Margaret Reuss, wife of Rep. Henry S. Reuss (D-Wis.), was one of five persons rescued yesterday from the fast-flowing, rain-swollen Potomac River after two boating accidents.

No serious injuries were reported in either of the incidents, both of which occurred north of the District line. However, a woman who had been in a canoe with Mrs. Reuss when it tipped over was treated for exposure at Suburban Hospital.

Mrs. Reuss was one of four persons in the canoe, which reportedly tipped after suddenly being swung broadside to a current about 1:30 p.m. at a point in the river that is near Lock 8 on the C&O canal.

Mrs. Reuss and the other woman, identified as Lucy Galbraith, were passengers in the canoe being paddled by one of the Reuss' sons, Christopher, of Arlington, and Robert Ebel, of the District.

The two men, both soaked, reached an island, not far from shore, to which they had been paddling.

Mrs. Reuss, according to the Cabin John volunteer fire department, grasped some branches that extended out 15 or 20 feet from the river bank, and clung to them.

Galbraith clutched a tree stump that rose above the churning surface of the mudbrown water.

Galbraith was partly immersed in the chill waters, and a U.S. Park Police helicopter that hovered overhead as part of the rescue effort "told us to hurry up," said Mike Close, of the Cabin John department.

When Close and other rescuers arriveed in two motorboats, Galbraith was already numb.

"The water was so cold," Close said, ". . . she couldn't have lasted much longer."

Galbraith was released later yesterday from Suburban after treatment in the emergency room.

About seven hours after Mrs. Reuss and the others were brought to safety, a 52-year-old man was spilled into the water when his kayak capsized in the Potomac near Old Angler's Inn.

The man, identified only as Kurt Patrick, of Michigan, was taken from an island by members of the Cabin John department.