominated the SAV beds although wild celery, coontail, southern 

naiad, and water stargrass were also observed. One bed on the downstream shore of Potomac Creek was dominated by wild 

celery in 2007. SAV was not found beyond Potomac Creek in the lower extent of the UOE. 

Water lettuce was observed in the cove below Quantico Creek, Wades Bay, and Aquia Creek in this segment of the study 

area (fig. 12). Similar to the LTR, water lettuce coverage never exceeded 10 percent of a SAV bed and was generally located 

with SAV in the UOE.

References Cited

Hershner, C., and Havens, K.J., 2008, Managing invasive aquatic plants in a changing system—Strategic consideration of ecosystem services: Conservation Biology, v. 22, no. 3, p. 544–550. 

Langeland, K.A., Burks, K.C., eds., 1998, Identification and biology of non-native plants in Florida’s natural areas: Gainesville, 

Fla., University of Florida, 165 p., http://www.fleppc.org/ID_book.htm.

Metropolitan Washington Council of Governments, 1987, Potomac: SAV news, no. 2, Summer 1987.

Orth, R.J., Wilcox, D.J., Whiting, J.R., Nagey, L.S., Owens, A.L., and Kenne, A.K., 2008, 2007 Distribution of submerged 

aquatic vegetation in the Chesapeake Bay and coastal bays: VIMS Special Scientific Report Number 151. Final report to U.S. 

EPA, Chesapeake Bay Program, Annapolis, Md., Grant No. CB973219-01-0, http://web.vims.edu/bio/sav/sav07/index.html.

Paine, D.P., 1981, Aerial photography and image interpretation for resource management: New York, John Wiley and Sons, 

571 p.

Rottman, A., 1999, Aquatic vegetation monitoring 1998; Submitted to U.S. Fish and Wildlife Service for the Fisheries and Wildlife Division of the Government of the District of Columbia: Report F-2-8-13.

Ruhl, H.A., Rybicki, N.B., Reel, J.T., and Carter, V., 1999, Distribution and abundance of submersed aquatic vegetation in the 

Tidal Potomac River and Upper Potomac Estuary, Maryland, Virginia, and the District of Columbia, 1993–1998: U.S. Geological Survey Open-File Report 99–233, http://pubs.er.usgs.gov/publication/ofr99233. 

Ruhl, H.A., and Rybicki, N.B., 2010, Long-term reductions in anthropogenic nutrients link to improvements in Chesapeake Bay 

habitat: Proceedings of the National Academy of Science, v. 107, no. 38, http://www.pnas.org/content/107/38/16566.full.pdf.
References Cited 7

Ryan, D., 2005, 2004 Submerged aquatic vegetation survey of the Potomac and Anacostia Rivers within the District of Columbia; Submitted to U.S. Fish and Wildlife Service for the Fisheries and Wildlife Division of the Government of the District of 

Columbia: Report F-2-R-19.

Ryan, D., 2006, 2005 Submerged aquatic vegetation survey of the Potomac and Anacostia Rivers within the District of Columbia; Submitted to U.S. Fish and Wildlife Service for the Fisheries and Wildlife Division of the Government of the District of 

Columbia: Report F-2-R-20.

Ryan, D., 2007, 2006 Submerged aquatic vegetation survey of the Potomac and Anacostia Rivers within the District of Columbia; Submitted to U.S. Fish and Wildlife Service for the Fisheries and Wildlife Division of the Government of the District of 

Columbia: Report F-2-R-21. 

Ryan, D., 2008, 2007 Submerged aquatic vegetation survey of the Potomac and Anacostia Rivers within the District of Columbia; Submitted to U.S. Fish and Wildlife Service for the Fisheries and Wildlife Division of the Government of the District of 

Columbia: Report F-2-R-22. 

Rybicki, N.B., and Landwehr, J.M., 2007, Long-term changes in abundance and diversity of macrophyte and waterfowl 

populations in an estuary with exotic macrophytes and improving water quality: Limnology and Oceanography, v. 52, no. 3, 

p. 1195–1207.

Rybicki, N.B., Yoon, S.N., Schenk, E.R., and Baldizar, J.B., 2007, The distribution of submersed aquatic vegetation in the fresh 

and oligohaline tidal Potomac River, 2004: U.S. Geological Survey Open-File Report 2007–1198, 27 p., http://pubs.usgs.gov/

of/2007/1198/.

Rybicki, N.B., Justiniano-Vélez, E., Schenk, E.R., and Hunter, S.E., 2008, The Distribution of submersed aquatic vegetation in 

the fresh and oligohaline tidal Potomac River, 2005: U.S. Geological Survey Open-File Report 2008–1218, 35 p., http://pubs.

usgs.gov/of/2008/12.
8 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

Figure 1. Study area showing the three river segments (UTR, upper tidal river, LTR, lower tidal river, and UOE, upper 

oligohaline estuary) of the Potomac River and the locations of the Aquatic Plant Management Program harvest sites in the tidal 

Potomac River.

15' 77° 45'

45'

30'

0 1 2 4 6 8 10 Miles

0 1 2 4 6 8 10 Kilometers

EXPLANATION

Harvest site

UTR

LTR

UOE

VIRGINIA

MARYLAND

DC DE

NJ

WV

WASHINGTON, DC

VIRGINIA

Mount Vernon

Maryland Point

Quantico

MARYLAND

Potomac River

Anacostia

River

Chesapeake Bay
Figures 9

Figure 2. Percent (%) cover of hydrilla in submersed aquatic vegetation beds located in the tidal Potomac River from 

Washington, D.C., to Dogue Creek, Va., 2007. UTR is the upper and LTR is the lower tidal river study segment.

EXPLANATION

Percent Hydrilla verticillata

0%

1%–39%

40%–100%

Chain

Bridge

Hunting Creek

Anacostia

River

UTR and upstream

extent of study

Roosevelt

Island

Dyke

Marsh

Reagan

National

Airport

Oxon Run

Woodrow Wilson Bridge

Potomac River

Broad Creek

Swan Creek

Piscataway Creek

Little Hunting

Creek

Dogue Creek

Kingman

Island

UTR

LTR

77°10' 77°5' 77° 76°55'

38°55'

38°50'

45'

38°40'

0 0.5 1 2 3 Miles

0 0.5 1 2 3 Kilometers

U.S. Geological Survey

District Department of Environment

WASHINGTON, DC
10 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

Figure 3. Percent (%) cover of hydrilla in submersed aquatic vegetation beds located in the tidal Potomac River from Dogue 

Creek, Va., to Quantico Creek, Va., 2007. UTR is the upper and LTR is the lower tidal river study segment.

EXPLANATION

Percent Hydrilla verticillata

0%

1%–39%

40%–100%

77°20' 15' 77°10' 77°5' 77°

45'

38°40'

38°35'

30'

0 0.5 1 2 3 Miles

0 0.5 1 2 3 Kilometers

Quantico

Quantico Creek

Powells Creek

Neabsco Creek

Occoquan River

Belmont

Bay

Occoquan

Bay

Mason Neck Pomonkey Creek

Gunston

Cove

Dogue Creek

Piscataway Creek

Broad Creek

Swan Creek

Little Hunting

Creek

VIRGINIA

MARYLAND

Potomac River

Chicamuxen Creek

Mattawoman Creek

LTR

UTR

UOE

LTR

Indian Head

U.S. Geological Survey
Figures 11

EXPLANATION

Percent Hydrilla verticillata

0%1%–39%40%–100%

-76°55' -77° -77°5' -77°10' -77°15' -77°20' -77°25'

38°30'38°25'38°20'

MarylandPoint

NanjemoyCreek

oP

tr

oT

ab

cc o River

Potomac Creek

Aquia Creek

UOE

UOE and downstreamextent of study

Rt. 301

Br di ge

VIRGINIA

MARYLAND

MallowsBay

WadesBay

Potomac

River

ChopawamsicCreek

U.S. Geological Survey

0 1 2 3 0.5 Miles0 1 2 3 0.5 Kilometers

Figure 4. Percent (%) cover of hydrilla in submersed aquatic vegetation beds located in the tidal Potomac River from Chopawamsic Creek, Va., to the end of the river segment, 2007. UOE is the upper oligohaline estuary study segment.
12 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac EXPLANATION Field bed and number Chain Bridge 266 247 250 254 249 267 272 252 248 265 268 270 255 257 251 269 264 253 259 271 258 256 260 263 262 261 -77° -77°5' 38°55' 38°50'

0 1 2 3 Miles 0.50 1 2 3 Kilometers 0.5

VIRGINIA

Potomac River

WASHINGTON, DC

Kingman

Island

WASHINGTON, DC line

UTR and upstream extent of study

Anacostia River

Roosevelt Island

ReaganNationalAirport

District Department of Environment

MARYLAND

Figure 5. Location of each field bed in a continuous shoreline survey of Washington, D.C., 2007. UTR is the upper tidal river study segment.
Figures 13

Figure 6. Location of each field bed in a continuous shoreline survey from Washington, D.C., to Broad Creek, Md., 2007.

