Palmer Drought Severity 1019

The Palmer Drought Severity Index calculates that it would take 12 inches of rain over a 30-day period to catch the lake level up to the rule curve.

T

he lake is lower sooner this year. While the rule curve registered with the Federal Energy Regulatory Commission prescribed a Lake Martin pool level at 487.91 feet on Oct. 18, the lake level was only up to 486.84 feet, leaving the water level about 1 foot below the rule curve. That puts the annual fall drawdown about two weeks ahead of schedule.

Since October historically is the driest month of the year, it’s unlikely that the river basin will receive sufficient rainfall to bring the water level back to the rule curve this year, said Alabama Power Reservoir Management Manager Alan Peeples.

“It would take 12 inches of rain over a month-long period to get back to a normal situation, according to the Palmer Drought Severity Index recently released by the National Weather Service,” Peeples explained. 

The lower water level is the result of an extreme drought in the Lake Martin area, coupled with a late summer heat wave that escalated evaporation rates, he said.

“July was very dry. We got a little bump up with a rain event in August, but it really wasn’t enough to get us back where we needed to be. Then we had a really severe September. That took a toll across the whole system. We’re a foot below the rule curve, and some of that is due to high evaporation rates. About 6 inches of that is evaporation,” said Peeples.

“We’ve cut downstream releases at Thurlow Dam as much as we can to still meet the minimum flow requirement, but it’s more than what we have coming in,” Peeples added. “The Army Corps of Engineers requires a minimum flow to support navigation downstream.”

Once the lake level reaches 484 mean sea level feet – the winter pool for Lake Martin – rainfall amounts will determine whether the lake stays at or drops below the winter pool level.

“If the rains are good, we should be able to stay on it. If it’s dry, we may have to lower it more,” he said.

Some good news in this story, Peeples said, is that the National Weather Service Climate Prediction Center recently released projections that show a neutral probability of drier-than-normal or wetter-than-normal conditions for December through February.

“It’s good news in that they aren’t confident enough to forecast dry conditions,” Peeples said.