By Lauren McGrath Director of Watershed Protection Program, Anna Walsh, Conservation Data and
GIS Specialist and Sarah Barker, Watershed Program Technician
Aquatic ecosystems, like the headwaters of Ridley, Crum, and Darby Creeks studied in the State of Our Streams (S.O.S.) report, are facing a devastating reality: if human activity continues unchecked, it will result in the destruction of this invaluable resource. Studies around the world have shown that climate change and human development have had disproportionate impacts on aquatic systems, causing as high as an 85% decline of all aquatic habitat.1 As this ecosystem declines and species are lost, it becomes weaker in the face of future disturbances. At the state level, the Pennsylvania Department of Environmental Protection’s Integrated Water Quality Report published in 2024 shows that across Pennsylvania, 34% of stream miles are considered impaired for one or more uses, an increase over the 2022 report. More locally, 79% of stream miles in Chester County and 95% of stream miles in Delaware County are considered impaired.2
Since 2018, WCT’s Watershed Protection Program has monitored water quality at ten sites in the headwaters of Ridley, Crum, and Darby Creeks, visiting these sites once every four weeks to collect data. The goal of the program is to understand local trends in water quality and how water quality relates to land use. To provide a biological context to water quality data, we have also conducted surveys of stream insects, freshwater mussel, and diatoms. The updated S.O.S. report contains findings from all of this data, as well as data from the Darby and Cobbs Creek Community Science Program and observations of local wildlife.
In the study area covered in the 2025 edition of the S.O.S., Ridley, Crum, and Darby Creeks are considered impaired for their designated aquatic life uses, meaning water quality is not high enough to support the full diversity of fish and other organisms that should live in the stream. The data presented in the S.O.S. showcases the intricate relationship between activity on the landscape and the reaction of the waterway. From the compelling complexities of water chemistry, to the biology of stream insects and diatoms, similar patterns are emerging from the data: the region’s streams have warm waters, high chloride levels (from the application of road salt before winter storms), and elevated nutrients. However, there is a relationship between concentrated land protection and restoration efforts: where there is more development, water temperatures rise, as does the impact of road salt and nutrients. Where there is more protected open space and, importantly, more forest cover, these impacts are reduced (Figure 1).
Over the last seven years, Watershed Protection Program staff have witnessed the increasing instability of these systems first hand. Extreme flooding, like that of 2021’s Hurricane Ida, has caused substantial erosion and contamination. The historic drought of the fall of 2024, where no rain fell in the month of October, led to dangerously low flows and elevated chloride levels – an indication of salt build up in the soils and groundwater. It is difficult to overstate the impact that events like these have had on the wildlife that call this region home. Predictions are that climate change-driven instability will continue to be a significant hurdle for aquatic ecosystems to clear as we move into the future.
Alongside the observed realities of climate change, Watershed staff could have never predicted that we would document so many unexpected new wildlife species in these watersheds over the last seven years. Despite the combined pressures of human expansion and increasing climate instability, this region retains an incredible ability to recover and support sensitive and declining populations – from freshwater mussels, one of the most at risk groups of organisms on the planet, to the American river otter, which had been driven almost to extinction in Pennsylvania due to poor water quality.
Our hope is that this report will help community members throughout the region understand the science behind the stream research and offer tangible suggestions for ways to improve watershed health. We know that we can improve the health of our streams when we work together. Life depends on it.
References:
World Wide Fund for Nature. (2024). Living Planet Report 2024 [Online report]. WWF. Retrieved [July 15, 2025], from Living Planet Report website.
Pennsylvania Department of Environmental Protection. (2024). Pennsylvania integrated water quality report 2024 [Interactive report]. Commonwealth of Pennsylvania. Retrieved [July 15, 2025], from Pennsylvania DEP website.
Funding for the S.O.S. publication was awarded through the “Protect Your Drinking Water” grant program, administered by the Pennsylvania Environmental Council with funding from Aqua, an Essential Utilities Company.
