In July, a team of volunteers and watershed assessment professionals netted samples of tiny swamp creatures from The Great Swamp, carefully peering at their finds. A 2012 study had turned up some surprises.
Countering the conventional wisdom that watersheds are passive accumulators of society’s wastes with pollutant levels progressively increasing downstream, the recent report released by Friends of the Great Swamp (FrOGS) showed water quality in the Swamp River improving as the water flowed north from Pawling to Dover Furnace Road.
“This surprising finding seems to be due to the living wetlands embracing the river,” said Dr. Jim Utter, Chairman of FrOGS. The study, based on biotic samples taken in July 2012 by Schenectady-based Watershed Assessment Associates (WAA) from four Swamp River sites and five tributaries, found the main artery of the Great Swamp’s North Flow is actually cleaned as it moves slowly through wetland plants and heads downstream.
WAA conducts biological stream assessments using aquatic benthic macro-invertebrate communities–in other words, they sample bottom-dwelling small animals including insects, snails, crustaceans and worms–using methods that have been standardized by the EPA and the NYS DEC. This approach to water quality assessment has been widely accepted as a useful, cost-effective technique, since the animal species at the bottom of streams are relatively sensitive to a wide range of environmental stressors, both physical and chemical. The differences between the species found in each sample and what biologists expect to find in a natural stream in the area indicate localized impacts on water quality and frequently provide insight into the type of impact.
Samples taken from the tributary streams in 2012 reflected the kinds and intensity of land use surrounding them. According to the EPA and DEC standards, three of the streams showed moderate impact on their water quality, while two rated ‘slight impact.’
Development pressure in the North Flow corridor of The Great Swamp prompted FrOGS to retain WAA in 2010 and again in 2012 to begin building a baseline of water quality information for the tributaries and two main rivers (the Swamp River and the East Branch Croton). Their goal is to produce a comprehensive water quality baseline of conditions throughout the watershed before further development occurs. According to Utter, having this data will make it possible to conduct trend analyses, evaluate point and non-point pollution sources, and assess impacts of development. It will be an invaluable resource for local Planning Boards and fill a glaring gap in the information available for regional planning decisions, he said.
“An important implication of this study is that we must protect the remaining wetlands in all of our watersheds,” said Utter, “but suggesting we can rely on them to clean all the pollutants we want to dispose into our streams is a very dangerous delusion. Pollution avoidance is the best, easiest, least expensive, and safest policy.”
Both WAA and FrOGS agree that a more comprehensive study needs to be conducted, encompassing more tributaries and giving a bigger picture of the health of the watershed. The natural wetland processes resulting in pollutant removal from stream water have limits, Utter explained. “We need to figure out what these limits are and recognize declines in wetland functions before we approach the limits so we don’t damage this valuable infrastructure.”
Last month, FrOGS assembled 13 volunteers who worked with the WAA team re-sampling the 2012 sites and six additional sites in the Great Swamp. These samples will be analyzed over the winter with results available next June. FrOGS’ goal is to characterize all of the waterways in the Great Swamp, but progress is limited by the cost of analyses, so a fund-raising effort is being mounted. Results of both the 2012 and the 2010 reports are can be viewed on the FrOGS website, frogs-ny.org.
The Great Swamp
WAA demonstrating stream sampling method
Samplers peer at benthic creatures