Sampling after a Storm
By: Corrie (friendv3) 2015.07.28
Sampling results from the fourth round of Friends of the Mad River’s 2015 Mad River Watch (MRW) volunteer water quality program show four sites with unfavorable swimming conditions Monday morning. Localized thunderstorms and intense downpours hit the watershed overnight Sunday, washing sediments and pollutants from the land into the river and streams. By the time of sampling Monday morning, tributaries seem to have cleared while several Main Stem sites tested above DOH/EPA safe E. coli level of 235 colonies per 100 mL of water.
The flow condition of the Mad River at the time of sampling Monday morning was high and declining (HD), measuring approximately 333 cubic feet per second (cfs) at the USGS flow gage in Moretown, down from about 495 cfs just 3 hours prior, after a night of intense, but geographically specific, thunderstorms and rain. The median flow for this date is 86 cfs.
Samplers also noted that, in general, tributaries had clear water while the Main Stem was very turbid, with many sediments suspended in the water. What do you think can explain this observation? Were headwaters not as affected by localized storms? Had the tributaries been more turbid earlier in the morning, but cleared by the time of sampling? Are headwater streams eroding less or contributing less sediment than the Main Stem?
Always remember that rains can cause E. coli levels to fluctuate, even on a daily basis, as water carrying pathogens moves down the watershed. FMR’s E. coli sampling results are intended to give you a sense of the conditions that lead to high pathogen levels in the water so you can be informed. You are your best protector - use common sense and don't swim for at least a full day after a rain.
E. coli is a type of coliform bacteria and is used as an indicator of pollution from human or animal waste and the potential presence of disease causing organisms. It is estimated that at the level of 235 colonies E.coli per 100 mL water, approximately 8 out of every 1,000 swimmers are likely to contract a water borne illness related to fecal contamination.
Many thanks to this week’s Mad River Watch volunteers: Paula & Charlie Baldwin, Susy Deane, Chase Fortier, Annie Macmillan, Fran & Gary Plewak, and Michael Ware. Thanks to Susanne and George Schaefer who drove water samples to the DEC’s lab in Burlington for phosphorus and turbidity analysis, to Sally Boudreau for posting data at ten swimholes across the watershed, and to Maryellen Kinhan for completing the Wait House E. coli lab analysis. The Mad River Watch Program would not be possible without these dedicated volunteers!
For more information about E. coli and the Mad River Watch program, click here. To view the most recent data report, click here. Results are also available on Facebook (“Friends of the Mad River”) and on sign posts at swimholes across the Valley. Friends is a community-supported organization, and depends on the generous contributions of its members to continue the Mad River Watch and other important programs; learn how to become a member and donate securely here.