§ 168 — Prescriptive rights of drainage; application of Sec. 167

Section 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.