NON-UNIFORM GROUNDWATER AND NUTRIENT INPUT IN THE UPPER KALAMAZOO RIVER, MICHIGAN
In addition to detailed temperature mapping, reconnaissance mapping along a 9 km reach shows numerous springs in the riverbed and along its banks. The largest measured spring has a flow rate of 6.5x10-3 m3/sec. Many of these are expressed geomorphically as small reentrants, presumably caused by basal sapping. These reentrants are visible on high resolution Google Earth imagery but do not appear on topographic quadrangles. There does not appear to be a simple correlation between sediment type and location of springs. Cold areas show slight clustering in approximately 100 to 400 m sections but still show considerable variability in location.
This, and previous studies, show that this reach of the Kalamazoo River has nitrate levels of 2-6 ppm. In contrast, springs contain relatively high nitrate, 11-20 ppm. Many, but not all, areas with cold sediment have similarly high concentrations in pore water. Pore waters in warm sediment and surface runoff from adjacent wetlands have uniformly low, less than 1 ppm, nitrate levels. The upper portion of the aquifer is reported to be contaminated with nitrate. Where this water passes through organic-rich wetland and riverbed sediments, nitrate is reduced and removed. In areas of focused flow, the nitrate is not reduced and is carried into the stream. A simple mass balance calculation suggests that at least a quarter of the base flow in the river bypasses the reducing sediment.