By Captain Matthew P. Collins
L
ast summer's Midwest drought was unlike any in
several decades, causing water levels in the Mississippi River to drop to near-record lows. The U.S.
Army Corps of Engineers (USACE), St. Louis District, one of
six districts in the Mississippi Valley Division, is authorized
by Congress to maintain a 300- by 9-foot navigation channel
in the river. The channel effciently carries massive amounts
of raw material that the United States
imports and exports, including corn,
wheat, soy, coal, liquefed natural gas, and
other commodities. Lock 27 (the river's
southernmost lock) allowed more than
80,000,000 tons of cargo to pass safely at
Granite City, Illinois, in 2011. The channel
connects ports throughout the Midwest to
the rest of the world through the Port of
New Orleans. The channel is maintained
in three ways: locks and dams, river training structures, and rock and sediment
removal. This article focuses on how the
St. Louis District and the Mississippi
Valley Division use all three methods to
maintain a safe and reliable navigation
channel during droughts.
Minnesota, and Granite City. Each lock is meant to pool
water upstream and has the added beneft of helping to
regulate the depth of the river downstream. The area below
the last lock is typically the most affected during droughts
because there is no pool effect. The most affected region
extended to the confuence of the Ohio River, where the
depth of the Mississippi increases naturally.
Locks and Dams
O
n the upper Mississippi River,
locks and dams create a stairstep effect to hold back water and
allow ships to travel through. There are
29 lock-and-dam sites between St. Paul,
May–August 2013
Chevron-shaped training structures direct the fow of the river.
Engineer 21