The source of a large river system, for example, the Missouri
river, is often taken
as the location of the uppermost spring in the farthest tributary.
Fig. 2 Brower's Spring, in the
headwaters of Hell Roating Creek,
Fig. 3 Hell Roaring Creek, in southwestern Montana, the most upstream tributary of the Missouri river.
The Missouri River is the longest river in North America. With its source in the Rocky Mountains of western Montana, the Missouri flows first north, then east and south for 3,767 km (2,341 miles) before joining the Mississippi River north of St. Louis, Missouri. The river drains a sparsely populated, semiarid watershed of 1,370,000 square kilometers (529,200 square miles), which comprises parts of ten U.S. states and two Canadian provinces. Although nominally considered a tributary of the Mississippi, the Missouri River is much longer and carries a comparable volume of water. The combined Missouri-Mississippi forms the world's fourth longest river system in the world.
The longest tributary of the Missouri river
begins a short distance upstream of Brower's Spring,
on the southeastern slopes of Mount Jefferson,
in the Centennial Mountains of the Bitterroot Range
(click on top of Fig. 4 to
see red arrow in the large display). From there it flows first
as Hell Roaring Creek, then west into Red Rock Creek;
then it swings northeast to become the Beaverhead River;
and finally it joins the Big Hole to form the Jefferson river.
The latter joins the Madison river to become the Missouri River at
Missouri Headwaters State Park near
Fig. 4 Missouri river basin, indicating the location of Brower's Spring, in southwestern Montana,
The true source of the Missouri river is in the Rocky Mountains, on the
U.S. Continental Divide,
at
Fig. 5 Panoramic view of the true geographical source of the Missouri river.
Fig. 6 Panoramic view of the location of Brower's Spring.
The distance between the two points may be calculated using
the online calculator online_geodistance_two.
The result shows that the distance
is
Fig. 7 Distance between Brower's Spring and the true geographical source of the Missouri river.
The Lewis and Clark Expedition, which took place
between May 1804 and September 1806,
Fig. 8 Route of the Lewis and Clark expedition (red outbound; blue inbound).
The river portion of the expedition departed from Camp Dubois, Illinois, near
the present-day Wood river,
on May 14, 1804,
ascended
the Missouri river and
came close to its source in Montana, proceeding
instead
to the Pacific Ocean. On August 12, 1805, they
crossed the U.S. Continental Divide at Lemhi Pass and reached the Salmon river.
Finding the latter too risky
to navigate,
they decided instead to portage
onto the neighboring watershed
Fig. 9 Lewis and Clark on the Lower Columbia river.
Fig. 10 Lewis and Clark on the Lower Columbia river.
Fig. 11 Lewis and Clark at the mouth of the Columbia river. |
200317 14:35 (PDT) |
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