The Río Chagres is one of the longest and most vital of the approximately 150 rivers that flow into the Caribbean. Part of this river was dammed to create Gatun Lake, which forms a major part of the transit route between the locks near each end of the canal. Both Gatun Lake and Madden Lake (also filled with water from the Río Chagres) provide hydroelectricity to the former Canal Zone area. The Río Chepo, another major source of hydroelectric power, is one of the more than 300 rivers emptying into the Pacific.