Impact of Land Use on Ground Water Quality in the Grand Traverse Bay Region of Michigan1
- R. Rajagopal2
Investigations in townships surrounding the Grand Traverse Bay of Michigan show identifiable geographic relationship between ground water quality and land use. Wells averaging 32 m deep in thinly populated areas (cherry orchards) measured an average of 3.75 ppm nitrate-N, indicating the effect of prolonged years of fertilizer application. Wells averaging 19 m deep in predominantly residential areas had an average of 1.31 ppm nitrate-N, indicating possible contamination from septic tank effluents. An average of 0.18 ppm of ammonia-N was detected in marshy wetlands.
An analysis of temporal variations in ground water quality with reference to precipitation, streamflow, and a trend component provided high as well as low R2 (0.92 to 0.12; R2 = square of the multiple correlation coefficient) producing regression models, indicating the effect of site specific conditions. A year-long observation of a sample well (43 m deep) surrounded by cherry orchards had an average of 18.25 ppm nitrate-N in a range of 13.09 to 20.64 ppm, almost double the standard considered safe for human consumption. Ammonia-N and chloride measurements from a shallow well (12.5 m deep), surrounded by residential and commercial activities, showed synchronized variations over a year (correlation coefficient r = 0.75, significant at 1% level), suggesting the existence of a common source of contamination.
In summary, it is reiterated that the analysis of ground water quality problems require a different philosophical approach from those of water quantity and surface water quality modeling.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © . .