Drought not going away

It may be a damp week, but even if the year-to-date rainfall deficit for Chattanooga of 7.62 inches were erased, drought will persist in the Tennessee Valley.

“Because the drought has been so severe, it will take seasons worth of near-normal rain to get us back to where it is not so dry,” WTVC NewsChannel 9 chief meteorologist David Glenn said. “In this part of the country, even in a dry year, we know it will get wet again.”

The mid-South’s current drought developed slowly over the course of months and years, according to meteorologists and climatologists.

They say a drought’s demise requires several seasons of above-normal precipitation, and experts do not expect a rapid reversal of rainfall deficits that have been building here for about two years.

“It is always hard to tell when a drought starts, but we use March 2006 (as a starting point),” Georgia assistant state climatologist Pam Knox said.

Ongoing drought means aquifers are not being replenished, while lakes and rivers that show near-normal water levels have reduced flow, she said.

“This is not something that started in 2007,” said Tom Womack, spokesman for the Tennessee Department of Agriculture. “We had about 40 counties in 2006 that qualified for drought designation, and it has gotten progressively worse.”

Ken Givens, the state’s agriculture commissioner, said the full extent of drought-related damage may not be realized for several years, but drought losses for Tennessee’s farmers, foresters and nurserymen already could total between $750 million and $1 billion.

“There’s no way around it,” Gov. Phil Bredesen writes in the Department of Agriculture’s annual report. “The 2007 crop year will go on record as one of the most, if not the most, devastating for Tennessee agriculture.”

Dry topsoils

Recent rains have not moistened topsoils very much, according to a report prepared in February by Brian Boyd, senior hydrologist for the National Weather Service in Morristown, Tenn.

The top 16 inches of soil — the root zone that is critical for seed germination in spring — are quite dry, with the driest areas in extreme Southeast Tennessee and the mountains along the border with North Carolina, he said.

The deeper soil layer, down to about 6 feet, is much drier than normal for the season, as even moderate to heavy rains have failed to penetrate to that depth, Mr. Boyd said.

Throughout 2007, demand for water outstripped supplies across the Southeast — reservoirs were at record-low levels, crops failed, timberlands resembled tinderboxes — and it seems conditions will improve little during 2008, experts said.

“What we are in now is one of the worst (droughts) of the past 100 years,” Ms. Knox said. “We could see significant reductions in drought conditions over the next few weeks, but after April 1, every bit of moisture that falls either will be used by plants or lost by evaporation.”

Recent rains, particularly in South Georgia where as much as 7 inches of rain fell during the past few weeks, have helped refresh aquifers, Ms. Knox said.

Reservoirs that supply water to Atlanta have continued to feel the effects of drought and a growing population, officials said.

Georgia’s capital city relies on Lake Lanier, formed by damming the Chattahoochee River in the 1950s, for about 75 percent of its water. The remainder mostly comes from Lake Allatoona.

The Chattahoochee, Chesatee, Etowah and other North Georgia rivers flowed at less than half of their normal rates in January, according to Dr. David Stooksbury, the state’s climatologist.

Through late February 2008, the water level at Lake Lanier had risen less than 3 feet from the record low set on Dec. 28, 2007, according to the Peachtree City, Ga., office of the National Weather Service. In a typical winter the lake will rise about 9 feet.

“I’ve never seen them close the boat ramps,” said Denise Kiely, manager of Carters Lake Marina & Resort near Ellijay, Ga., referring to the U.S. Army Corps of Engineers ordering boat ramps closed due to low water levels last September.

Winter rains and rising lake levels allowed ramps to reopen in mid-February, but the lake remains below normal, she said.

“We just hope for rain in March,” Ms. Kiely said.

Tropical weather

Meteorologists and climatologists said in recent months a moderate to strong La Niña climate pattern took hold in the Pacific Ocean. Such a pattern usually means the Southeast has temperatures above normal and rainfall below normal through spring.

“La Niña ruled through the December-February period,” Mr. Glenn said. “We had milder temperatures and 11 inches of rainfall that was slightly — about 4 inches — below normal for the season.”

La Niña is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, as compared to El Niño, which is characterized by unusually warm ocean temperatures in the Equatorial Pacific, according to the National Weather Service.

As the La Niña grew last year, it reduced the number of tropical storms that bring Gulf of Mexico moisture to the Southeast. But La Niña is breaking down and losing its control over climate, Mr. Glenn said.

The weaker influence of La Niña may allow a return to more active storm and hurricane seasons, he said.

“We have to be aware that Texas was like us about four years ago, now they are saturated,” he said.

Ms. Knox said tropical storm activity in the Atlantic Ocean could increase this year, causing more moisture-bearing storms to come ashore either from the ocean or the Gulf of Mexico.

“We know it will likely be active but have no idea where or how strong the storms will be or where they will make landfall,” she said.

Mr. Boyd predicts temperatures and rainfall should be about normal through the early summer, and “until we get above normal rain for months on end, the drought will be here.”

He said droughts “are not busted, they quietly go away.”