Created on Thursday, 09 August 2007 07:04
Last Updated on Thursday, 09 August 2007 07:04
Water samples taken by Friends of the Mad River volunteers on Monday morning, August 6, showed favorable swimming conditions in the middle reaches of the Mad River from the Lareau swimhole to the Meadow Road Bridge, and also at Ward Access in Moretown.
Sites in Warren and in Moretown from the North Road downstream to the Ward Clapboard Mill were sampled after rain began to fall, and these sites were found to have high E. coli levels. This week's sampling results are a good illustration of how linked E. coli levels are to rainfall. Swimmers are highly encouraged to consider recent weather and upstream activities as factors that may affect water quality. A rainstorm that turns the Mad River's waters brown with sediment will probably increase E. coli levels significantly in many of the popular swimming areas.
The state water quality standard for recreational waters measures E. coli bacteria, an indicator of pollution from human or animal waste. Sixteen of 37 sampling sites tested were in violation of Vermont's water quality standard of 77 colonies per 100 milliliters of water. The bacterial pollution developed as water levels in the low river began to rise at approximately 8:15 a.m.
Flow readings at the USGS gage in Moretown (http://waterdata.usgs.gov/nwis/uv/?&site_no=04288000) increased from a low of 32 cubic feet per second (cfs) at 8 a.m. on August 6 to a high of 72 cfs recorded at 9:30 p.m. that same day. Some Mad River Watch samples were collected while the river flow was still low and declining (LD) and E. coli levels were low, while others were collected just after the river began to rise (LR).
With an increase in water flow like this, higher E. coli levels result as the land surface is "washed" and bacteria is flushed into the brooks and river. Water levels may rise over the weekend if forecasted storms amount to significant precipitation.
Water temperatures in the Mad River are still hospitable for brook trout, who can generally tolerate temperatures below 75 degrees. Above these temperatures trout will seek colder waters in the smaller tributaries.
For more information about E. coli and the Mad River Watch program or to report a river-related illness call Friends of the Mad River at 496-9127. Thanks to this week's Mad River Watch volunteers Kirstin and Eleanor Reilly, Kathryn and Pam Barnes, Patti and Cyril Greene-Swift, Katie Sullivan, Kinny Perot and Jay Meadows.