People, Land and Water at the
Headwaters of the
Rappahannock River Basin

10 Least-protected subwatersheds: The Lower Rush

The Lower Rush subwatershed is an area of 2,855 acres or 4.46 square miles, just south of the town of Washington.  Map 18: Lower Rush Subwatershed Surface Water shows the Lower Rush with its surrounding subwatersheds, roads, and streams. 

When we assessed all 26 subwatersheds in the County, the Lower Rush was determined to be one of the least well protected.   Special aspects of interest in the Lower Rush include the following:

• The segment of the Rush River that flows into the Lower Rush subwatershed has been identified by the Virginia Department of Environmental Quality (DEQ) as “303d Impaired” for ecoli bacteria.
• The Rush River sometimes is at a very low flow or no flow.
• The Town of Washington has obtained a permit from VA DEQ to discharge the effluent from a public sewage treatment plant into the Rush River immediately upstream of the Lower Rush subwatershed.
• Landowners and residents in the Lower Rush subwatershed have indicated strong interest in the quality of the water in the Rush River and in the health of their watershed, as evidenced through their participation in public meetings on the subject, their participation in RappFLOW’s Upper Thornton Watershed survey of landowner concerns and values, and their volunteer work to assist in this study.
• The Lower Rush subwatershed includes a mix of agricultural, residential, and commercial land uses that are representative of the land uses in Rappahannock County.  By analyzing the Lower Rush subwatershed, we may identify factors and watershed management tools that will be useful to apply more broadly throughout the county and in similar rural Virginia watersheds.

10.1 Rush River and Tributary Streams

The Rush River has its headwaters in the Shenandoah National Park and flows about 12.5 miles through the Upper, Middle, and Lower Rush subwatersheds before its confluence with the Thornton River near Rock Mills.  Big Branch tributary joins the Rush at the northern edge of the Lower Rush subwatershed. See Map 17.

10.2 Lower Rush Easements

Map 21 shows easements (VOF) in the Lower Rush Subwatershed.  It shows all easements as of the May 2008 database, and in separate symbology those easements that were in place as of 2005.  This shows the growth in easement lands over the past three years.

10.3 Lower Rush Topography and Soils

Map 19 shows the topography of the subwatershed.  Most of the area is fairly flat, between 500 and 600 feet in elevation.  On the northwestern edge is (name) mountain, at elevation 1200 feet, and on the eastern edge is Long Mountain at 900 feet.

Map 20 shows the erodible soils on nonforested areas in the Lower Rush subwatershed.

10.4 Streams, ponds, wetlands and floodplains in the Lower Rush subwatershed.

There are a little over 15 miles of streams and about nine acres of ponds in the Lower Rush subwatershed, as calculated from the National Hydrology Database.  One small, unnamed tributary to the Rush River flows from the eastern side of the town of Washington.  Another small, unnamed stream flows from the western side of the town into Big Branch, which in turn is a tributary to the Rush.  On the basis of the National Wetlands Inventory we calculated there are only about 22 acres of wetlands in this subwatershed.  One-hundred-year floodplains as defined by FEMA are also shown in map 18.

The amount of water flowing in the Rush River varies greatly. From 1954 to 1977, the US Geological Survey had a water flow monitoring station on the Rush River just outside the town of Washington.  The meter recorded the cubic feet of water flow per second (cfps), and the average flow was recorded on a daily basis.  For that thirteen-year period, the average daily flow varied from a low of zero (0) cfps on many occasions, to a high of 1140 mean daily cfps on August 18, 1955.  The highest flow rate recorded was 2880 cfps on October 9, 1976.  The lowest annual mean was 7.70 cfps in 1966 and the highest annual mean was 30 in 1972.

All residents in the Lower Rush subwatershed obtain their drinking water from wells. Our survey of landowner values and concerns (see section 4 below) offers 12 water issues and respondents were asked to choose THREE of the most concern to them.  Out of these, 88% of respondents in the Lower Rush subwatershed chose “quality of well water” and 44% cited “adequate supply of good drinking water” as one of their biggest concerns. 

10.5 Water Quality – Rush River

Water quality data for the Rush River and its tributary streams are available from four main sources:

1. historical water quality data from the VA DEQ ambient monitoring station near the town of Washington;
2. information about the sources of e coli bacteria, collected by VA DEQ in conjunction with the Washington application for sewage effluent discharge;
3. Virginia Save Our Streams (SOS) invertebrate monitoring station at that same location;
4. data collected by RappFLOW volunteers in the spring of 2006 at 13 locations along the Rush River and tributaries. 

RappFLOW volunteers collecting water samples in Rush River in July 2006.  Photo by Ellie Clark.

