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The Sheepscot River Turbidity Pilot Study, - page 8 / 12





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to the spring and autumn storm events, even though the river discharge was much higher in June (more than 2.5 times the flow of the spring or autumn storms).  On the West Branch there are nutrient sources in the middle river between Palermo and Weeks Mills and between Weeks Mills and the Howe Road.  Choat Brook is one of those sources.  Turbidity is first obvious at Windsor Station and it intensifies by the time it reaches the Howe Road.  On the mainstem of the Sheepscot River, TN increases a little at Coopers Mills, but turbidity is not evident until Kings Mills and becomes slightly worse by Alna.

Figure 2.  June TP and water clarity results at Kings Mills relative to river discharge measured at North Whitefield.  A water clarity reading of 120 cm is the maximum possible with the turbidity tube (this means the clarity was actually greater than 120 cm).  The other sites had a similar pattern, and so are not illustrated.

The mean TN value for all of our samples is 0.37 mg/L and the average for the three baseflow samples is 0.43 mg/L.  In our earlier study (Whiting 2006) we found that the Sheepscot River was enriched with nitrate in comparison with the Ducktrap River (the averages were 0.28 and 0.09 mg/L respectively).  Without actual TN data, we had to assume (based on data from other rivers) that nitrate might be about one-half the TN value.  From this, we guessed that our samples were moderately enriched nitrogen in comparison with published regional means (EPA 2001, Smith et al 2003).  In the present study, with an average measured TN of 0.43 for baseflow samples, our findings are slightly enriched in comparison to Smith et al, but possibly not enriched or very slightly enriched for the EPA study (the regional means were 0.25 and 0.38 mg/L respectively).  Our guess that nitrate would be about one-half the TN value is a little off (it appears to be more like 65% of the TN value).  Our baseflow TP average was 20 mg/L for this study.  

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