After diversion of sewage effluent from Lake Washington, winter concentrations of phosphate and nitrate decreased at different rates. From 1963 to 1969, phosphate decreased to 28 percent of the 1963 concentration, but nitrate remained at more than 80 percent of the 1963 value. Free carbon dioxide and alkalinity remained relatively high. The amount of phytoplanktonic chlorophyll in the summer wa...