Pts. 1-2. North Atlantic Slope basins and south Atlantic Slope and eastern Gulf of Mexico basins.--Pts. 3-4. Ohio River basin and St. Lawrence River basin.--Pts. 5-6. Hudson Bay and upper Mississippi River basins and Missouri River basin.--Pts. 7-8. Lower Mississippi River basin and western Gulf of Mexico basins.--Pts. 9-14. Colorado River basin to Pacific Slope basins in Oregon and lower Columbia River basin