Tuesday, March 31, 2009

March rain relieves Georgia drought

An unusually wet March has brought major drought relief to north Georgia. Only the Lake Lanier and Lake Hartwell basins are now in drought. The remainder of north Georgia is drought-free.

Abnormally dry to moderate drought conditions continue across south Georgia, however.

Though relief has come, long-term rainfall deficits are still a concern. Small and medium reservoirs are full. The major exceptions are Lake Lanier and the Savannah River Valley reservoirs Hartwell, Russell and Clarks Hill.

Rain across the piedmont and mountains have resulted in the soil moisture being near normal for the end of March. However, soils across south Georgia remain abnormally dry.

The counties in north Georgia classified as being in moderate drought are Union, Towns, Rabun, Lumpkin, White, Habersham, Hall and Stephens. With the exception of northwest Georgia, which has normal moisture conditions for late March, the rest of north Geogia is classified as abnormally dry because of long-term rain deficits.

Coastal plain counties in south Georgia are classified as being abnormally dry or in moderate drought. Abnormally dry counties are south and west of Muscogee, Chattahoochee, Marion, Schley, Sumter, Lee, Worth, Colquitt and Brooks. The remaining coastal plain counties are classified as being in moderate drought.

Currently the climate pattern is a weak La Niña pattern tending toward a neutral pattern. A typical weak La Niña spring brings wet weather across the northern piedmont into the mountains, just like north Georgia experienced in March.

However, across the coastal plain and southern piedmont, a weak La Niña spring is usually warm and dry. Outside the series of storms that crossed the coastal plain over the last several days, the expected La Niña pattern has occurred.

Moisture conditions are in good shape across most of the state’s northern half, but the typical moisture recharge period will be ending soon. By the middle of April, plants are in full spring growth and using tremendous amounts of water.

By the middle of April we can expect the soils to begin to dry because of increased plant water use. Additionally, by the middle of April, temperatures are routinely in the 70s to low 80s. This means that evaporation will increase. This late spring and summer drying is normal.

The outlook is for a few more weeks of recharge followed by the normal drying of the soils due to plant water use and evaporation. May is usually a dry month. Little recharge is expected from May through October, but this is typical for Georgia.

The big unknown is what the tropics will bring Georgia this summer and winter. Much of the state’s late summer and fall rain comes from tropical disturbances. Without moisture from the tropics, August through October can be very dry. At this time there are no clear indications of how much rainfall the summer will bring.

By David Stooksbury
University of Georgia

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