The theme: phosphate from the watersheds controls phosphate in Cayuga Lake which limits algal production in the summer as measured by chlorophyll. Important facts: a)The annual amount of water entering the lakes from all of the watersheds varies from 10 to 15 % of the lake volume because the lake is very large (deep). b) The lake “turns over”; that is, mixes during the winter so that concentration of dissolved solutes such as phosphate are the same north to south, top to bottom etc. C) The annual yearly inflow from the watersheds is episodic: running averages of three to 6 years in length are variable. The following variables are correlated with each other: (1)running averages over 6 years of inputs of stream phosphate (2) annual averages of phosphate in lake water deeper than 60 m 3) phosphate in surface lake water in early spring 4) average chlorophyll during summer.