This report describes the physical, chemical, and aquatic-biological characteristics that could affect regional water quality in the Red River of the North study unit. These characteristics define the overall environmental setting of the study unit. This report provides base line and historical information for future reports that will address specific water-quality issues and processes controlling and affecting water quality in the study unit, and for reports for the national-synthesis component of the NAWQA program that will integrate the results of the study-unit investigations.