EXPLANATION

Field bed and number

43

19

18

245

11

44

14

13

248

48

244

46

20

17

15

241

16

273

243

45

274

47

242

246

77°5' 77°

38°50'

45'

0 0.25 0.5 1 1.5 2 Miles

0 0.25 0.5 1 1.5 2 Kilometers

VIRGINIA

MARYLAND

Potomac River

Woodrow Wilson Bridge

Oxon Run

Broad Creek

Hunting Creek

WASHINGTON, DC line

U.S. Geological Survey

District Department of Environment
14 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac EXPLANATION Field bed and number 43 171 32

8

202

31

30

7 9

11

26

5

190

2

21

1

6

12

25

192

3

110

107

27

186 189

201

10

198

196

115

181

168

187

41

183

29 191

4 34

37

109

195

194

204

111

197

22

182

23

28

114

113

203

199

42

117

39

180

173

116

35

177

175

38

108

188

179

176

43

174

170

40

112

169

178

172

33

193

36

200

24

167

-77° -77°5' -77°10'

38°40'

VIR

GINIA

M

A

R

Y

L

A

N

D

UTR

LTR

Pomonkey Creek

Dogue Creek

Gunston

Cove

Potomac River

Piscataway

Creek

Swan

Creek

Little

HuntingCreek

U.S. Geological Survey

0 1 2 Miles 0.5

0 1 2 Kilometers 0.5

Figure 7. Location of each field bed in a continuous shoreline survey from Swan Creek, Md., to Gunston Cove, Va., 2007. River segments are the upper tidal river (UTR) and lower tidal river (LTR).
Figures 15 Figure 8. Location of each field bed in a continuous shoreline survey from Mason Neck, Va., to Quantico Creek, Va., 2007.

EXPLANATION

Field bed and number

130131133

138139140141142

154158

99

96

97

223

217

120

218

98

164

207

143

161

183

144

84 82

93

88

119

92

165

115

163

181

94

162

106

213

157

91

212

95

206

2221

155

83

132

117 182

197 111

103

156

121

208

135

78

148

114

113

136

216

152

124

146

118

184

153

104

129

90

149

215

145

86

166

180

89

173

116

177

175

2222

209

210

214

100

179

134

150

85 176

127

87

122

211

123

159

128

1851

174

137

170

112

151

79

105

178

172

102

1852

101

77

81

126

76

205

147

110

171

1252

1251

-77°5' -77°10' -77°15' -77°20'

38°40'

38°35'

VIR

GINIA

M

A

R

Y

L

A

N

D

Potomac River

Quantico Creek

Powells

Creek

Neabsco Creek

Occoquan Bay

Belmont

Bay

Occoquan River

Mason Neck

Indian Head

Mat at woman

Creek

P mo

onkey Creek

Chicamuxen Creek

0 1 2 3 Miles 0.5

0 0.9 1.8 2.7 Kilometers

U.S. Geological Survey
16 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

EXPLANATION

Field bed and number

223

221

218 217

224

237 229

2222

227

225

2221

228

216

2402

215

226

220

219

2401

238

239

0 0.25 0.5 1 1.5 2 Miles

0 0.25 0.5 1 1.5 2 Kilometers

LTR

UOE

MARYLAND

VIRGINIA

Potomac River

Mallows

Bay

Quantico

Creek

Quantico

Chopawamsic

Creek

Chicamuxen

Creek

U.S. Geological Survey

Figure 9. Location of each field bed in a continuous shoreline survey near Quantico, Va., and Mallows Bay, Md., 2007. River 

segments are the lower tidal river (LTR) and upper oligohaline estuary (UOE).
Figures 17

EXPLANATION

Field bed and number

231

2362

59

233

60

50 232

68

61

230

237

54

67

55

69

57 58 56

53

229

70 75

63

65

52

71

234

235

72

73

66

51

49

74

62

64

2361

-77°10' -77°15' -77°20' -77°25'

38°25'38°20'

0 1 2 3 Miles 0.5

0 1 2 3 Kilometers 0.5 Potomac River

Potomac Creek

Aquia Creek

Wades Bay

VIRGINIA

MARYLAND

UOE and downstreamextent of study

Maryland Point

U.S. Geological Survey

Figure 10. Location of each field bed in a continuous shoreline survey from Wades Bay, Md., to Potomac Creek, Va., 2007. UOE is the upper oligohaline estuary river segment.
18 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac EXPLANATION Field bed and number 231 59 233 60 50 232 68 61 230 54 67 55 69 57 58 56 53 70 75 63 65 52 71 72 73 66 51 49 7462 64

-77°10' -77°15' -77°20'

38°25'38°20'

0 1 2 3 Miles 0.5

0 1 2 3 Kilometers 0.5

VIR

GINIA

M

A

R

Y

L

A

N

D

P

o

t

o

m

a

c

R

vi e

r

Maryland Point

Potomac Creek

Potomac River

Aquia Creek

UOE and downstreamextent of study P

O

T

O

M

A

C

RIV

E

R

Figure 11. Location of each field bed in a continuous shoreline survey from Aquia Creek, Va., to the end of the river segment, 2007. UOE is the upper oligohaline estuary river segment.
Figures 19

77°20' 15' 77°10' 77°5'

38°40'

38°35'

30'

38°25'

0 0.5 1 2 3 Miles

0 0.5 1 2 3 Kilometers

EXPLANATION

SAV beds with 1–10% water lettuce coverage

Observations of water lettuce in the channel

2-meter bathymetry

VIRGINIA

MARYLAND

WASHINGTON, D.C.

VIRGINIA

MARYLAND

LTR

UOE

Enlargement area

Potomac River

Powells Creek

Quantico Creek

Aquia Creek

Chicamuxen Creek

Mattawoman Creek

Occoquan Bay

Mallows Bay

Wades Bay

Mason Neck

Indian Head

Quantico

Blue is study area

EXPLANATION

Figure 12. Distribution of water lettuce in the tidal Potomac River between Mason Neck and Aquia Creek, Va., 2007. LTR, 

lower tidal river; SAV, submersed aquatic vegetation; UOE, upper oligohaline estuary; %, percent.
20 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

15' 77°10' 77°5' 77° 76°55'

38°55'

38°50'

45'

0 0.5 1 2 3 4 5 Miles

0 0.5 1 2 3 4 5 Kilometers

EXPLANATION

Harvest site

SAV density

1

2

3

4

Virginia Institute of Marine Science

WASHINGTON, D.C.

VIRGINIA

MARYLAND

Woodrow Wilson Bridge

Reagan

National

Airport

UTR and upstream

extent of study

Anacostia River

Potomac River

Broad Creek

Oxon Run

Kingman

Island

Hunting

Creek

Chain

Bridge

Note: SAV beds shown in figures 13, 14, and 15 were delineated by

VIMS based on aerial photographs, then digitized and classified for

ground cover density. Density was determined using the Crown

Density Scale adapted from Paine (1981). Bed densities range

from one to four with one corresponding to less than 10%

vegetation coverage, two representing between 10 and 40%

coverage, three representing between 41 and 70% coverage and

four corresponding to 71 to 100% coverage.

Figure 13. Distribution and density of submersed aquatic vegetation (SAV) and the locations of the aquatic plant management 

harvest sites in the tidal Potomac River from Washington, D.C., to Broad Creek, Md., 2007. UTR is the upper tidal river study segment.
Figures 21 Figure 14. Distribution and density of submersed aquatic vegetation (SAV) and the locations of the aquatic plant management harvest sites in the tidal Potomac River 

from Chopawamsic Creek, Va., to the downstream extent of the study, 2007. UOE is the upper oligohaline estuary study segment.

-76°55' -77° -77°5' -77°10' -77°15' -77°20' -77°25'

38°45'38°40'38°35'38°30'

0 1 2 3 4 5 Miles

0 1 2 3 4 5 Kilometers

Virginia Institute of Marine Science

VIRGINIA

MARYLAND

Po ot mac R vi er

Broad Creek

UTR

LTR

LTR

UOE

Chicamuxen Creek

Mattawoman Creek

OccoquanBay

Dogue Creek

GunstonCove

Occoquan River Belmont Bay

Neabsco Creek

Powells Creek

PomonkeyCreek

Ind ai n Head

Quantico

Quantico Creek

ChopawamsicCreek

Piscataway Creek

Swan Creek

Little Hunting Creek

Mason Neck

EXPLANATION

SAV density

Harvest site

1234

Note: SAV beds shown in figures 13, 14, and 15 were delineated by

VIMS based on aerial photographs, then digitized and classified for

ground cover density. Density was determined using the CrownDensity Scale adapted from Paine (1981). Bed densities range

from one to four with one corresponding to less than 10%vegetation coverage, two representing between 10 and 40%

coverage, three representing between 41 and 70% coverage and

four corresponding to 71 to 100% coverage.
22 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac EXPLANATION SAV density Harvest site

1234

-77° -77°5' -77°10' -77°15' -77°20' -77°25'

38°30'38°25'38°20'38°15'

VIR

GINIA

M

A

R

Y

L

A

N

D

Potomac River

ChopawamsicCreek

Aquia Creek

Potomac Creek

MarylandPoint

NanjemoyCreek

Port Tobacco

Wades Bay

UOE and downstreamextent of study Rt. 301

Br di ge

Virginia Institute of Marine Science

0 1 2 3 4 5 Miles

0 1 2 3 4 5 Kilometers

Note: SAV beds shown in figures 13, 14, and 15 were delineated by

VIMS based on aerial photographs, then digitized and classified forground cover density. Density was determined using the Crown

Density Scale adapted from Paine (1981). Bed densities range

from one to four with one corresponding to less than 10%

vegetation coverage, two representing between 10 and 40%

coverage, three representing between 41 and 70% coverage and

four corresponding to 71 to 100% coverage.

Figure 15. Distribution and density of submersed aquatic vegetation (SAV) and the locations of the aquatic plant management harvest sites in the tidal Potomac River from Broad Creek, Md., to Chopawamsic Creek, Va., 2007. The river segments are the upper tidal river (UTR), lower tidal river (LTR), and the upper oligohaline estuary (UOE).
Figures 23

0

10

20

30

40

50

60

198519871989199119931995199719992001200320052007

UTR LTR UOE

Percent of available habitat with SAV

Year

EXPLANATION

Figure 16. Percent of available habitat (area less than 2 meters in depth) that was 

vegetated in each river segment (UTR, LTR, and UOE) from 1985 to 2007. The UTR, 

LTR, and UOE have 2,956, 5,173, and 3,355 hectares of available habitat, respectively. 

UTR, upper tidal river; LTR, lower tidal river; UOE, upper oligohaline estuary; SAV, 

submersed aquatic vegetation.

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

198519871989199119931995199719992001200320052007

UTR LTR UOE

EXPLANATION

Year

SAV area (ha)

Figure 17. Area occupied by submersed aquatic vegetation (SAV) for each river 

segment (UTR, LTR, and UOE) from 1985 to 2007. SAV area from Virginia Institute of 

Marine Science (Orth and others, 2008) except from U.S. Geological Survey in 1988 

(Rybicki and Landwehr, 2007). UTR, upper tidal river; LTR, lower tidal river; UOE, 

upper oligohaline estuary; ha, hectare.
24 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

8/21/2007 1 USGS Mt. Vernon 3 9.0 30.0 0.0 60.0 1.0 0.0 0.0 0.0 0.0 0.93

8/21/2007 2 USGS Mt. Vernon 4 18.0 25.0 0.0 53.0 1.0 2.0 1.0 0.0 0.0 1.16

8/21/2007 3 USGS Mt. Vernon 4 25.0 20.0 5.0 20.0 0.0 10.0 20.0 0.0 0.0 1.69

8/21/2007 4 USGS Mt. Vernon 2 60.0 0.0 0.0 20.0 20.0 0.0 0.0 0.0 0.0 0.95

8/21/2007 5 USGS Mt. Vernon 4 25.0 25.0 0.0 30.0 8.0 0.0 12.0 0.0 0.0 1.51

8/21/2007 6 USGS Mt. Vernon 4 69.0 15.0 0.0 10.0 1.0 0.0 5.0 0.0 0.0 0.97

8/21/2007 7 USGS Mt. Vernon 4 2.0 48.0 4.0 25.0 16.0 0.0 5.0 0.0 0.0 1.35

8/21/2007 8 USGS Mt. Vernon 3 11.0 58.0 0.0 28.0 3.0 0.0 0.0 0.0 0.0 1.02

8/21/2007 9 USGS Mt. Vernon 1 3.0 33.5 0.0 30.0 0.0 0.0 33.5 0.0 0.0 1.20

8/21/2007 10 USGS Mt. Vernon 3 40.0 0.0 1.0 1.0 35.0 23.0 0.0 0.0 0.0 1.16

8/21/2007 11 USGS Mt. Vernon 4 44.5 4.0 0.0 22.0 20.0 9.0 0.5 0.0 0.0 1.39

8/21/2007 12 USGS Mt. Vernon 3 70.0 10.0 20.0 0.0 0.0 0.0 0.0 0.0 0.0 0.80

8/21/2007 13 USGS Mt. Vernon/Alex 4 40.0 7.0 0.0 43.0 7.0 1.0 2.0 0.0 0.0 1.23

8/21/2007 14 USGS Mt. Vernon/Alex 4 32.5 0.0 0.5 30.0 20.0 15.0 2.0 0.0 0.0 1.44

8/21/2007 15 USGS Mt. Vernon/Alex 1 0.0 0.0 0.0 50.0 0.0 0.0 50.0 0.0 0.0 0.69

8/21/2007 16 USGS Mt. Vernon/Alex 4 94.0 0.0 0.0 3.0 3.0 0.0 0.0 0.0 0.0 0.27

8/21/2007 17 USGS Mt. Vernon/Alex 4 70.0 0.0 0.0 10.0 20.0 0.0 0.0 0.0 0.0 0.80

8/21/2007 18 USGS Mt. Vernon/Alex 4 70.0 0.0 0.0 20.0 10.0 0.0 0.0 0.0 0.0 0.80

8/21/2007 19 USGS Mt. Vernon/Alex 3 46.0 0.0 0.0 50.0 3.0 0.0 1.0 0.0 0.0 0.86

8/21/2007 20 USGS Mt. Vernon/Alex 3 70.0 0.0 0.0 10.0 20.0 0.0 0.0 0.0 0.0 0.80

8/22/2007 21 USGS Mt. Vernon 4 15.0 20.0 3.0 41.0 12.0 5.0 4.0 0.0 0.0 1.61

8/22/2007 22 USGS Mt. Vernon 4 15.0 0.0 0.0 80.0 1.0 3.0 1.0 0.0 0.0 0.66

8/22/2007 23 USGS Mt. Vernon 4 5.0 5.0 1.0 76.0 1.0 10.0 2.0 0.0 0.0 0.91

8/22/2007 24 USGS Mt. Vernon 3 2.0 2.0 1.0 81.0 2.0 2.0 10.0 0.0 0.0 0.76

8/22/2007 25 USGS Mt. Vernon 2 0.0 25.0 0.0 35.0 5.0 0.0 35.0 0.0 0.0 1.23

8/22/2007 26 USGS Mt. Vernon 4 24.0 7.0 1.0 51.0 7.0 7.0 3.0 0.0 0.0 1.40

8/22/2007 27 USGS Mt. Vernon 4 0.0 6.0 0.0 80.0 2.0 2.0 10.0 0.0 0.0 0.73

8/22/2007 28 USGS Mt. Vernon 4 10.0 20.0 1.0 54.0 0.0 0.0 15.0 0.0 0.0 1.22

8/22/2007 29 USGS Mt. Vernon 3 0.0 0.0 0.0 50.0 0.0 0.0 50.0 0.0 0.0 0.69
Table 1 25

