Columbia River
The Head Waters Low Tide
COLUMBIA RIVER
The Columbia River, fourth-largest by volume in North America (annual average of 192 million acre-feet at the mouth) begins at Columbia Lake in the Rocky Mountain Trench of southeastern British Columbia at about 2,656 feet above sea level. The geographic coordinates at the head of the lake are 50°13’ north latitude, 115°51 west longitude.
The river flows north for some 200 miles (322 kilometers) and then turns south and flows for about 270 miles (434 kilometers) before crossing the border into Washington at River Mile 749, that is, 749 miles (1,205 kilometers) inland from the Pacific Ocean. More precisely, according to the BC Freshwater Atlas, the Columbia River in British Columbia is 760.356 kilometers long (472.463 miles).
For its first approximately 150 miles (241 kilometers) in the United States, the Columbia forms the reservoir behind Grand Coulee Dam. The river then bends west, south and east through central Washington, turns south and then west, and forms the border between Oregon and Washington to the Pacific Ocean. The mouth of the river is about 10 miles (16 kilometers) west of Astoria, Oregon. The geographic coordinates at the mouth (near Cape Disappointment, Washington) are 124.09344 west longitude, 46.246922 north latitude (these are the coordinates the U.S. Army Corps of Engineers cites as River Mile Zero). The total length of the river is about 1,243 miles (about 2,000 kilometers). The drainage basin covers 259,000 square miles (670,810 square kilometers), approximately the size of France, drains portions of seven states and British Columbia, and covers three degrees of latitude and nine degrees of longitude
