Effects of South Shore Drainage Basins and Clay Erosion on the Physical and Chemical limnology of Western Lake Superior

Abstract

A chemical and geological investigation of Lake Superior waters and sediments is presented. The study area extends from Superior, Wisconsin to Amnicon Point, Wisconsin, a distance of eight miles. Sampling was enacted on lake waters from the shoreline out to a distance of one mile. This region of the lake receives extensive amounts of Pleistocene red clay due to erosion and is subject to discharge from bordering streams and from the Puluth-Superior harbor. Additional studies were made at a deep water site located five miles out from the shoreline of the study area. Water samples were obtained under conditions of varying turbilbity of the waters (varying amounts of suspended solids). The waters in the study area varied in amounts of suspended solids from 3 to 60 pm · as compared to 0.2 to 0.5 ppm found in the open waters of Lake Superior. Calcium, hardness, and alkalinity under specific conductance of the waters in the study area were higher when large amounts of suspend solids were present. Iron and total phosphate concentrations are high in the study area (with a difect correlation between the two parameters) as compared to open lake waters. The concentrations of iron and phosphate are particularly high in the early summer. Bottom sediment samples in the study area, indicate fine sands to predominate (0.25 to 0.125 in diameter), with the normal spread extending from coarse sand through the lower limits of very fine sand. In fact, no clearly established clay or mud bottom was recognized during the entirety of the field sampling session. The principal source of suspended clay is from drainage waters eroding red clay containing basins and from storm wave action along the Valders clay outcrops.