The contrast is illustrated in these two images, which show a stretch of the river just south of Memphis, Tennessee. Landsat 7 captured the top image on August 8, 2012, while Landsat 5 took the lower image on August 14, 2011. (The images are rotated so that north is to the left.) In the August 2011 image, the river was three months removed from the peak of the floods, and river gauges recorded levels close to normal for the month. In August 2012, water was several feet below the historic normal stage for Memphis, and many sandbars were newly exposed or greatly expanded.
As of August 17, 2012, river gauges in the Memphis region recorded levels at -2.4 to -8.3 feet (below historic normal stage). At the time of the August 2011 image (lower), the river stage was 11.7 feet. (In May 2011, the river peaked at 56.6 feet in the same location.)
The Mississippi River is a major North American transit route, carrying goods to and from ports in New Orleans and Baton Rogue. The top image shows that low water levels have narrowed the river from a superhighway to a small road. The U.S. Army Corp of Engineers maintains a 9-foot shipping channel in the lower Mississippi and has dredges working around the clock to keep the channel clear. Not only are water levels low in 2012, but the floods of 2011 dropped a layer of sediment on the riverbed, reshaping previously open channels.
The reduced river flow in 2012 has translated into millions of dollars in extra shipping costs, as the loss of just one inch of draft means that a barge can carry 17 tons less than it otherwise would. The result is decreased shipping capacity.
Reduced water levels had one positive impact: The U.S. Army Corp of Engineers has been able to access and repair levees that were damaged in last year’s floods. The levees are the tan lines that surround the river in these images.
The low water levels followed record-setting temperatures and dry weather. By the end of July, 63 percent of the contiguous United States was in drought, affecting both crops and water supplies.
- Advanced Hydrologic Prediction Service. (2012, August 17). Mississippi River at Memphis. NOAA National Weather Service. Accessed August 17, 2012.
- Advanced Hydrologic Prediction Service. (2012, August 17). Mississippi River at Helena. NOAA National Weather Service. Accessed August 17, 2012.
- American Waterways Operators. (2012, July 20). Nation’s waterways operators concerned about the impact of drought conditions, low water levels. Accessed August 17, 2012.
- Mississippi National River and Recreation Area. (2012, August 1). Mississippi River Facts. National Park Service. Accessed August 17, 2012.
- National Climate Data Center. (2012, August). State of the Climate National Overview for July 2012. NOAA. Accessed August 17, 2012.
- U.S. Army Corps of Engineers. (2012, August 9). Communication, cooperation and coordination key to keeping Mississippi River open for commercial navigation. Accessed August 17, 2012.
- U.S. Army Corps of Engineers. (2012, August 3). Mississippi-Ohio River confluence update. Accessed August 17, 2012.
- Yang, J. (2012, August 15). Drought sends Mississippi into ‘uncharted territory.’ NBC News. Accessed August 17, 2012.
- Landsat 7 - ETM+