Issues in Our Watersheds
Watersheds are complex systems! What we measure in the streams is the end result of many factors occurring on the land. In this cause and effect environment, we need to identify issues on the land, and separately identify issues with what we measure in the streams. Only then can we begin the process of attributing issues in the streams to problems on land. This is an iterative process, and we must be cautious about attribution. GVWA is steadily learning more about what is occurring on the land as well as about what is happening in the streams–especially during stormwater events.
On Land Issues:
On Land Issues:Impervious Cover and Runoff
See GVWA’s mapping of impervious cover here
Legacy Sediments
Along with much of the Northeastern United States, Northern Chester County has a rich history of hydropower installations dating from the early 1700s. Mills and mill dams were built at over 60 sites in the French and Pickering Creeks and at most of these sites there are readily identifiable Legacy Sediment accumulations. This map shows the location and detail for each mill that was identified. LINK
Stream banks at these sites are often rapidly eroding vertical faces of sediments that are very likely delivering dis-proportionally large loads of sediments into the creeks. While this erosion is a relatively new topic in water quality studies, the high rates of erosion at these sites has been ongoing for many decades if not longer. Measuring erosion rates at these sites is useful, and this map series looks at some ways to make measurements.
In Stream Issues:
Sediments: Sediments clog the natural structure of the stream substrate and greatly reduce the natural function and habitat in the stream.
Bacteria: Bacteria and pathogens from many animal sources are washed into the streams, potentially rendering these waters unsafe for recreational use. Bacteria and pathogens also grow abundantly in stream sediments. GVWA is working on understanding how these two sources are working together to produce the fecal coliform levels we are observing.
Nutrients: Nitrates and phosphates from excess fertilizers and other sources which enter the stream have the potential to disrupt the natural food chain, causing accelerated growth of some plants, and harming others.
Organics: Stormwater runoff is often loaded with organic materials from lawns, fields, impervious surfaces, and other land based sources.
Pollutant laden runoff is “discharged” directly into our streams at thousands of places throughout the watershed, often with a volume much greater than the stream’s baseflow. The streams become essentially conduits for a type of waste water. The increased flows also damage the stream channels in many ways.
Stormwater is often a hidden problem, and the solutions are readily available. GVWA is actively bringing this issue to the public’s awareness, and we are advocates for broader implementation of
Legacy Sediments are also contributing to excessive sediments, bacteria, and nutrients in our streams.