Chemical Data

Statistical covariance analysis of data collected by the Soap and Detergent Association during its Wisconsin Lakes Study assessed the effectiveness of an interim detergent phosphorus ban. The covariance of basic limnological parameters between lakes expected to be impacted by a detergent phosphorus ban and lakes not impacted by the ban was examined. A statistically significant change in either total phosphorus or chlorophyll-a concentrations associated with the imposition of the ban was not observed on any of the lakes studied. An increase in secchi depth temporally associated with the ban was noted on two of the study lakes. For these two lakes, however, this change is unlikely to have resulted from imposition of the ban since statistically significant changes in chlorophyll-a were not observed. The covariate analysis also quantified the degree to which temporal fluctuations in total phosphorus, chlorophyll-a and secchi depth measurements may be observed between geographically proximate lakes. INTRODUCTION A previous paper (Clifford, et. al., 1985) has described the Wisconsin Lakes study conducted by the Soap and Detergent Association. Six lakes which were expected to receive a significant percentage of their phosphorus loadings from wastewater treatment plant effluent/ along with lake one expected to receive effluent from domestic wastewater treatment systems, were monitored from 1978 through 1983. These lakes were considered as "test" lakes in guaging the effectiveness of the detergent phosphorus ban. In addition, monitoring was conducted upon three lakes not impacted by wastewater effluent. These lakes represented "reference" points from which water quality data would be unaffected by intervention of the ban. Lakes were grouped into test-reference pairs based upon geographic proximity.