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

8/22/2007 30 USGS Mt. Vernon 4 15.0 30.0 5.0 30.0 10.0 0.0 10.0 0.0 0.0 1.62

8/22/2007 31 USGS Mt. Vernon 4 29.0 15.0 0.5 10.0 30.5 0.0 15.0 0.0 0.0 1.55

8/22/2007 32 USGS Mt. Vernon 4 35.0 20.0 0.0 10.0 28.0 2.0 5.0 0.0 0.0 1.50

8/22/2007 33 USGS Mt. Vernon 4 56.0 0.0 2.0 0.0 39.0 2.0 1.0 0.0 0.0 0.89

8/22/2007 34 USGS Mt. Vernon 4 10.0 10.0 1.0 50.0 24.0 5.0 0.0 0.0 0.0 1.35

8/22/2007 35 USGS Mt. Vernon 4 69.0 10.0 0.0 10.0 10.0 0.0 1.0 0.0 0.0 0.99

8/22/2007 36 USGS Mt. Vernon 3 90.0 0.0 0.0 5.0 0.0 0.0 5.0 0.0 0.0 0.39

8/22/2007 37 USGS Mt. Vernon 4 50.0 10.0 3.0 10.0 26.0 1.0 0.0 0.0 0.0 1.31

8/22/2007 38 USGS Mt. Vernon 2 50.0 0.0 0.0 50.0 0.0 0.0 0.0 0.0 0.0 0.69

8/22/2007 39 USGS Mt. Vernon 4 60.0 10.0 5.0 15.0 10.0 0.0 0.0 0.0 0.0 1.20

8/22/2007 40 USGS Mt. Vernon 4 70.0 0.0 0.0 25.0 5.0 0.0 0.0 0.0 0.0 0.75

8/22/2007 41 USGS Mt. Vernon 4 56.5 5.0 0.0 14.0 24.0 0.0 0.5 0.0 0.0 1.12

8/22/2007 42 USGS Mt. Vernon 4 23.0 15.0 1.0 34.5 25.0 1.0 0.5 0.0 0.0 1.45

8/22/2007 43 USGS Mt. Vernon/Alex 4 15.0 9.0 0.0 50.0 25.0 1.0 0.0 0.0 0.0 1.24

8/22/2007 44 USGS Mt. Vernon/Alex 4 10.0 10.0 0.0 63.0 14.0 1.0 2.0 0.0 0.0 1.15

8/22/2007 45 USGS Mt. Vernon/Alex 2 0.0 0.0 0.0 80.0 0.0 0.0 20.0 0.0 0.0 0.50

8/22/2007 46 USGS Mt. Vernon/Alex 4 55.0 0.0 5.0 25.0 10.0 0.0 5.0 0.0 0.0 1.21

8/22/2007 47 USGS Mt. Vernon/Alex 4 20.0 0.0 0.0 65.0 15.0 0.0 0.0 0.0 0.0 0.89

8/22/2007 48 USGS Mt. Vernon/Alex 2 10.0 10.0 0.0 0.0 0.0 0.0 80.0 0.0 0.0 0.64

8/27/2007 49 USGS Widewater 4 15.0 25.0 5.0 25.0 25.0 5.0 0.0 0.0 0.0 1.62

8/27/2007 50 USGS Widewater 4 5.0 86.0 2.0 2.0 3.0 2.0 0.0 0.0 0.0 0.62

8/27/2007 51 USGS Widewater 4 25.0 41.0 1.0 30.0 1.0 1.0 1.0 0.0 0.0 1.26

8/27/2007 52 USGS Widewater 4 51.5 25.0 10.0 5.0 5.0 0.5 3.0 0.0 0.0 1.35

8/27/2007 53 USGS Widewater 4 15.0 47.5 30.0 5.0 1.0 1.0 0.5 0.0 0.0 1.27

8/27/2007 54 USGS Widewater 4 15.0 33.5 15.0 5.0 30.0 1.0 0.5 0.0 0.0 1.52

8/27/2007 55 USGS Widewater 4 1.0 59.0 10.0 5.0 5.0 5.0 15.0 0.0 0.0 1.32

8/27/2007 56 USGS Widewater 4 30.0 33.0 2.0 20.0 5.0 5.0 5.0 0.0 0.0 1.58
26 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued Survey date Field bed number Data source USGS quadrangle Density class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div 8/27/2007 57 USGS Widewater 4 0.5 42.0 2.0 35.0 10.0 10.0 0.5 0.0 0.0 1.32 8/27/2007 58 USGS Widewater 4 15.0 48.0 15.0 2.0 6.0 7.0 7.0 0.0 0.0 1.54 8/27/2007 59 USGS Widewater 4 25.0 48.0 15.0 1.0 0.5 0.5 10.0 0.0 0.0 1.31 8/27/2007 60 USGS Widewater 4 0.0 90.0 5.0 0.0 5.0 0.0 0.0 0.0 0.0 0.39 8/27/2007 61 USGS Widewater 4 0.0 85.5 5.0 4.0 0.0 0.5 5.0 0.0 0.0 0.59 8/27/2007 62 USGS Passapatanzy 2 0.0 98.5 0.0 0.5 0.0 0.5 0.5 0.0 0.0 0.09 8/27/2007 63 USGS Passapatanzy 2 0.5 95.5 0.5 0.5 0.5 0.5 0.0 0.0 2.0a 0.25 8/27/2007 64 USGS Passapatanzy 4 1.0 5.0 88.0 1.0 0.0 0.0 5.0 0.0 0.0 0.50 8/27/2007 65 USGS Passapatanzy 4 0.0 83.5 1.0 10.0 2.0 0.5 3.0 0.0 0.0 0.64 8/27/2007 66 USGS Passapatanzy 4 0.5 0.0 94.0 0.5 0.0 0.0 5.0 0.0 0.0 0.26 8/27/2007 67 USGS Passapatanzy 4 94.5 1.0 2.0 1.0 1.0 0.5 0.0 0.0 0.0 0.30 8/27/2007 68 USGS Passapatanzy 4 89.0 1.0 1.0 3.0 5.0 0.5 0.5 0.0 0.0 0.50 8/27/2007 69 USGS Passapatanzy 4 93.0 0.5 0.0 0.5 5.0 0.5 0.5 0.0 0.0 0.32 8/27/2007 70 USGS Passapatanzy 4 75.5 0.5 3.0 10.0 10.0 0.0 1.0 0.0 0.0 0.85 8/27/2007 71 USGS Passapatanzy 4 40.0 0.5 0.0 15.0 43.0 0.5 1.0 0.0 0.0 1.11 8/27/2007 72 USGS Passapatanzy 4 44.3 0.5 0.0 10.0 44.3 1.0 0.0 0.0 0.0 1.02 8/27/2007 73 USGS Passapatanzy 4 15.0 33.0 0.0 15.0 33.5 1.0 2.0 0.0 0.5b 1.45 8/27/2007 74 USGS Passapatanzy 4 68.0 10.0 0.0 1.0 20.0 0.0 1.0 0.0 0.0 0.91 8/27/2007 75 USGS Passapatanzy 0 25.0 39.5 0.5 25.0 9.0 0.5 0.5 0.0 0.0 1.36 9/5/2007 76 USGS Indian Head 4 97.5 0.5 0.0 1.0 1.0 0.0 0.0 0.0 0.0 0.14 9/5/2007 77 USGS Ft. Belvoir 4 1.0 0.5 97.0 0.5 1.0 0.0 0.0 0.0 0.0 0.17 9/5/2007 78 USGS Ft. Belvoir 2 15.0 0.5 68.0 0.5 15.0 0.0 0.5 0.0 0.5c 0.94 9/5/2007 79 USGS Ft. Belvoir 4 48.5 0.5 0.5 50.0 0.5 0.0 0.0 0.0 0.0 0.78 9/5/2007 80 USGS Ft. Belvoir 3 5.0 80.0 5.0 5.0 5.0 0.0 0.0 0.0 0.0 0.78 9/5/2007 81 USGS Ft. Belvoir 1 5.0 85.0 0.0 5.0 5.0 0.0 0.0 0.0 0.0 0.59

