Using the most recent hydrologic and water quality data issued by U.S. Geological Survey, this paper deals with the pollution of the lower Mississippi River for the 1978-1981 water years and compares the water pollution of this period with that of the 1973-1977 water years. The water quality of the lower Mississippi River has not been evaluated comprehensively.This paper utilizes the Cartesian coordinates approach in an appraisal of water quality of the Mississippi River for the first time. Thus, it provides a foundation for the further comprehensive evaluation of environmental quality and research of water resources. Using the most recent hydrologic and water quality data issued by US Geological Survey, this paper deals with the pollution of the lower Mississippi River for the 1978-1981 water years and comparable the water pollution of this period with that of the 1973-1977 water years . The water quality of the lower Mississippi River has not been evaluated comprehensively. This paper utilizes the Cartesian coordinates approach in an appraisal of water quality of the Mississippi River for the first time. Thus, it provides a foundation for the further comprehensive evaluation of environmental quality and research of water resources.