In Massachusetts, the Nashua River basin is located in Middlesex and Worcester Counties and includes all or part of 27 cities and towns, including Fitchburg, Leominster, and Worcester.

Altitudes range from 2,006 ft at Wachusett Mountain to about 155 ft above sea level where the Nashua River crosses into New Hampshire. Unless otherwise noted, the description of the water resources of the Nashua River basin is based on Hydrologic Investigations Atlas 276 (Brackley and Hansen, 1977).