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Columbia River Facts
The Columbia River basin comprises some 260,000 square miles, from its
headwaters in British Columbia, Canada, to its mouth at Astoria, Ore.,
bordering Washington and Oregon.
The basin includes parts of seven states, 13 federally recognized
Indian reservations, and one Canadian province. Nineteen percent of the
watershed is in Washington.
The average annual flow for the Columbia River at The Dalles, Oregon
is approximately 190,000 cubic feet per second (cfs) (1 cfs = 448.8
gallons per minute).
The river’s annual discharge rate fluctuates with precipitation and
ranges from 120,000 cfs in a low water year to 260,000 cfs in a high
After dams were constructed along the river for flood control and
power production, the flow regime of the river changed. Records kept
since 1878 show that flows were much higher in the spring and lower in
winter before dam construction. In addition, the velocity of the water
moving down the river was significantly greater before dam construction
began in the 1930s.In 1917, Washington adopted a water code to help
manage water allocations from surface water bodies in the state,
including the Columbia River.
Since the water code was adopted, the state has allocated 768 surface
water and 1,379 groundwater rights on the mainstem Columbia River.
These Columbia River water users have the right to take approximately
13,000 cfs in instantaneous withdrawals from April through October, when
most crops are grown in the basin.
The total annual withdrawal from the mainstem Columbia River during
the growing season is about 4.7 million-acre feet of water. (1 acre-foot
= 325,851 gallons, enough water to cover a single square acre of land 12
The Bureau of Reclamation is the single largest water user on the
Columbia River mainstem and is allocated about two-thirds of the water
from the river. In Washington, the Department of Ecology is considering
87 new water-right requests to take an additional 1,650 cfs of water
from the mainstem Columbia River.
Pending applications for new water withdrawals located within
Washington State for the mainstem of the Columbia River total
approximately 1,650 cfs (87 applications as of September, 2002).
Columbia River Hydrology
The following attachment provides information about the hydrology of the
Columbia River. This information has been shared with the National Academy
Columbia River Basin Maps
The following maps provide an overview of current information about the Columbia
River Basin: (Due to the level of detail on these maps, and the need to
maintain a high quality, viewable and printable maps, some of the files are very
Columbia River Photos