9/5/2007 82 USGS Ft. Belvoir 4 5.0 10.0 5.0 1.0 78.0 0.0 0.0 1.0 0.0 0.82

a sago pondweedb curly pondweedc chara
Table 1 27

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

9/5/2007 83 USGS Ft. Belvoir 4 74.0 5.0 10.0 5.0 5.0 0.0 0.0 1.0 0.0 0.95

9/5/2007 84 USGS Ft. Belvoir 4 65.0 5.0 0.0 15.0 15.0 0.0 0.0 0.0 0.0 1.00

9/5/2007 85 USGS Ft. Belvoir 4 85.0 5.0 0.0 5.0 5.0 0.0 0.0 0.0 0.0 0.59

9/5/2007 86 USGS Ft. Belvoir 4 47.5 5.0 5.0 20.0 20.0 0.0 0.0 0.5 2.0d 1.40

9/5/2007 87 USGS Ft. Belvoir 4 80.0 5.0 0.0 8.0 7.0 0.0 0.0 0.0 0.0 0.72

9/5/2007 88 USGS Ft. Belvoir 4 10.0 5.0 0.0 10.0 74.0 1.0 0.0 0.0 0.0 0.88

9/5/2007 89 USGS Ft. Belvoir 4 79.0 1.0 0.0 10.0 10.0 0.0 0.0 0.0 0.0 0.69

9/5/2007 90 USGS Ft. Belvoir 4 59.0 5.0 0.0 10.0 25.0 1.0 0.0 0.0 0.0 1.08

9/5/2007 91 USGS Ft. Belvoir 4 5.0 10.0 0.0 25.0 60.0 0.0 0.0 0.0 0.0 1.03

9/5/2007 92 USGS Ft. Belvoir 2 15.0 5.0 0.0 20.0 60.0 0.0 0.0 0.0 0.0 1.06

9/5/2007 93 USGS Ft. Belvoir 4 5.0 45.0 0.0 45.0 5.0 0.0 0.0 0.0 0.0 1.02

9/5/2007 94 USGS Ft. Belvoir 4 0.5 84.0 0.0 15.0 0.5 0.0 0.0 0.0 0.0 0.48

9/5/2007 95 USGS Ft. Belvoir 4 55.0 5.0 0.0 40.0 0.0 0.0 0.0 0.0 0.0 0.85

9/5/2007 96 USGS Ft. Belvoir 4 70.0 20.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.80

9/5/2007 97 USGS Ft. Belvoir 3 10.0 80.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.64

9/5/2007 98 USGS Ft. Belvoir 4 2.0 0.5 94.0 1.0 2.0 0.0 0.5 0.0 0.0 0.31

9/5/2007 99 USGS Ft. Belvoir 4 93.5 0.5 5.0 0.5 0.5 0.0 0.0 0.0 0.0 0.29

9/5/2007 100 USGS Ft. Belvoir 4 2.0 0.5 94.5 1.0 2.0 0.0 0.0 0.0 0.0 0.28

9/5/2007 101 USGS Ft. Belvoir 4 94.5 0.5 0.0 2.0 3.0 0.0 0.0 0.0 0.0 0.26

9/5/2007 102 USGS Ft. Belvoir 2 0.0 5.0 90.0 0.0 5.0 0.0 0.0 0.0 0.0 0.39

9/5/2007 103 USGS Ft. Belvoir 4 4.0 0.5 1.0 0.0 94.0 0.0 0.5 0.0 0.0 0.29

9/5/2007 104 USGS Ft. Belvoir 4 43.0 0.5 1.0 5.0 49.5 0.0 1.0 0.0 0.0 0.98

9/5/2007 105 USGS Ft. Belvoir 1 30.0 0.0 30.0 20.0 20.0 0.0 0.0 0.0 0.0 1.37

9/5/2007 106 USGS Ft. Belvoir 4 99.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.06

9/6/2007 107 USGS Mt. Vernon 4 85.0 2.0 3.0 3.0 2.0 2.0 3.0 0.0 0.0 0.69

9/6/2007 108 USGS Mt. Vernon 4 74.0 5.0 1.0 5.0 5.0 5.0 5.0 0.0 0.0 1.02

9/6/2007 109 USGS Mt. Vernon 4 20.0 1.0 1.0 20.0 30.0 5.0 23.0 0.0 0.0 1.58

9/6/2007 110 USGS Mt. Vernon 4 40.0 1.0 1.0 20.0 20.0 5.0 13.0 0.0 0.0 1.52

d redhead grass
28 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued Survey date Field bed number Data source USGS quadrangle Density class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div 9/6/2007 111 USGS Mt. Vernon 4 10.0 33.8 2.0 10.0 10.0 0.5 33.8 0.0 0.0 1.53 9/6/2007 112 USGS Mt. Vernon 4 90.0 5.0 1.0 2.0 1.0 0.5 0.5 0.0 0.0 0.47 9/6/2007 113 USGS Mt. Vernon 4 10.0 39.3 0.5 10.0 0.5 0.5 39.3 0.0 0.0 1.27 9/6/2007 114 USGS Mt. Vernon 4 40.0 25.0 3.0 5.0 1.0 2.0 24.0 0.0 0.0 1.43 9/6/2007 115 USGS Mt. Vernon 4 83.5 10.0 0.5 1.0 0.0 0.0 5.0 0.0 0.0 0.60 9/6/2007 116 USGS Mt. Vernon 4 10.0 79.0 0.0 0.0 0.0 1.0 10.0 0.0 0.0 0.69 9/6/2007 117 USGS Mt. Vernon 4 30.0 5.0 5.0 30.0 5.0 0.0 25.0 0.0 0.0 1.52 9/6/2007 118 USGS Mt. Vernon 4 30.0 47.0 1.0 5.0 1.0 1.0 15.0 0.0 0.0 1.29 9/6/2007 119 USGS Indian Head 1 0.0 50.0 0.0 0.0 0.0 0.0 50.0 0.0 0.0 0.69 9/6/2007 120 USGS Indian Head 4 88.5 5.0 0.0 0.5 0.5 0.5 5.0 0.0 0.0 0.49 9/6/2007 121 USGS Indian Head 4 80.5 10.0 0.5 2.0 2.0 0.0 5.0 0.0 0.0 0.74 9/6/2007 122 USGS Indian Head 3 20.0 10.0 5.0 5.0 55.0 1.0 4.0 0.0 0.0 1.36 9/6/2007 123 USGS Indian Head 4 40.0 15.0 2.0 0.0 40.0 2.0 1.0 0.0 0.0 1.22 9/6/2007 124 USGS Indian Head 4 70.0 10.0 0.0 0.0 15.0 1.0 4.0 0.0 0.0 0.94 9/6/2007 1251 USGS Indian Head 3 24.8 24.8 0.5 0.5 24.8 0.0 24.8 0.0 0.0 1.44 9/6/2007 1252 USGS Indian Head 3 24.8 24.8 0.5 0.5 24.8 0.0 24.8 0.0 0.0 1.44 9/6/2007 126 USGS Indian Head 4 84.0 0.0 1.0 5.0 5.0 0.0 5.0 0.0 0.0 0.64 9/6/2007 127 USGS Indian Head 1 0.0 50.0 0.0 0.0 0.0 0.0 50.0 0.0 0.0 0.69 9/6/2007 128 USGS Indian Head 2 20.0 20.0 0.0 20.0 20.0 0.0 20.0 0.0 0.0 1.61 9/6/2007 129 USGS Indian Head 1 0.0 1.0 1.0 0.0 1.0 0.0 97.0 0.0 0.0 0.17 9/6/2007 130 USGS Indian Head 65.0 15.0 5.0 0.0 10.0 0.0 5.0 0.0 0.0 1.09 9/25/2007 131 USGS Mattawoman Cr. 4 25.0 29.5 0.0 25.0 19.0 0.5 1.0 0.0 0.0 1.44 9/25/2007 132 USGS Mattawoman Cr. 2 1.0 76.0 0.0 20.0 3.0 0.0 0.0 0.0 0.0 0.68 9/25/2007 133 USGS Mattawoman Cr. 4 5.0 50.0 0.0 30.0 15.0 0.0 0.0 0.0 0.0 1.14 9/25/2007 134 USGS Mattawoman Cr. 4 70.0 15.0 3.0 11.0 0.0 0.0 1.0 0.0 0.0 0.93

