White Clay Creek Stream Watch Project

Summary

The White Clay Creek watershed, located in Chester County, Pennsylvania and New Castle County, Delaware, is a valuable source of drinking water and possesses outstanding scenic, wildlife, recreational and cultural value. It was the first watershed in its entirety (280 km2) to be designated as a National Wild and Scenic River.  The Stream Watch Program was initiated because of concerns of rapid land development taking place in the White Clay Creek (WCC) watershed. The goals of this study were to evaluate water quality in WCC and its tributaries using aquatic macroinvertebrates, and make data available to encourage efforts to improve and/or protect water quality in WCC.

Aquatic macroinvertebrates (insects and non-insects such as worms and mollusks) are a widely accepted tool in water quality monitoring programs. Macroinvertebrates were sampled at 18 sites located throughout the WCC watershed for the most part annually from 1991 to 2008. In addition, several sites in the Avondale area were sampled in 2005.

The macroinvertebrate data were used to calculate a Macroinvertebrate Aggregated Index for Streams (MAIS) that integrated various types of information into a single number that classified streams as Good, Fair, or Poor. Of the 18 long-term monitored sites, only one (Site 11) was classified as Good, 9 sites were Fair (Sites 12, 0, 3, 4, 7, 19, 17, 24, 23) and 8 sites were Poor (Sites 25, 18, 16, 6, 14, 20, 21, 22). The most upstream sites (Sites 11, 0, 19) scored higher than sites downstream on the same branches. All three branches of the upper White Clay had sites in the Fair and/or Poor category and all sites on the Lower Mainstem were Poor indicating degraded water or habitat quality. PA DEP and DNREC also consider water quality in WCC as impaired (based on their 303 (d) list).

Map of sites sampled in the White Clay Creek watershed from 1991-2008. Stream condition was rated using benthic macroinvertebrates, which are a widely accepted tool in water-quality monitoring programs.

The exact cause(s) of degradation at various locations in WCC are not known, but often stream degradation can be linked to the human uses of water and land. Land use is variable in the watershed but mainly rural (agriculture) in PA and mostly suburbanized (homes and industry) in DE. As the watershed becomes larger (moving downstream) water conditions become more degraded corresponding to an increase in impervious surfaces (parking lots and roads), and developed areas (buildings). It is important to recognize that water conditions are Poor in the Upper Branches in PA before it ever reaches the Lower Mainstem. Therefore, Poor conditions in the lower half of WCC should not be attributed solely to local land use changes or an increase in population density. Data from sites in the East, West and Middle Branches showed that as the number of people and the amount of developed land in the watershed increased the water quality decreased.

Sites on the East Branch suggest that water quality degrades in the vicinity of Avondale. Land use changes and point source discharges that occur in this area include the increased population density of the borough, a golf course, the wastewater treatment plant, and other non-point sources (e.g., residential areas and agriculture, including mushroom facilities). The East Branch remains poor south of Avondale and even with the addition of the West and Middle Branches, which were mainly rated as Fair, the main channel remains Poor. The large forested areas in the state parks in PA and DE also do little to improve the water quality of the Lower Mainstem through Delaware. Apparently in this case, large forests do not correct stream degradation that begins upstream.  Further studies may want to ascertain the specific influences that are negatively impacting the East Branch and propose suggestions for their remediation or prevention.

Compared to 150 sites in the nearby Schuylkill River basin the WCC watershed has fewer Good sites and more Poor sites. The lower water quality in the WCC compared to the Schuylkill watershed appears to be related in part, to the lower amounts of forest and higher amounts of agriculture in WCC watershed. Compared to long-term data (1972-2009) for exceptional value or high quality streams in the Schuylkill watershed, water quality in the upper WCC watershed was lower than some creeks (French and Pickering), but comparable to others (Valley). Within each site water quality varied over time, but there were no trends in our data or data from four USGS sites indicating conditions have improved or become more degraded from 1994 to 2009; although, the USGS sites showed that water quality has markedly improved since 1972.

Download the Stream Watch report.