Low Water Levels Threaten Mississippi River Navigation
Date Posted: November 29, 2012
This article is reprinted from the USDA's Nov. 29 Grain Transportation Report.
The 2012 drought has significantly reduced water levels on the Mississippi River, threatening the barge movements of agricultural goods and inputs.
Since late spring, there have been constant disruptions to waterway traffic on the Mississippi River System.
Drought conditions have caused low water levels that have forced barge operators to use narrower navigation channels and constantly anticipate the depths of the river.
Barge operators have light-loaded barges and it has taken more barges to move the same amount of grain.
Temporary river closures caused by grounded vessels have become common this year, especially since last year’s flooding added additional sediments to the river bottom.
Currently, the primary area of concern is between St. Louis, MO, and Cairo, IL (see map in Figure 1).
The Missouri River, above St. Louis, significantly contributes to the water levels of the Mississippi, as much as 60 percent in a normal year.
The Ohio River further south also supplies a significant portion of the water for navigation on the lower Mississippi River at the Cairo junction.
In addition to the problem of low flows above St. Louis, another contributing factor to the current concern on the Mississippi River is the U.S. Army Corps of Engineers (Corps), on November 23, began reducing flows from Gavins Point Dam, near Yankton, SD, as part of an annual process designed to preserve water during the winter.
In managing water flows for the Missouri, the Corps is constrained by their obligation to balance the needs of all the river’s users.
Water from the Missouri River is needed for navigation, flood control, hydropower, water supply, irrigation, recreation, water quality, and fish and wildlife habitat.
As a result of low water supply from the Missouri River, water levels at St. Louis on the Mississippi River are dropping and could approach if not exceed historic lows.
For all of 2012, St. Louis River levels have been below the 10-year average.
Without an increase in rainfall, and with the reduced flow from the Missouri River, the Corps using National Weather Service data projects the Mississippi River gage at St. Louis to drop to a low of -5 feet on or about December 10, causing the rock formations in the low water to become a hazard to navigation.
These formations have always been in the river, but until now there has always been sufficient water depth to prevent interference with navigation.
The reduction of Missouri River flows and the current drought could prohibit allowable drafts for loaded barge operations.
Barge operators are wary of potential dangers when navigating around submerged objects, and rock pinnacles may block most, if not all, of the navigable channel in the area.
Rock Removal Project
Rock pinnacles in the river near Thebes and Grand Tower, IL, will pose a risk to navigation. The Corps, in partnership with the Coast Guard, has provided electronic charts of the pinnacles to mariners.
Rock removal is planned to provide a more reliable channel as low water conditions continue.
The Corps expects to begin the rock removal by February 2013. Based on past actions by contractors for the Corps on other projects, the process would likely consist of a drill barge boring openings into the submerged rocks.
Explosives would be placed in the holes and detonated, with the rock debris then removed from the channel.
Barges would not be allowed to pass the site while these operations are performed.
At this time, it is unknown how long the process will take or whether it will be one continuous operation or conducted in stages to allow intermittent barge traffic.
Impact of Closure
Starting in mid-December the drought and reduced Missouri River flows will limit or possibly stop navigation on the affected stretch of the Mississippi River.
During a slowdown or stoppage, all export grain barge movements north of the impacted areas would be affected. Since the Illinois River flows into the Mississippi River above St. Louis, export traffic on that river would also be affected.
This time of year is important because barges move a significant amount of grain out of the Upper Mississippi River before the winter season.
Usually, most of the Upper Mississippi River (above St. Louis) is closed from mid-December to late March due to ice accumulations and winter maintenance.
GTR Figure 10 shows that historically average weekly tonnage for Locks 27 normally increases significantly during late November and into December.
In addition, the Mississippi River Locks 27—the southernmost locks on the Mississippi River near St. Louis, MO—will have its main 1,200 foot chamber closed for repairs from December 10, 2012, to March 1, 2013.
The smaller auxiliary 600 foot chamber will be open during that period, but there will probably be delays because traffic will have to wait to use the smaller chamber.
Importance to Grain Exports
Barge movements are important to grain exported through the Baton Rouge-New Orleans Mississippi River ports.
Based upon 2006-10 data, barges using the Mississippi River carry 54 percent of corn exports and 46 percent of soybean exports.
However, the 2012 drought has reduced corn production this year and U.S. corn exports for 2012/13 are forecasted at 1.150 billion bushels, down 25 percent from last year’s exports of 1.543 billion bushels.
If barge movements are impeded, grain shippers may need to rely on more expensive options of shipping grain, either by rail to Pacific Northwest ports for export, or by moving it by rail to points south of the bottlenecked section of the river.
For more information, call Surajudeen (Deen) Olowolayemo, USDA, at 202-694-3050.