9/25/2007 135 USGS Mattawoman Cr. 1 0.0 50.0 0.0 50.0 0.0 0.0 0.0 0.0 0.0 0.69

9/25/2007 136 USGS Mattawoman Cr. 4 8.0 40.0 2.0 50.0 0.0 0.0 0.0 0.0 0.0 0.99

9/25/2007 137 USGS Mattawoman Cr. 4 5.0 45.0 1.0 45.0 4.0 0.0 0.0 0.0 0.0 1.04

9/25/2007 138 USGS Mattawoman Cr. 4 0.0 34.0 15.0 30.0 20.0 0.0 1.0 0.0 0.0 1.38
Table 1 29

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

9/25/2007 139 USGS Mattawoman Cr. 4 0.0 30.0 0.0 40.0 0.0 30.0 0.0 0.0 0.0 1.09

9/25/2007 140 USGS Mattawoman Cr. 4 0.0 4.0 85.0 10.0 1.0 0.0 0.0 0.0 0.0 0.54

9/25/2007 141 USGS Mattawoman Cr. 4 2.0 45.0 0.0 30.0 8.0 15.0 0.0 0.0 0.0 1.29

9/25/2007 142 USGS Mattawoman Cr. 4 5.0 80.0 1.0 4.0 5.0 5.0 0.0 0.0 0.0 0.80

9/25/2007 143 USGS Mattawoman Cr. 4 0.0 15.0 0.0 50.0 5.0 30.0 0.0 0.0 0.0 1.14

9/25/2007 144 USGS Mattawoman Cr. 4 15.0 50.0 0.0 30.0 5.0 0.0 0.0 0.0 0.0 1.14

9/25/2007 145 USGS Mattawoman Cr. 4 5.0 20.0 0.0 40.0 5.0 30.0 0.0 0.0 0.0 1.35

9/25/2007 146 USGS Mattawoman Cr. 4 10.0 30.0 1.0 39.0 20.0 0.0 0.0 0.0 0.0 1.33

9/25/2007 147 USGS Mattawoman Cr. 4 10.0 30.0 20.0 30.0 10.0 0.0 0.0 0.0 0.0 1.50

9/25/2007 148 USGS Mattawoman Cr. 4 30.0 0.5 0.0 59.5 5.0 5.0 0.0 0.0 0.0 1.00

9/25/2007 149 USGS Mattawoman Cr. 4 50.0 15.0 0.0 30.0 5.0 0.0 0.0 0.0 0.0 1.14

9/25/2007 150 USGS Mattawoman Cr. 4 79.5 0.5 0.0 20.0 0.0 0.0 0.0 0.0 0.0 0.53

9/25/2007 151 USGS Mattawoman Cr. 4 60.0 0.0 0.0 40.0 0.0 0.0 0.0 0.0 0.0 0.67

9/25/2007 152 USGS Mattawoman Cr. 4 23.0 15.0 0.0 60.0 1.0 1.0 0.0 0.0 0.0 1.02

9/25/2007 153 USGS Mattawoman Cr. 4 10.0 30.0 0.0 40.0 10.0 10.0 0.0 0.0 0.0 1.42

9/25/2007 154 USGS Mattawoman Cr. 4 15.0 5.0 0.5 5.0 37.3 37.3 0.0 0.0 0.0 1.35

9/25/2007 155 USGS Mattawoman Cr. 4 63.5 5.0 2.0 19.0 10.0 0.5 0.0 0.0 0.0 1.09

9/25/2007 156 USGS Mattawoman Cr. 4 10.0 59.5 0.0 20.0 10.0 0.5 0.0 0.0 0.0 1.12

9/25/2007 157 USGS Mattawoman Cr. 4 0.0 40.0 2.0 48.0 10.0 0.0 0.0 0.0 0.0 1.03

9/25/2007 158 USGS Mattawoman Cr. 4 0.0 20.0 0.0 45.0 0.0 35.0 0.0 0.0 0.0 1.05

9/25/2007 159 USGS Mattawoman Cr. 4 8.0 15.0 59.5 15.0 1.0 1.0 0.5 0.0 0.0 1.20

9/25/2007 160 USGS Mattawoman Cr. 4 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00

