The purposes of this study were to identify and discuss the major water quality problems in the Trinity River and to develop a mathematical model capable of representing present and future dissolved oxygen conditions in the river. The major study area included the West Fork and main stem of the Trinity River upstream of Lake Livingston. A preliminary model for the river below Lake Livingston was also developed and an initial investigation of eutrophication potential was undertaken for the headwaters of Lake Livingston. The aim of this investigation was to provide information for the planning of future treatment facilities and to suggest areas for future data collection and analysis.