ABSTRACT A computer model has been developed that simulates several water quality parameters in a stratified lake during the main growth season. The model is process oriented and simulates heat transfer, light penetration, mixing by wind and natural convection, inflow and outflow, settling of particles, and several biological and chemical processes related to primary productivity. In the simulation, the lake is subdivided into layers of variable thickness. The timestep of the simulation is one day. Input to the simulation includes weather parameters, lake morphometry and inflow rate, and quality. Output consists of daily vertical distribution of water temperature, dissolved oxygen, suspended solids, up to three forms of plytoplankton, and up to three forms of phosphorus. The model is designed as a management tool to test lake treatment alternatives in planning lake restoration projects. The structure of the model allows individual lake treatment submodels to be inserted into the model without changing the...