9/25/2007 161 USGS Mattawoman Cr. 4 15.0 50.0 0.0 30.0 5.0 0.0 0.0 0.0 0.0 1.14

9/25/2007 162 USGS Mattawoman Cr. 4 0.0 39.5 0.5 30.0 0.0 30.0 0.0 0.0 0.0 1.12

9/25/2007 163 USGS Mattawoman Cr. 4 0.0 70.0 0.0 30.0 0.0 0.0 0.0 0.0 0.0 0.61

9/25/2007 164 USGS Mattawoman Cr. 4 2.0 70.0 0.0 20.0 0.0 8.0 0.0 0.0 0.0 0.85

9/25/2007 165 USGS Mattawoman Cr. 3 20.0 60.0 0.0 10.0 10.0 0.0 0.0 0.0 0.0 1.09

9/25/2007 166 USGS Mattawoman Cr. 4 30.0 20.0 30.0 20.0 0.0 0.0 0.0 0.0 0.0 1.37

10/4/2007 167 USGS Ft. Belvoir 4 59.5 15.0 5.0 15.0 2.0 0.5 3.0 0.0 0.0 1.24
30 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued Survey date Field bed number Data source USGS quadrangle Density class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div 10/4/2007 168 USGS Ft. Belvoir 2 30.0 0.0 0.0 40.0 25.0 5.0 0.0 0.0 0.0 1.22 10/4/2007 169 USGS Ft. Belvoir 4 5.0 35.0 1.0 44.0 5.0 10.0 0.0 0.0 0.0 1.30 10/4/2007 170 USGS Ft. Belvoir 4 3.0 80.0 1.0 10.0 3.0 3.0 0.0 0.0 0.0 0.77 10/4/2007 171 USGS Ft. Belvoir 4 2.0 65.0 25.0 5.0 1.0 2.0 0.0 0.0 0.0 0.98 10/4/2007 172 USGS Ft. Belvoir 4 1.0 2.0 42.0 5.0 49.0 1.0 0.0 0.0 0.0 1.03 10/4/2007 173 USGS Ft. Belvoir 4 10.0 48.0 10.0 1.0 30.0 0.0 1.0 0.0 0.0 1.27 10/4/2007 174 USGS Ft. Belvoir 4 30.0 1.0 30.0 1.0 38.0 0.0 0.0 0.0 0.0 1.18 10/4/2007 175 USGS Ft. Belvoir 4 20.0 1.0 57.0 1.0 20.0 0.0 1.0 0.0 0.0 1.10 10/4/2007 176 USGS Ft. Belvoir 4 45.0 10.0 35.0 5.0 5.0 0.0 0.0 0.0 0.0 1.26 10/4/2007 177 USGS Ft. Belvoir 4 20.0 20.0 39.0 10.0 10.0 0.5 0.5 0.0 0.0 1.52 10/4/2007 178 USGS Ft. Belvoir 3 5.0 5.0 80.0 5.0 5.0 0.0 0.0 0.0 0.0 0.78 10/4/2007 179 USGS Ft. Belvoir 4 2.0 5.0 85.0 2.0 5.0 0.0 1.0 0.0 0.0 0.64 10/4/2007 180 USGS Ft. Belvoir 4 5.0 5.0 77.0 2.0 5.0 1.0 5.0 0.0 0.0 0.92 10/4/2007 181 USGS Ft. Belvoir 4 1.0 55.0 40.0 1.0 1.0 1.0 1.0 0.0 0.0 0.93 10/4/2007 182 USGS Ft. Belvoir 2 0.0 90.0 0.0 0.0 0.0 0.0 10.0 0.0 0.0 0.33 10/4/2007 183 USGS Ft. Belvoir 4 5.0 87.0 1.0 5.0 0.0 1.0 1.0 0.0 0.0 0.56 10/4/2007 184 USGS Indian Head 4 0.5 96.5 0.5 0.5 0.0 0.0 2.0 0.0 0.0 0.19 10/4/2007 1851 USGS Indian Head 1 0.0 97.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 0.13 10/4/2007 1852 USGS Indian Head 1 0.0 97.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 0.13 10/4/2007 186 USGS Mt. Vernon 4 6.0 90.0 0.0 1.0 1.0 1.0 1.0 0.0 0.0 0.45 10/4/2007 187 USGS Mt. Vernon 4 75.5 15.0 1.0 5.0 0.0 3.0 0.5 0.0 0.0 0.82 10/4/2007 188 USGS Mt. Vernon 4 0.0 59.0 19.0 11.0 1.0 0.0 10.0 0.0 0.0 1.15 10/4/2007 189 USGS Mt. Vernon 4 46.0 30.0 3.0 15.0 0.0 4.0 2.0 0.0 0.0 1.32 10/4/2007 190 USGS Mt. Vernon 4 10.0 34.0 5.0 49.0 0.0 1.0 1.0 0.0 0.0 1.19 10/4/2007 191 USGS Mt. Vernon 4 26.0 35.0 10.0 5.0 20.0 2.0 2.0 0.0 0.0 1.58

10/4/2007 192 USGS Mt. Vernon 4 20.0 10.0 1.0 9.0 29.8 29.8 0.0 0.0 0.5e 1.56

10/4/2007 193 USGS Mt. Vernon 2 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00

e curly pondweed
Table 1 31

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

10/4/2007 194 USGS Mt. Vernon 4 15.0 10.0 0.0 36.0 20.0 19.0 0.0 0.0 0.0 1.52

10/4/2007 195 USGS Mt. Vernon 4 10.0 50.0 0.0 35.0 5.0 0.0 0.0 0.0 0.0 1.09

10/4/2007 196 USGS Mt. Vernon 4 5.0 59.5 3.0 30.0 1.0 1.0 0.5 0.0 0.0 1.04

10/4/2007 197 USGS Mt. Vernon 3 0.0 60.0 0.0 40.0 0.0 0.0 0.0 0.0 0.0 0.67

10/4/2007 198 USGS Mt. Vernon 4 75.0 14.0 1.0 5.0 5.0 0.0 0.0 0.0 0.0 0.84

10/4/2007 199 USGS Mt. Vernon 4 90.0 5.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.39

10/4/2007 200 USGS Mt. Vernon 4 70.0 0.0 0.0 0.0 15.0 15.0 0.0 0.0 0.0 0.82

10/4/2007 201 USGS Mt. Vernon 4 13.0 13.0 0.0 50.0 12.0 12.0 0.0 0.0 0.0 1.39

10/4/2007 202 USGS Mt. Vernon 4 15.0 69.0 0.0 15.0 0.5 0.5 0.0 0.0 0.0 0.88

10/4/2007 203 USGS Mt. Vernon 4 10.0 15.0 0.0 10.0 5.0 60.0 0.0 0.0 0.0 1.20

10/4/2007 204 USGS Mt. Vernon 4 55.0 25.0 1.0 0.0 1.0 18.0 0.0 0.0 0.0 1.08

10/9/2007 205 USGS Quantico 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00

