Is the Osage River the largest tributary of the Missouri River?

March 29, 2010 10:15 AM

Does the Osage River contribute the largest volume of water of all the tributaries of the Missouri River?
posted by clockworkjoe to Science & Nature (5 answers total)

This site claims the Yellowstone river is the largest tributary of the Missouri (scroll down to "Description of the Study Area"), as does this one (scroll down to "Warm Water"). And this site calls the Osage the "largest tributary of the Missouri River within the state of Missouri," which they probably wouldn't have qualified if they thought it was the largest overall.
posted by brainmouse at 10:28 AM on March 29, 2010

From the 2000 U.S. Census, this table appears to put the Platte at number one among Missouri tributaries, with a discharge of 990,000 cubic feet per second. The Yellowstone ranks lower, at 692,000.
posted by cirripede at 10:45 AM on March 29, 2010

cirripede: those numbers appear to be from the "length" column, not the discharge column.
posted by brainmouse at 10:55 AM on March 29, 2010

Right you are, brainmouse. Stupid error on my part, and I should have known, having lived much of my life along the mile-wide-but-six-inches-deep Platte. Score one for the mighty Yellowstone. In penance, I offer up Stan Howe's song Take Me Back Along the Yellowstone.
posted by cirripede at 11:07 AM on March 29, 2010

Best answer: The River Discharge Database (which collects USGS data) shows a mean annual flow rate of 360.31 m³/s for the Yellowstone (1911-1931, 1934-1995) and 295.74 m³/s for the Osage (1932-1992). (Both measured at the nearest point to the rivers' mouths on the Missouri I could find a monitoring station for with a decent number of years worth of data. Several miles away in both cases, but there don't appear to be any additional large contributions to either between the cited stations and the mouths as far as I can tell.)

However, also note the standard deviations are fairly high (98.78 m³/s and 162.98 m³/s, respectively). Of the 59 years for which their is data for both on those tables (1934-1992), The annual flow of the Osage was greater than that of the Yellowstone in 22 of those years, including 8 of the last 10.
posted by DevilsAdvocate at 11:42 AM on March 29, 2010