State of Our Watersheds Report By Dr. Ralph Heister Jr., and Emily B. Geer edited by Pam Baxter March, 2001 A stream is a barometer of change in a watershed. When precipitation falls, it either evaporates from the soil, is incorporated into the groundwater, or it runs off into streams, carrying pollutants with it. If the precipitation is heavy enough, especially with an increase in paving and other impervious surfaces, the runoff may also cause stream flooding. By monitoring stream water quality and quantity, we can monitor the impact of changes within a watershed. This is the inaugural issue of the Green Valleys Association “State of Our Watersheds” report, covering the five watersheds in eastern and northern Chester County: Valley Creek, Pickering Creek, French Creek, Pigeon Creek and Stony Run. These watersheds are of such high quality that the Pennsylvania Department of Environmental Protection designated them for Special Protection. Together they encompass an area of 158 square miles. The purpose of this and subsequent annual watershed reports is to document the present condition of these five streams and watersheds, and how they are changing over time under the pressure of development. We will call attention to the major land use issues in each watershed that impact the stream water quality and quantity. Sustainable Watershed Management As a region, we in northern and eastern Chester County are almost entirely dependent on groundwater for our water supply. Therefore, it is important to know how much water we have and where it is, and to husband it as a precious resource. From 1995 to 1998, Green Valleys Association (GVA) developed a program that, if followed, will enable residents within the watershed area to live within present water resources. The program calls for the reduction of runoff by infiltrating stormwater to the maximum extent possible. It also calls for wastewater to be recycled by land application, i.e., not discharged directly into streams. This program is known as Sustainable Watershed Management, and it has been met with broad support. Many of the townships within the watersheds of Pigeon Creek, Stony Run and French Creek have recently passed—or are developing—ordinances that will protect their water resources in order to sustain their streams and groundwater, and that will sustain development as well. Stream Flows – Stream Health For each of the streams in our five-watershed area, this report includes a brief survey of the biological stream health, major land use issues within the watershed affecting stream quality and quantity, and the overall present condition of the stream. Where the U.S. Geological Survey (USGS) has a continuous recording gauge (at Valley Creek and French Creek), this report also includes stream flows for 1999. The data on stream health are from the Chester County—USGS biological diversity— monitoring program. The Hilsonhoff Biotic Index (HBI), shown in Table 1, is based on pollution tolerance of stream macro-invertebrates. The lower the index value, the higher the water quality. Table 1. The Hilsonhoff Biotic Index scale is used to interpret organic pollution data for our five streams. HBI WATER QUALITY DEGREE OF ORGANIC POLLUTION 0.00 - 3.50 Excellent No apparent organic pollution 3.51 - 4.50 Very Good Possible slight organic pollution 4.51 - 5.50 Good Some organic pollution 5.51 - 6.50 Fair Fairly significant organic pollution 6.51 - 7.50 Fairly Poor Significant organic pollution 7.51 - 8.50 Poor Very Significant organic pollution 8.51 - 10.50 Very Poor Severe organic pollution Note: There is a lag from data collection to data availability by the USGS. Therefore the most recent available data are used in this report.

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