10.5.1 DEQ Monitoring Data for Rush River

In 2004, the VA DEQ designated a segment of the Rush River  as “303d impaired” for fecal coliform bacteria.  Sufficient exceedances of the instantaneous fecal coliform bacteria criterion (4 of 17 samples - 23.5%) were recorded at DEQ's ambient water quality monitoring station 3-RUS005.66 at Route 211/522 to assess this stream segment as not supporting of the Recreation Use goal for the 2004 water quality assessment.

Graph 1 shows the historical data from the DEQ monitoring stations on the Rush River from 1990 to 2008 for fecal coliform, with the extremely high values shown. Fecal coliform bacteria shall not exceed a geometric mean of 200 fecal coliform bacteria per 100 mL of water for two or more samples over a calendar month Graph 2 shows more detail for the values below 500 colonies/100 ml.

 

Graph 1: Fecal coliform values from DEQ stations on Rush River.

 

Graph 2: Fecal coliform data from DEQ monitoring stations on Rush River, showing values up to 500 colonies per milliliter.

10.5.24 Sources of E. coli

“Bacterial source tracking” is a method used to identify the percentage of wildlife, human, livesk, and pet sources of E. coli within a water sample.  MapTech, a contractor to the VA DEQ, studied monthly water samples from the DEQ monitoring station on the Rush River outside the town of Washington between July 2004 and July 2005.  In general, on those occasions when the E. coli levels exceeded the state water quality standards (September 2004 and March 2005), the predominant source was livesk.  When E.coli levels did not exceed the standard, the predominant sources were wildlife, livesk, and pets.  In none of the cases was the majority source attributed to humans. [42]

The following is from the TMDL study.[43] This study attributes over 95% of the source of fecal coliform loadings in the Rush watershed to pastures.

A synopsis of the fecal coliform loads characterized and accounted for in the Rush River (VAN-E05R-01) watershed along with average fecal coliform production rates are shown in Table 3.33. The total fecal coliform production by all sources in the Rush River (VAN-E05R-01) watershed is 6.00x1015 cfu/yr.

Table 3.33. Potential fecal coliform sources and daily fecal coliform production by source in Rush River (VAN-E05R-01) watershed.

Based on the inventory of fecal coliform sources, a summary of the contributions made by the nonpoint sources to annual fecal coliform loading directly to the stream and to various land use categories is given in Table 3.34. Distribution of annual fecal coliform loading from nonpoint sources among the different land use categories is also given in Table 3.34.

From Table 3.34, it is clear in the Rush River (VAN-E05R-01) watershed that nonpoint source loadings to the land surface are more than 153 times as large as direct loadings to the streams, with pastures receiving about 96% of the total fecal coliform load. It could be prematurely assumed that most of the fecal coliform loading in streams originates from upland

Bacteria TMDLs for Rappahannock River Basin 3-33

sources, primarily from pastures. However, other factors such as precipitation (amount and pattern), manure application activities (time and method), type of waste (solid versus liquid manure), proximity to streams and environmental factors also impact the amount of fecal coliform from upland areas that reaches the stream. The HSPF model considers these factors when estimating fecal coliform loads to the receiving waters, as described in Chapter 4.

 

Table 3.34. Annual fecal coliform loadings to the stream and the various land use categories in the Rush River (VAN-E05R-01) watershed.

10.5.3 Macroinvertebrate data

The macroinvertebrate monitoring station on the Rush River is near the Old Mill off Library Road.  The table below shows the index for that site since 2001. 

10.5.4 RappFLOW water quality monitoring

In the winter of 2006, many residents and landowners in the Rush River watershed were concerned about water quality in the Rush River.  This concern was expressed in several meetings related to the town of Washington’s plan to discharge sewage effluent into the Rush River.  In response to these concerns, RappFLOW set up a program to monitor water quality at several locations along the main stem of the Rush River and its tributaries.  James Beckley of the VA DEQ assisted by training RappFLOW leaders in the use of equipment and materials for monitoring Dissolved Oxygen, pH, temperature, and E. Coli bacteria, and in establishing Quality Assurance Procedures so that the data will be useful to the DEQ.  Selection of locations for monitoring was based on several considerations, including the desire to identify potential sources of the bacterial impairment of the streams, to provide a baseline reading on Dissolved Oxygen at various locations before the sewage treatment plant is constructed, and accessibility of the sites by volunteer monitors.

Trained volunteers collected and summarized data in April, May, July, and August 2006, at sixteen locations along the Rush River and its tributaries.  Readings for E. coli in July are shown on Map 22: RappFLOW Monitoring E. coli.  Note that E. coli exceeded standards at several locations. Readings for Dissolved Oxygen in August are shown in Map 23: RappFLOW Monitoring Dissolved Oxygen. 

