Streamwatch Project

Summary

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.

Macroinvertebrates were sampled for the most part annually from 1991 to 2008 at 18 sites located throughout the White Clay Creek watershed. In addition, 6 other sites in the Avondale area were sampled in 2005. The macroinvertebrate data was used to calculate a Macroinvertebrate Aggregated Index for Streams (MAIS) that integrated various types of information into a single number that can be used to classify streams. Of the 18 long-term monitored sites, only one (Site 11) was rated as having Good water quality, 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). All headwater sites (Sites 11, 0, 19) rated higher water quality than downstream locations. 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 quality in the White Clay Creek watershed. Within each site water quality varied over time but there were no trends indicating sites were improving or becoming more degraded since 1991 when the study started. Compared to 19 sites in the nearby Schuylkill watershed the WCC watershed had more Poor sites (44% vs. 26%) and fewer Fair sites (50% vs. 63%). Move cursor over map to see an enlarged view with caption.

Average MAIS scores based on 1-12 years of data taken between 1994-2008. MAIS scores are used to classify streams on a continuum from Good (macroinvertebrate assemblages characteristic of clean, healthy streams) to Fair (experiencing moderate environmental stress) to Poor (experiencing severe environmental stress).

The exact cause(s) of degradation at various locations in White Clay Creek 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 Pennsylvania and mostly suburbanized (homes and industry) in Delaware. As the watershed becomes larger water conditions become more degraded (a decrease in MAIS score) corresponding to an increase in impervious surfaces (parking lots and roads), and developed areas (buildings). Although it is important to realize water quality is Poor in the upper three branches (at Sites 6 and 16) before it ever reaches the Lower Mainstem (Site 14), so Poor conditions in the lower half of WCC should not be attributed solely to changes in land use. Using sites in the upper three branches we showed that as the number of people or the % developed land in the watershed increased the water quality (as measured by MAIS) decreased. Sites on the East suggest that water quality becomes precipitously degraded in Avondale and may be attributed in part to the sewage treatment plant, mushroom industry, and non-point sources (i.e., agriculture). The East Branch remains poor south of Avondale even with the addition of the West and Middle Branches, which were mainly rated as Fair. The large forested areas in the state parks in Pennsylvania and Delaware also do little to improve the water quality of the Lower Mainstem through Delaware. Further studies may want to ascertain the specific influences that are negatively impacting the East Branch and propose suggestions for their remediation or prevention. Move cursor over graph to see an enlarged view with caption.