Nutrient and Fecal Microbe Contamination within the Otter Creek Watershed, Madison County, Kentucky
Environmental Health Science
The Otter Creek watershed exhibits dissolved nutrient (ammonium, NH4; nitrate, NO3; phosphate, PO4) and fecal microbe contamination that compromises its water quality. The watershed covers a substantial portion of Madison County and consists of Lake Reba, Dreaming Creek, and its east and west forks, all of which enter the trunk of Otter Creek before flowing into the Kentucky River. We collected 330 water samples on three occasions during summer 2014 to determine the extent and sources of contamination. Nutrients were measured using colorimetric methods, whereas Escherichia coli counts were determined using IDEXX materials.
We found highest nutrient concentrations immediately below discharge from the Otter Creek sewage treatment plant, which is a point source for nitrate (3.5 - 4.4 mg/L N-NO3) and phosphate (0.8 - 1.0 mg/L P-PO4), whereas background levels were ~0.4 mg/L N-NO3 and ~0.09 mg/L P-PO4. The highest values for nitrate-nitrogen and phosphorus-phosphate were 4.3 mg/L (station STP-d, May) and 0.9 mg/L (station STP-d, May), respectively. Measurable ammonium occurs only sporadically; only two stations exceeded background concentrations of 0 mg/L N-NH4 for June and July sampling; the highest observed value was 1.8 mg/L N-NH4 (station CC, June). 44% of samples exceeded EPA E. coli concentration standards for human contact (>575 cfu/100 mL) and are distributed throughout the watershed, displaying classic non-point-source pollution. High counts are associated with pastureland and the urban portion of Dreaming Creek, so we attribute fecal microbe sources to runoff from surrounding pasturelands supporting cattle and to leaky sewage pipes serving the city of Richmond.
Crockett, Nathaniel, W.S. Borowski, 2014. Nutrient and fecal microbe contamination within the Otter Creek watershed, Madison County, Kentucky. Kentucky Academy of Sciences meeting, November 2014.
Kentucky Academy of Science, 100th Annual Meeting, Lexington, KY