The report documents a mathematical model developed to predict the steady state dissolved oxygen concentrations in streams and canals resulting from a specified set of streamflow, wasteload, and temperature conditions. The model will determine the streamflow required to maintain a specified dissolved oxygen goal and will search the system for available storage to achieve the goal. The model can be used to estimate mean monthly dissolved oxygen levels over a full year. Both carbonaceous and nitrogenous oxygen demands are included and up to five degrees of treatment for both can be specified. (Author)