Fecal coliform disappearance in a river impoundment

Abstract

Fecal coliform (FC) disappearance studies were conducted in Ford Lake during the summer of 1979. Ford Lake, an artificial impoundment at the lower end of the Huron River drainage basin below Ypsilanti, Michigan, receives all upstream flow (2072 km2 of drainage). During dry weather an overall daytime FC disappearance rate of 0.4 (h-1) (K base e) was measured using dye tracer for timed collection. assuming a first order equation of the Chick type. Sedimentation was demonstrated as important in the overall FC disappearance in the upper end of the lake. Rooftop studies showed light level to affect daytime disappearance. Two types of wet weather conditions were documented: (1) where a substantial increase in flow occurred due to an isolated upriver storm; and (2) as a result of two different storm events in the Ford Lake area itself. In both cases, Ford Lake was effective in substantially reducing the large FC contribution.