how much of the colorado river reaches the ocean
Flows at the mouth of the river have steadily declined since the beginning of the 20th century, and in most years after 1960 the Colorado River has run dry before reaching the Pacific Ocean. Irrigation, industrial, and municipal diversions, evaporation from reservoirs, natural runoff, and likely climate change, have all contributed to this substantial reduction in flow, threatening the water supply for the future. For example, the Gila River -- formerly one of the Colorado's largest tributaries -- contributes little more than a trickle in most years due to use of its water by cities and farms in central Arizona. The average flow rate of the Colorado at the northernmost point of the Mexico -- United States border (NIB, or Northerly International Boundary) is about 2,060 cubic feet per second (58 m / s), 1.49 million acre feet (1.84 km) per year -- less than a tenth of the natural flow -- due to upstream water use. Below this point, the remaining flow is diverted to irrigate the Mexicali Valley, leaving a dry riverbed from Morelos Dam to the sea that is supplemented by intermittent flows of irrigation drainage water. There have been exceptions, however, namely in the early to mid-1980s, when the Colorado once again reached the sea during several consecutive years of record-breaking precipitation and snowmelt. In 1984, so much excess runoff occurred that some 16.5 million acre feet (20.4 km), or 22,860 cubic feet per second (647 m / s), poured into the sea.