10.6 How is the land used in the Lower Rush Subwatershed?

The ways in which the land is used, especially the extent to which forest protects the streams, is the main determinant of the health of the watershed. 

10.6.1 Residential uses

There are an estimated 120 dwellings in the subwatershed.  At an average of 2.5 persons per dwelling (Census 2000), there are an estimated 300 residents.  This is a population density of approximately 67 persons per square mile.  By comparison, the overall county population density in 2000 was 26.2 persons per square mile.[44] 

10.6.2 Land Cover

Land cover in the subwatershed area can most easily be visualized through aerial photos.  Map 24 shows the aerial photo taken in 2002.

By analyzing the National Land Cover Database, (USGS 2002), we calculated that the Lower Rush subwatershed is approximately 46 percent forest cover, about 48 percent hay/pasture, about 3 percent low intensity residential, and contains small percentages of transitional land cover, industrial, row crops, open water, or wetlands.

10.6.3 Vegetation along Streams

There are about 360 acres of area within 100 feet of the streams in the Lower Rush subwatershed.  We used two methods to assess the vegetative cover of this buffer area.

Method 1: Aerial Photo. Using an aerial photo, we classified this stream buffer area as to whether it is fully vegetated (forest), partially vegetated, few or no trees, or a road crossing.  This result is shown in Map 9: Stream Buffers. Using this method, the approximate percentages of stream buffer areas in the lower Rush are shown in Table 7:

Table 7: Stream Buffer Vegetation in Lower Rush Subwatershed

Method 2: NLCD. We extracted a 100-foot buffer area along the streams from the National Land Cover Database and calculated the percentage of that buffer area that was classified as forest by the NLCD.  The result, 47.4 percent forested, correlates well with the results using the aerial photo method.  The aerial photo method is more accurate and more current than the NLCD  with respect to specific locations along the stream, but the overall percentage of forest cover is nearly the same using both methods. 

Map 25 shows the stream buffer vegetation in the Lower Rush Subwatershed.

10.6.4 Roads, Private Roads and Driveways in the Lower Rush

In addition to public roads, there are about 34 miles of private roads, lanes, driveways and farm roads in the Lower Rush subwatershed. 

10.6.5Road/Stream Intersections

Using the method described in section x above, the Lower Rush contains 12.26 acres of road/stream intersection area. The road/stream intersection area shown in Table 7 above is considerably greater (44 acres), because that analysis is based on the aerial photo which reveals farm roads and other private roads that are not included in the county roads map.

10.6.6 Stream Buffers and Land Use

In the Lower Rush subwatershed, most of the stream buffer areas that are unprotected by forest cover are found in areas of agricultural land use.  In most cases where streams are flowing through non-agricultural residential land use, they are in forest.  This is the case even on small residential parcels.  On the small residential parcels where a stream is flowing through the property, compromises to the stream buffer area are typically resulting from roads and driveway crossings.

There are approximately 210 parcels in the Lower Rush subwatershed.  Twenty-one parcels are 50 acres or greater.  The parcels that are 50 acres or more represent approximately 43% of the total Lower Rush subwatershed area.

10.6.7 Agricultural/Forestal Districts

As shown in Map 26, a large section of land in the Lower Rush subwatershed is in Ag/Forestal District.

10.6.8 Lower Rush Zoning

As shown in Map 27, the land area of the Lower Rush subwatershed is predominantly zoned Agricultural.  In Agricultural zone, one dwelling is permitted per 25 acres.  However, many smaller parcels predated the zoning ordinance and thus have higher density of dwellings.  About eight percent of the Lower Rush is zoned residential or commercial.  This is one of the three subwatersheds having the highest percentages of commercial and residential zoning in the County.

The County’s main General Commercial zone of 60 acres on Rte. 211 is in the northwestern part of the Lower Rush subwatershed.  There is also an area of a little less than 200 acres on the northeast part of the subwatershed that is zoned Rural Residential (5 acre parcels).

10.6.9 Future Development in Lower Rush Subwatershed

In the Lower Rush subwatershed, under current zoning and subdivision restrictions, approximately 110 new developable parcels could be subdivided from existing parcels in agricultural and residential zones.  In addition, there are about 90 existing parcels that do not have dwellings on them.  In combination, the construction of dwellings on existing parcels plus newly subdivided parcels could yield about 200 new dwellings.  At an average of 2.5 persons per dwelling, this would yield an additional 500 population beyond the current estimate of 300 residents, and a population density of about 180 persons per square mile. 

At present, there are on average about .16 miles of private road or driveway per developed parcel in the Lower Rush.  Development of 200 parcels would add about 32 miles of private road to the present 34 miles.  This would further fragment forests and compromise stream buffer areas, and contribute to sedimentation and erosion of streams.

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