FLOOD04610

• County: Statewide
• Basin: Statewide
• Title: Overview of River-Floodplain Ecology in the Upper Mississippi River Basin
• Date: 12/9/1996
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

52

OVERVIEW OF RIVER-FLOODPLAIN ECOLOGY IN THE UPPER MISSISSIPPI RIVER BASIN

- _ Canada
--
Unit;; Stat;;- - -

Fort Peck (Fort Peck Dam) (RK 2,651)

Sakakawea (Garrison Dam) (RK 2,237)

Oahe (Oahe Dam) (RK 1,725)

Sharpe (Big Bend Dam) IRK 1,566)

Francis Case (Fort Randall Dam)
IRK 1,416)

Yankton (RK 1,295)

Lewis and Clark (Gayins Point Dam)
RK 1,305)

Figure 5-3. Missouri River basin showing most of the civil works projects completed by the U.S. Army Corps of Engineers and
U.S. Bureau of Reclamation. RK, river kilometer (source: Hesse and others, 1989a).

Figure 5-4. Mean (solid line), maximum (doned line), and
minimum (dashed line) stages of the preregulated (upper panel)
and postregulated (lower panel) Missouri River at Omaha,
Nebraska (river kilometer 1107). Preregulated stages are based
on averages of daily stage recordings between 1880 and 1899,
and postregulated stages are based on averages between 1966
and 1985 (modified from Hesse and Me"'. 1993).

Rocky Mountains, to about 45 centimeters in the Great
Plains, and more than 90 centimeters in the interior high-
lands (Hesse and olhers, 1989a).
Annual Missouri River discharge to the Mississippi
River is about 7.0 x 1010 cubic meters. 1\\10 seasonal peri-
ods of flooding occurred prior to impoundmenl (fig, 5-4).
The first, or March rise, was caused by snowmelt in the
Greal Plains and breakup of ice in the main channel and
tributaries. The second, or June rise, was produced by run-
off from snowmelt in Ihe Rocky Mounlains and rainfall
throughout the basin,
In presettlement times the Missouri River was one of
the most turbid river systems in North America. earning it
the nickname Big Muddy. The magnitude of the Missouri
River's sediment load can besl be iIluslrated by its influence
on the Mississippi River. Average turbidity of Ihe Missis-

600
500
400

300
~
.!l
~
.5
c
~
.!!-
<=
o
~
iii

200

100

-.' ~ ~ - ~-

"

'"....'

.. ~".. - -, -..

"

600'

500

400

300

200

100
o

':":

~ ... #..' ..'" -,...,.., -,.,..... -... - - , '.
,

, ,...-1
.If,." ...

,
, "
,,'

o

60

120 180 240
Julian date

300

360

sippi River upstream of the preimpounded Missouri River
was reponed by Platner (I946) as 300 pans per million,
whereas below the mouth of the Missouri River the average
increased to 1,800 pans per million.