DIEL TURBIDITY CYCLES IN THE UPPER KALAMAZOO WATERSHED, SOUTH CENTRAL MICHIGAN

Diel cycles in turbidity and other stream parameters occur in the North Branch of the Upper Kalamazoo River. Although turbidity is an important water quality parameter, diel fluctuations are not accounted for in stream assessments. Data were collected at select sites in the stream and adjacent wetland areas between May and November, 2010. Turbidity, specific conductance, pH, ORP, and temperature levels were measured at 15 minute intervals using YSI datalogging sondes, and stage level and water table levels were measured at the same intervals using Levelogger pressure transducers corrected for barometric pressure. Cycles in turbidity typically peaked at ~7 NTU at approximately 4:00 AM, and range ~ 5 NTU, but during storm events, turbidity levels reached over 25 NTU. Water table levels also showed cycling, with a peak right before sunrise, and a trough right before sunset, changing approximately 30 cm over a course of 24 hours, which is likely the effect of wetland pumping. Stream stage levels did not show definite cycling like water table levels, but showed some change in stage that could be attributed to groundwater input.

Previous student research on the nearby Rice Creek Watershed showed similar relationships between turbidity and adjacent groundwater levels. The turbidity cycles were attributed to a wetland groundwater pumping phenomenon that resulted in baseflow, stream level, and turbidity cycling. Separate research conducted on the Clear Creek watershed in Iowa has suggested that turbidity cycling is caused by nocturnal bioturbidation. In both of these instances, the amplitudes of the turbidity cycles observed were considerably larger than those recorded in this study. Future work in the Upper Kalamazoo Watershed will focus on determining causes of diel cycling.