This hydrologic atlas represents a part of a comprehensive study of the water resources of southeastern Michigan. The purpose of the atlas is to present data on (1) the physical features of the Belle River and its tributaries, (2) the characteristics of streamflow, (3) the quality of ground and surface waters, and (4) an evaluation of the ground-water potential of the area. The atlas is one in a series of atlases on several river basins in southeastern Michigan.