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Drought isn't gone yet

Recent rains offer only temporary relief

POSTED: March 20, 2008 5:00 a.m.
Scott Rogers The Times/

A creek empties into Lake Lanier near Longwood Park after Friday morning rain showers. Though rainfall has raised the level of the lake to its highest level since November, experts say the long-range forecast still calls for months of below-average rainfall and above-average temperatures.

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Heavy rains in Northeast Georgia last week pushed Lake Lanier's level above 1,054 feet for the first time since November. But weather officials say the improvement is only temporary.

"Don't get too excited," said state climatologist David Stooksbury at the University of Georgia. "The outlook for March, April and May is still a high probability for below-normal rainfall and above-normal temperatures."

Lake Lanier's normal full pool is 1,071 feet above sea level. On Dec. 26, the lake reached the lowest point in its history, 1,050.79 feet. It has been creeping back up slowly since then, but it needs to rise a lot faster in order to avoid a disastrous summer.

"There's roughly an eight-week period, in March and April, when we get recharge," said John Feldt, a hydrologist with the Southeast River Forecast Center. "It's critical to get rain before the vegetation starts to green up (and pulls moisture out of the soil)."

In February, rain was a fairly frequent visitor to Northeast Georgia, but it didn't stay long. "On average, the Lanier basin was getting a half-inch to an inch and a half at a time," Feldt said. "But for the lake to start rising, we need at least two inches, followed by another two inches a few days later."

Stooksbury said the Gainesville area needs about 1.4 inches per week in order to achieve average rainfall for March.

But average rainfall will only maintain the status quo. In a typical winter and spring, Lanier recharges about nine feet. But this year, if the lake manages to rise nine feet from its lowest point, it still will be 11 feet below full pool.

Based on projections of below-normal rainfall, the U.S. Army Corps of Engineers estimates that Lanier will be at 1,052.7 feet by April 4, more than a foot lower than it is now.

Without a major event such as a tropical storm, Lanier's chances of refilling will rapidly diminish after April. With warmer weather, more of the lake's surface water will be lost to evaporation.

Stooksbury said evaporation only accounts for about 40 inches of loss each year. "It's not a huge factor," he said. "The determining factor is what the corps does at Buford Dam."

When summer-like temperatures arrive, the corps lets out more water in order to generate hydropower.
"Generally in April, we have to start releasing more from the dam," said Lisa Coghlan, spokeswoman for the corps' Mobile, Ala., district office, which controls Lanier.

She said the corps still is releasing only enough from Buford Dam to maintain the Chattahoochee River's required minimum flow of 750 cubic feet per second at Peachtree Creek in Atlanta.

However, during most of February the flow from Buford Dam hovered between 620 and 630 cfs. Since Feb. 26, the outflow has ranged from 1,180 to 972.

The other lakes on the Chattahoochee south of Lanier are full and don't need extra water. But Coghlan said the corps has increased the amount released from Buford because power plants downstream asked for greater flow in the river.

Power demand will continue to rise as summer heats up. Last June, for example, daily releases from the dam were as high as 2,640 cfs.

Stooksbury said it's likely that Lanier will reach a new record low this summer. "People who depend on the lake need to prepare for lower water levels," he said.

The bright spot, he said, is that recent rains should enable Northeast Georgia to have what appears to be a normal spring. "Right now, there's enough moisture in the topsoil for blooming plants," Stooksbury said. "But trees need deep soil moisture. The next six weeks will be critical for them."

He said the worst period for Lake Lanier will be from June through October, when the lake will continue to drop unless there are frequent heavy thunderstorms or the remnants of a hurricane.

Feldt said the summer could be wetter than spring this year. "The computer models show the La Niña (a climate phenomenon that causes dry weather in the Southeast) easing by summer, so that could help a bit," he said.

The absence of a La Niña doesn't mean the drought is over. But Feldt said we could be seeing the light at the end of the tunnel.

"Major droughts usually last two to three years. We're coming up on two years now for this one," he said. "The good news is that it doesn't take as long to get out of a drought as it does to get into it."



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