A potential storm in the Gulf of Mexico has Mississippi keeping an eye on its development, particularly those on the coast. However, the tropical system could impact Central Mississippi and possibly bring the Pearl River out of its banks and impact a flood-weary Jackson and other areas.
So, why don’t officials at Ross Barnett Reservoir lower the lake in advance of potential storms to help reduce flooding?
Reservoir general manager John Sigman explained.
“No one today can tell me where it’s going to go,” Sigman said. “It may go to Cozumel.
“It may go to Biloxi. History has proven more times than not that storms do not produce what is first predicted.”
Managing the reservoir and dealing with heavy rain across the Pearl River Valley is somewhat like walking a tightrope — it takes balance. The reservoir does have some flood-control ability, but it wasn’t built for that. Its primary purpose is to supply water to Jackson.
Lowering it too far in advance of predicted rainfall could jeopardize the city’s water supply.
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Putting Jackson water supply at risk
“If I lower the lake and it doesn’t rain, I’ve got a dry lake,” Sigman said. “A dry lake this time of year; I may not be able to fill it until January or February. I have to preserve enough water in the lake to meet the needs of the City of Jackson.”
As Sigman pointed out, this is a particularly bad time of year to gamble with the lake level. There may not be significant rain for months.
“Our driest month here in the Jackson area is the month of September,” said Nicholas Fenner, meteorologist with the National Weather Service in Jackson. “We average 3.48 inches.”
Fenner said September and October are in a gap. Summer’s pop-up storms have basically ended and regular cold fronts with associated rains aren’t here, yet. That doesn’t pick up until December when rainfall amounts reach above 5 inches on average and continue through April.
“In general, our cooler season is our wettest season around here,” Fenner said.
Some action is taken at Barnett Reservoir before flooding
During the wetter months, Sigman said the lake is lowered some in anticipation of seasonal rain.
“We keep it at 297.5 (feet above mean sea level) except in December, January, and February,” Sigman said. “We drop it to 296 to accommodate rain. That’s the monsoon season in this part of the world.”
Officials can take some measures before high water reaches the reservoir. Sigman said when forecasters were firm in their prediction of excess rainfall across the basin, discharge at the spillways was increased. Sigman also said because it takes two to three days for rainfall in the Carthage and Philadelphia areas to reach the reservoir, there was even more time to lower the lake.
Even so, the scenario still had its limitations. Sigman said only so much water can be released in advance of incoming water and if done too far in advance of predicted rain, negative impacts can be created for no reason.
“If we start lowering the lake rapidly, by that action you can create a flood downstream,” Sigman said. “If you don’t get the rain, you’ve created a flood unnecessarily.
“The reservoir is not a full-fledged solution to controlling a flood. It helps, but it’s not a full-fledged solution.”
Contact Brian Broom at 601-961-7225 or [email protected].
