ASSESSMENT OF THE BROAD RUN WATERSHED,
CHESTER COUNTY, PENNSYLVANIA

This project is being done in cooperation with the Chester County Water Resources Authority and West Bradford Township.

NEED FOR THE PROJECT
The Broad Run Watershed is a 7-square mile watershed entirely contained within the boundaries of West Bradford Township, Chester County, Pennsylvania. Broad Run flows from its headwaters, just south of Thorndale, to the southeast through predominantly residential, forest, and meadow lands to its confluence with the West Branch Brandywine Creek about 1.2 miles south of Marshallton. Broad Run is an exceptional value waterway as designated by the Commonwealth of Pennsylvania and is in the Lower Brandywine Scenic River area.

In the late 1970's and 1980's West Bradford Township experienced dramatic population growth resulting, in part, from a development consisting of 450 houses constructed in the headwaters. Development activities have continued along the stream corridor and are projected to do so into the future at an increasing rate. While there has been some significant success in protecting the watershed, there has not been a coordinated approach to protecting the stream valley or identifying and correcting problems caused by the changing land use within the watershed. This developmental pressure has raised concerns of township residents and officials that continued uncoordinated growth will result in irreparable damage to this high quality and scenic watershed.

Local officials need an assessment of the current condition of the stream corridors within Broad Run Watershed to identify the location, magnitude, and cause of existing and potential impairment. These baseline data can be used as a comparative tool from which to gauge the impact of continued changes within the watershed. Local officials require the information this type of assessment would provide to assist them in developing a restoration and management plan for their watershed that does not compromise the form and function of stream corridors or water availability.

PROJECT OBJECTIVES

1. Characterize the existing channel morphology, instream habitat, riparian buffers, and associated uplands within the Broad Run Watershed. This assessment will provide baseline data for comparison of the impact of future development within the watershed.
   
2. Quantify the parameters of the hydrologic cycle in the Broad Run watershed on an annual basis (water budget or mass balance).
   

• Classify stream types for entire watershed using Rosgen level 1 methods.
  
• Complete basic visual assessment of the watershed utilizing portions of the US Department of Agriculture Stream Visual Assessment Protocol, USGS National Water Quality Assessment (NAWQA) Protocol, and(or) US Environmental Protection Agency rapid bio-assessment. This visual assessment will create a numerical rating that is valuable in prioritization of future study and(or) remedial action.
  
• Select two reaches of Broad Run and assess using Rosgen Level II methods that quantify the character of the stream reach. Level II sites will be selected in order to maximize diversity between the study reaches. Selection will be based on a combination of observed valley type (strongly related to geology in this watershed), observed land use (generally forest, wetland, or pasture in this watershed), and(or) observed stream type. Each site will include two cross sections with monuments.
  
• Determine and describe watershed characteristics that relate to runoff patterns within the Broad Run watershed via a Geographic Information System (GIS) spatial data set utilizing the following coverages: physiography, land use, roads and streams, and geology.
  

• Complete rapid bio-assessment of Broad Run and its tributaries throughout the watershed. The rapid bio-assessment evaluates the representative characteristics of the stream.
  
• As part of an existing Chester County Stream conditions biological and chemical monitoring network, select three sites within the Broad Run watershed and assess the biologic conditions. These sites should be located so as to best characterize the biologic diversity of the watershed. Biological samples are generally taken during periods of low flow and at approximately same time during each year.
  
• At the three sites listed above, water-quality samples will be taken and analyzed. Chemical analysis can identify specific contaminants if biologic diversity indicates a disproportionate number of robust species versus environmentally sensitive species.
  
• Create GIS coverage for biological sampling sites and data.
  

• Establish a monitoring well network with at least 4 wells that will be monitored by USGS personnel. The monitoring well network will be dispersed throughout the watershed and will be comprised of residential and(or) business wells either abandoned or in use as available.
  
• Locate and inventory all significant diversions where water is removed or added to the watershed and all significant surface-water impoundments that might affect storage factors.
  
• Install a continuous-record stream gage with a continuous-record rain gage that will be operated from approximately February of 2002 until May of 2004. A partial-record station will be installed on a major tributary that enters Broad Run below the continuous-record station. This partial-record station will be rated and will include both a staff plate and crest-stage gage as standard equipment. A correlation will be established between the streamflow measurements conducted on Broad Run and those conducted on its tributary.
  
• Precipitation will be determined by data from the continuous-record rain gage; however, due to the possibility of equipment failure, and the importance of this variable to the annual water mass-balance, 3-4 manual rain gages will be installed and operated by volunteer network throughout the watershed. Data from the manual rain network will serve as quality assurance for the continuous-record rain gage and, in the event of equipment failure, will be used in the annual water mass-balance equation.
  
• Create GIS coverage for all measurement sites and data.
  
• Determine the annual water mass-balance. The annual water mass-balance equation must be solved for the period of April 1st to March 31st of the following year.

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