In Massachusetts, the Blackstone River basin is located in Worcester County and small sections of Middlesex, Norfolk, and Bristol Counties, and contains all or part of 30 cities and towns, including the city of Worcester.

The terrain is characterized by gently rolling hills whose altitudes increase to the West. Elevations range from almost 1,400 ft above sea level near Worcester to about 150 ft at the border with Rhode Island. The description of the water resources of the Blackstone River basin is based on Hydrologic Investigations Atlas 682 (Walker and Krejmas, 1986).