sentences:  The Westfield River is the Connecticut River's longest tributary in Massachusetts, although the Chicopee River's basin is much larger, and contributes more water to the Connecticut.The Connecticut's northern tributary, the Deerfield River, is nearly as long as the Westfield—only shorter than the Westfield.During the mid-20th century, the Westfield River was so polluted that it would change color based on the nature of the contaminant.