As previously noted, the St. Mary's River watershed is
located in the southern part of St. Mary's County along the
western shore of the Chesapeake Bay, within a sub-watershed
of the Potomac River (Fig. 1). It is the largest watershed in St.
Mary's County covering approximately 47,000 acres or about
73 square miles (about 15 miles in length by 5miles wide). The
watershed encompasses approximately one hundred miles of
freshwater streams and approximately eight miles of tidally
influenced river. The water quality throughout the watershed
varies, with greater amounts of non-point pollution entering
from the northern end in proximity of the largest town,
Lexington Park. The southern portion of the watershed
consists of primarily rural, farmlands and forests (Fig. 1).