Contribution of a Forested Watershed to Fecal Contamination in Ranch Brook: A Water Quality Analysis
Escherichia coli , better known as E.coli, is a common fecal indicator. • Fecal indicators are used to predict the risk of human illness due to pathogens transmitted through fecal matter. • Fecal levels in stream are often strongly correlated with land development. • New research has begun to suggest that streams draining “natural” forested areas may also contain contamination levels that violate state and federal water quality standards.
Site Characteristics: • Ranch Brook watershed is 9.84 km³ • Composed primarily of undeveloped forestland. • Located on the eastern slope of Mt. Mansfield. • Drains into Lake Champlain • Ecosystem is a representative of the Northern Forest Ecosystem that is predominant across the entire Northeastern United States.
Water Quality Standards • U.S. EPA e.coli Standards 235 organisms / 100 mL • Vermont e.coli Standards : < 77 organisms/ 100 mL • Vermont has the • most stringent e.coli • standards in the U.S. • Incidentally, due to • Vermont’s tougher standards, • frequent beach closings and • violations that give the • impression of poor water • quality are relative. Ranch Brook Watershed Stream Network Model
Methods • Replicate 100 mL samples taken at the USGS stream gauging station each week. (August - October 2004) • Samples analyzed using IDEXX Colisure & Quanti-Tray 2000 - samples require prep and incubation within 6 hours - incubation period of 48 hours at a constant 35˚C - color indicator for fecal coliform - fluorescence indicator for e.coli (UV light)
Storm Sampling Methods • October 16th storm • Began Sampling at 4:00 AM • Replicate 100 mL samples taken hourly
Methods • Weekly Samples & One • Storm Sample • Weekly results are expected to show a concentration peak in • late summer, then a decline as temperature drops. • Storm results are expected to show high e.coli concentration due to high loading of organic material and extended period of no rainfall.
Weekly Sample Results • Results from weekly sampling support previous study results • Higher values in • August • Lower values as • Temperature drops
Storm Results • E.coli concentrations rose along with the hydrograph, • with the highest value corresponding with the storm’s peak • All storm samples violated VT Standards, while 2 of 7 • samples violated EPA Standards
Discussion Why is this important? Results indicate that “pristine” & “natural” watersheds can produce bacterial concentration levels that exceed both VT and EPA Water Quality Standards. Further research will help policy makers determine what level of standards will be most attainable and also help understand what is impacting water quality further downstream.
What Next? • Wildlife sources – moose & deer habitat • Beaver ponds? • Correlation with sediment loads? Stay Tuned……