McCoy, Elizabeth (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume LXII (1974)
Sonzogni, William C.; Lee, G. Fred
Nutrient sources for Lake Mendota- 1972, pp. 133-164 PDF (11.1 MB)
NUTRIENT SOURCES FOR LAKE MENDOTA—1 972 133 William C. Sonzogni University Wisconsin— Madison and G. Fred Lee University Texas— Dallas INTRODUCTION It has been several years since Lee et al. (1966) published an estimation of nutrient loadings to Lake Mendota (the paper was revised in 1969, but only with regard to. the figure for the annual nutrien't input from nitrogen fixation). Since that time new data and information concerning certain nutrient sources has become available. In addition, changes in the population and land use of the watershed have occurred. In view of the recent diversion of sewage effluent which normally entered tributaries to the lake, it is imperative that the sources, amounts and types of nutrients be estimated as well as possible, if the effect of this diversion is to be properly evaluated. It is the purpose of this paper to update the estimation of the total amounts of nutrients entering Lake Mendota as well as to provide some quantitative information on the forms of nutrients annually entering the lake from different sources. LAKE CHARACTERISTICS Lake Mendota, perhaps the most studied lake in the world, is the largest of the Madison lakes, which form a chain along the Yahara River. Formed as a result of moranic damming during the most recent ice age, it is classified as a hard-water, eutrophic lake according to most standards. The drainage area of Lake Mendota is composed mostly of fertile farm land and urban area. The hypohimnetic waters become devoid of oxygen during summer stratification and during late winter oxygen depletion occurs in the bottom water. Excessive weed growth and periodic algal blooms create offensive conditions during the summer months. The lake is located in south-central Wisconsin, which has a semi-humid climate. The monthly average temperatures range between 19 F and 73 F (Dane County Planning Commission, 1971). Precipitation averages about 30 inches each year, while evaporation amounts to about 24 inches a year.