Long Lake in Washington has become a popular recreational site and as a result an increasingly popular area for real estate development which has resulted in a large number of permanent and weekend homes along its shores. There have been complaints, particularly in the last ten years, about the deterioration of water quality in Long Lake. The objectives of the study were to critically examine Long Lake and its tributaries in terms of a dynamic system. Described is the trophic status, the nutrient levels, the source and cause of nutrient input, the nutrient budget, the salinity budget, the phytoplankton and zooplankton populations, and correlation of changes in zooplankton populations with changes in phytoplankton populations.