10/9/2007 206 USGS Quantico 4 10.0 5.0 35.0 15.0 35.0 0.0 0.0 0.0 0.0 1.40

10/9/2007 207 USGS Quantico 4 15.0 10.0 10.0 40.0 25.0 0.0 0.0 0.0 0.0 1.46

10/9/2007 208 USGS Quantico 4 29.8 5.0 5.0 29.8 29.8 0.5 0.0 0.0 0.0 1.41

10/9/2007 209 USGS Quantico 4 1.0 1.0 96.0 1.0 1.0 0.0 0.0 0.0 0.0 0.22

10/9/2007 210 USGS Quantico 4 5.0 5.0 74.0 5.0 5.0 0.0 5.0 0.0 1.0e 1.02

10/9/2007 211 USGS Quantico 1 0.0 15.0 40.0 15.0 0.0 0.0 30.0 0.0 0.0 1.30

10/9/2007 212 USGS Quantico 4 18.3 18.3 15.0 18.3 15.0 0.0 15.0 0.0 0.0 1.79

10/9/2007 213 USGS Quantico 4 39.5 5.0 30.0 15.0 5.0 0.5 5.0 0.0 0.0 1.49

10/9/2007 214 USGS Quantico 4 32.3 5.0 5.0 32.3 20.0 0.5 5.0 0.0 0.0 1.53

10/9/2007 215 USGS Quantico 4 20.0 45.0 5.0 20.0 5.0 0.0 5.0 0.0 0.0 1.45

10/9/2007 216 USGS Quantico 4 20.0 79.5 0.0 0.0 0.0 0.0 0.5 0.0 0.0 0.53

10/9/2007 217 USGS Quantico 4 5.0 20.0 20.0 20.0 34.5 0.0 0.5 0.0 0.0 1.51

10/9/2007 218 USGS Quantico 4 44.5 15.0 20.0 15.0 5.0 0.0 0.5 0.0 0.0 1.43

10/9/2007 219 USGS Quantico 4 10.0 10.0 20.0 33.0 25.0 1.0 1.0 0.0 0.0 1.59

10/9/2007 220 USGS Quantico 4 20.0 29.8 5.0 29.8 10.0 0.5 5.0 0.0 0.0 1.60

10/9/2007 221 USGS Quantico 4 24.0 25.0 1.0 20.0 5.0 5.0 20.0 0.0 0.0 1.68

10/10/2007 2221 USGS Indian Head 4 5.0 39.0 1.0 39.0 5.0 10.0 1.0 0.0 0.0 1.36
32 The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued Survey date Field bed number Data source USGS quadrangle Density class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div 10/10/2007 2222 USGS Indian Head 4 5.0 39.0 1.0 39.0 5.0 10.0 1.0 0.0 0.0 1.36 10/10/2007 223 USGS Indian Head 4 0.5 50.5 0.5 48.0 0.5 0.0 0.0 0.0 0.0 0.78 10/10/2007 224 USGS Quantico 4 0.5 30.0 0.5 25.0 0.0 5.0 39.0 0.0 0.0 1.28 10/10/2007 225 USGS Widewater 4 0.0 30.0 5.0 25.0 0.0 0.5 39.5 0.0 0.0 1.25 10/10/2007 226 USGS Widewater 4 5.0 30.0 5.0 30.0 5.0 0.0 25.0 0.0 0.0 1.52 10/10/2007 227 USGS Widewater 4 0.0 42.3 5.0 10.0 0.0 0.5 42.3 0.0 0.0 1.13 10/10/2007 228 USGS Widewater 4 0.5 42.0 5.0 4.0 1.0 5.0 42.5 0.0 0.0 1.23 10/10/2007 229 USGS Widewater 4 5.0 26.7 15.0 26.7 0.0 0.0 26.7 0.0 0.0 1.49 10/10/2007 230 USGS Widewater 4 1.0 40.0 10.0 10.0 1.0 3.0 35.0 0.0 0.0 1.39 10/10/2007 231 USGS Widewater 4 5.0 39.5 20.0 10.0 0.5 5.0 20.0 0.0 0.0 1.57 10/10/2007 232 USGS Widewater 4 0.0 73.5 15.0 1.0 10.0 0.5 0.0 0.0 0.0 0.81 10/10/2007 233 USGS Widewater 4 5.0 79.0 1.0 5.0 5.0 5.0 0.0 0.0 0.0 0.83 10/10/2007 234 USGS Widewater 4 75.0 10.0 0.0 5.0 5.0 5.0 0.0 0.0 0.0 0.90 10/10/2007 235 USGS Widewater 4 29.8 10.0 0.0 29.8 29.8 0.5 0.0 0.0 0.0 1.34 10/10/2007 2361 USGS Widewater 4 69.0 0.5 0.0 20.0 10.0 0.5 0.0 0.0 0.0 0.86 10/10/2007 2362 USGS Widewater 4 69.0 0.5 0.0 20.0 10.0 0.5 0.0 0.0 0.0 0.86 10/10/2007 237 USGS Widewater 4 0.0 68.0 30.0 1.0 0.0 0.0 1.0 0.0 0.0 0.72 10/10/2007 238 USGS Widewater 4 72.0 1.0 1.0 20.0 0.0 1.0 5.0 0.0 0.0 0.85 10/10/2007 239 USGS Widewater 4 1.0 1.0 1.0 70.0 5.0 20.0 2.0 0.0 0.0 0.94 10/10/2007 2401 USGS Widewater 4 0.5 48.0 40.0 10.0 0.5 0.0 1.0 0.0 0.0 1.05 10/10/2007 2402 USGS Widewater 4 0.5 48.0 40.0 10.0 0.5 0.0 1.0 0.0 0.0 1.05 10/4/2007 241 DDOE Alexandria 3 20.0 20.0 5.0 20.0 15.0 5.0 15.0 0.0 0.0 1.83 10/4/2007 242 DDOE Alexandria 2 30.0 5.0 0.0 25.0 30.0 0.0 10.0 0.0 0.0 1.45 9/25/2007 243 DDOE Alexandria 4 50.0 0.0 0.0 10.0 10.0 0.0 30.0 0.0 0.0 1.17 9/25/2007 244 DDOE Alexandria 3 10.0 0.0 0.0 15.0 5.0 0.0 70.0 0.0 0.0 0.91

9/25/2007 245 DDOE Alexandria 2 60.0 0.0 0.0 5.0 35.0 0.0 0.0 0.0 0.0 0.82

10/4/2007 246 DDOE Alexandria 4 30.0 20.0 10.0 20.0 10.0 0.0 10.0 0.0 0.0 1.70

10/4/2007 247 DDOE Alexandria 2 80.0 0.0 0.0 0.0 20.0 0.0 0.0 0.0 0.0 0.50
Table 1 33

Table 1. Percent canopy cover of each species and Shannon diversity index for field beds in the tidal Potomac River, 2007. Field bed numbers correspond to the numbers in figures 5 to 11. Density classes are USGS field data based on a Braun-Blanquet crown cover model where: 1 = 1 to 10%, 2 = 11 to 40%, 3 = 41 to 70%, and 4 = 71 to 100% cover. Percent cover of each species in a bed is abbreviated as: P_HV (hydrilla), P_MS (milfoil), P_VA (wild celery), P_CD (coontail), P_NM (naiad), P_NGU (southern naiad), P_HD (stargrass), P_PPU (slender pondweed), and Other (muskgrass, sago pondweed, or redhead grass). USGS is U.S. Geological Survey and DDOE is the District of Columbia District Department of Environment. Alex; Alexandria. Cr., Creek; Div, Shannon diversity index.—Continued

Survey date

Field 

bed 

number

Data 

source

USGS 

quadrangle

Density 

class P_HV P_MS P_VA P_CD P_NM P_NGU P_HD P_PPU Other Div

9/26/2007 248 DDOE Alexandria 1 60.0 0.0 0.0 20.0 20.0 0.0 0.0 0.0 0.0 0.95

10/18/2007 249 DDOE Alexandria 4 98.0 0.0 0.0 2.0 0.0 0.0 0.0 0.0 0.0 0.10

10/18/2007 250 DDOE DC West 3 80.0 0.0 0.0 0.0 10.0 0.0 10.0 0.0 0.0 0.64

9/4/2007 251 DDOE DC West 2 30.0 0.0 0.0 0.0 20.0 0.0 50.0 0.0 0.0 1.03

9/4/2007 252 DDOE DC West 1 10.0 0.0 0.0 0.0 10.0 0.0 80.0 0.0 0.0 0.64

9/4/2007 253 DDOE DC West 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.00

9/4/2007 254 DDOE DC West 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.00

9/4/2007 255 DDOE DC West 2 30.0 0.0 0.0 0.0 0.0 0.0 70.0 0.0 0.0 0.61

9/4/2007 256 DDOE DC West 2 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.00

9/4/2007 257 DDOE DC West 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.00

9/4/2007 258 DDOE DC West 2 70.0 0.0 0.0 0.0 0.0 0.0 30.0 0.0 0.0 0.61

9/4/2007 259 DDOE DC West 3 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.00

9/24/2007 260 DDOE DC West 2 30.0 0.0 0.0 0.0 0.0 0.0 70.0 0.0 0.0 0.61

9/24/2007 261 DDOE DC West 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00

9/24/2007 262 DDOE DC West 2 60.0 0.0 0.0 0.0 0.0 0.0 40.0 0.0 0.0 0.67

9/24/2007 263 DDOE DC West 2 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00

9/24/2007 264 DDOE DC West 4 98.0 0.0 0.0 0.0 0.0 0.0 2.0 0.0 0.0 0.10

9/24/2007 265 DDOE DC West 1 50.0 0.0 0.0 0.0 0.0 0.0 50.0 0.0 0.0 0.69

8/9/2007 266 DDOE DC West 4 50.0 0.0 0.0 0.0 10.0 0.0 40.0 0.0 0.0 0.94

8/9/2007 267 DDOE DC West 3 40.0 0.0 0.0 0.0 20.0 0.0 40.0 0.0 0.0 1.05

9/24/2007 268 DDOE DC West 1 20.0 0.0 20.0 0.0 0.0 0.0 60.0 0.0 0.0 0.95

9/5/2007 269 DDOE DC West 1 25.0 0.0 50.0 0.0 0.0 0.0 25.0 0.0 0.0 1.04

9/5/2007 270 DDOE Alexandria/

DC West

2 0.0 0.0 90.0 0.0 0.0 0.0 10.0 0.0 0.0 0.33

9/26/2007 271 DDOE Alexandria 4 90.0 0.0 0.0 0.0 0.0 0.0 10.0 0.0 0.0 0.33

9/26/2007 272 DDOE Alexandria 2 40.0 0.0 0.0 0.0 0.0 0.0 60.0 0.0 0.0 0.67

10/4/2007 273 DDOE Alexandria 2 0.0 0.0 0.0 15.0 5.0 0.0 80.0 0.0 0.0 0.61

10/4/2007 274 DDOE Alexandria 3 20.0 5.0 0.0 20.0 20.0 0.0 35.0 0.0 0.0 1.48
For additional information regarding this publication, contact:

U.S. Geological Survey

National Research Program,

 Eastern Region

432 National Center

Reston, VA 20192

http://water.usgs.gov/nrp/

Edited and prepared by:

USGS Science Publishing Network

Raleigh and Reston Publishing Service Centers

Campbell and others—The Distribution of Submersed Aquatic Vegetation and Water Lettuce in the Fresh and Oligohaline Tidal Potomac River, 2007—Open-File Report 2014–1259

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141259