Lower Mississippi River would be four feet less mighty without Twin Rivers
By Lee Roberts
NASHVILLE, Tenn. — The lower Mississippi River would be four feet less mighty if not for the water storage reservoirs along the Tennessee and Cumberland rivers and their tributaries that provide a stream of water management benefits.
In support of current drought conditions on the lower Ohio and Mississippi Rivers, water is being released at a rate of 41,000 cubic feet per second from the Tennessee River and 12,000 cfs from the Cumberland River.
According to water managers in the U.S. Army Corps of Engineers Nashville and Memphis Districts, the Tennessee and Cumberland River Basins represent about six percent of the drainage area above Memphis. However, the basins are currently providing one half of the water flowing in the lower Ohio River, and one third of the water flowing in the Mississippi River at Memphis, Tenn.
David Berretta, chief of the Memphis District Hydraulics and Hydrology Branch, said contributions from the Tennessee and Cumberland Rivers are very important to the Lower Mississippi River. He reports that currently there are no navigation issues in the Memphis District, although the towing industry in conjunction with the U.S. Coast Guard is limiting tow sizes and are "light loading" barges.
"The level on the Mississippi River would absolutely be at a historical low if it were not for the water from the Tennessee and Cumberland rivers," Berretta said.
Water managers in the Nashville District said the system of dams and reservoirs were built to provide water resources during months of limited rainfall, which is proving its worth now during a drought throughout the middle of the country.
"The ability of our reservoir system projects to store water has made it possible for the Cumberland River to pay a big role in supporting water levels on the lower Ohio and Mississippi Rivers" said Bob Sneed, Nashville District Water Management Section chief.
The Nashville District operates Barkley Dam in Grand Rivers, Ky., which is the last downstream dam on the Cumberland River. The Tennessee Valley Authority operates Kentucky Dam, also in Grand Rivers, Ky., which is the last downstream dam on the Tennessee River. Working in conjunction with the dams upstream, the two dams on the Twin Rivers can either hold water or pass water as necessary in support of water management requirements that support the nation's overall system of waterways.
TVA and Corps water managers have been coordinating and working hard this year to manage the reservoir systems and the purposes of the projects, which include flood risk reduction, commercial navigation, water supply, water quality, hydropower, recreation and environmental benefits.
"TVA's river operations staff has worked all summer to keep TVA reservoirs and river levels as high as possible despite below average rain and runoff. This has allowed TVA to provide minimum flows that are having a significant contribution to the Ohio and Mississippi rivers. This illustrates the regional and national benefits of TVA's integrated and balanced river management approach," said John McCormick, TVA senior vice president, River Operations and Renewables.
The Mississippi River in Memphis is at its fourth lowest level since record keeping began in the 1920s. The levels of the Mississippi River and Ohio River at their confluence in Cairo, Ill., are at the 12th lowest level since record keeping began in the 1870s and sixth lowest level since the system of modern dams was constructed.
Berretta said as of this morning, The Cairo gage at the confluence of the Ohio and Mississippi rivers is 8.1 feet. The average for August and September is about 17 feet on this gage. He also said the Memphis gage is at -9.3 feet. The record low at this location was -10.7 feet in 1988.
US Army Corps of Engineers