A Lake's Response to Its Environment

Green Lake in Seattle, Wash., was studied to find the causes underlying its heavy algae blooms and alleged condition of pollution so that its recreational potential might be realized. Data were obtained on urban runoff, lake shore runoff, subsurface inflow, algae populations, waterfowl, composition of sediments, effect of wind-induced currents on water quality, and requirements of competing recreational water uses. Water and nutrient budgets are presented. Nutrient additions sustain heavy algae blooms throughout most of the year, and little can be done to reduce these additions. Bacterial contamination is directly related to waterfowl populations. Changes in physical and chemical water quality are caused largely by algal growth and decay. Recommendations are given for the addition of low-nutrient city water for dilution purposes, for dredging, and for shoreline improvements. It is recommended that increased quantities of storm water not be added.