<Tr> <Th> Discharge </Th> <Th> cfs </Th> <Td> 9,650 </Td> <Td> 9,740 </Td> <Td> 10,500 </Td> <Td> 16,000 </Td> <Td> 28,000 </Td> <Td> 32,800 </Td> <Td> 18,300 </Td> <Td> 13,200 </Td> <Td> 10,900 </Td> <Td> 9,530 </Td> <Td> 9,620 </Td> <Td> 9,440 </Td> </Tr> <Tr> <Th> m / s </Th> <Td> 273.3 </Td> <Td> 275.8 </Td> <Td> 297.3 </Td> <Td> 453.1 </Td> <Td> 792.9 </Td> <Td> 928.8 </Td> <Td> 518.2 </Td> <Td> 373.8 </Td> <Td> 308.7 </Td> <Td> 269.9 </Td> <Td> 272.4 </Td> <Td> 267.3 </Td> </Tr> <P> The United States Geological Survey (USGS) operates or has operated 46 stream gauges to measure the discharge of the Colorado River, ranging from the headwaters near Grand Lake to the Mexico--U.S. border . The tables at right list data associated with eight of these gauges . River flows as gauged at Lee's Ferry, Arizona, about halfway along the length of the Colorado and 16 miles (26 km) below Glen Canyon Dam, are used to determine water allocations in the Colorado River basin . The average discharge recorded there was approximately 14,800 cubic feet per second (420 m / s), 10.72 million acre feet (13.22 km) per year, from 1921 to 2010 . This figure has been heavily affected by upstream diversions and reservoir evaporation, especially after the completion of the Colorado River Storage Project in the 1970s . Prior to the completion of Glen Canyon Dam in 1964, the average discharge recorded between 1912 and 1962 was 17,850 cubic feet per second (505 m / s), 12.93 million acre feet (15.95 km) per year . </P> <P> The drainage basin or watershed of the Colorado River encompasses 246,000 square miles (640,000 km) of southwestern North America, making it the seventh largest on the continent . About 238,600 square miles (618,000 km), or 97 percent of the watershed, is in the United States . The river and its tributaries drain most of western Colorado and New Mexico, southwestern Wyoming, eastern and southern Utah, southeastern Nevada and California, and nearly all of Arizona . The areas drained within Baja California and Sonora are very small and do not contribute measurable runoff . Most of the basin is arid, defined by the Sonoran and Mojave deserts and the expanse of the Colorado Plateau, although significant expanses of forest are found in the Rocky Mountains; the Kaibab, Aquarius, and Markagunt plateaus in southern Utah and northern Arizona; the Mogollon Rim through central Arizona; and other smaller mountain ranges and sky islands . Elevations range from sea level at the Gulf of California to 14,321 feet (4,365 m) at the summit of Uncompahgre Peak in Colorado, with an average of 5,500 feet (1,700 m) across the entire basin . </P>

When did the colorado river stop reaching the ocean