Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 111, § 168

The preceding section shall not destroy or impair rights acquired by legislative grant prior to July first, eighteen hundred and seventy-eight, or destroy or impair prescriptive rights of drainage or discharge to the extent to which they lawfully existed on that date; nor shall it be applicable to the Merrimack or Connecticut rivers, or to so much of the Concord river as lies within the limits of Lowell.