The Magothy River encompasses all the waters of the Magothy River and its tributaries northwesterly of a line beginning at Mountain Point, at or near Lat. 39° 3.567' N., Long. 76° 25.983' W., then running 168° (True) to a point at the east side of the Little Magothy River, at or near Lat. 39° 2.783' N., Long. 76° 25.767' W.