COLLEGE STATION (April 23, 2009)—Despite recent rains, parts of Central Texas remain in the grip of drought, and determining when the dry spell has ended depends a lot on the type of drought you’re talking about.

There isn’t just one specific definition or category of drought,” said Dr. Travis Miller, Texas AgriLife Extension Service statewide agronomist in College Station.

There are four generally acknowledged types of drought, Miller said, meteorological, hydrological, socioeconomic and agricultural.

Meteorological drought is the one with which most people are familiar. It refers to periods when precipitation for a region is less than the historical average, Miller said.

Hydrological drought refers to the impact of reduced rainfall on water supplies, Miller said.

Socioeconomic drought refers to periods when a lack of precipitation adversely affects a region’s economy, Miller said.

And agricultural drought, which is widespread now through Central and South Texas, refers to the dry ponds, bare fields and slow-to-green pastures that characterize dry spells, Miller said.

“The agricultural economy in drought-stricken areas of the state is impacted because it’s either too dry to plant crops or the crops are withering, and ranchers are feeding livestock hay or other supplementation when they would normally have green grass and full months sooner,” he said.

Mark Lenz, a meteorologist with the Austin/San Antonio National Weather Service office in New Braunfels said about 10 to15 inches of rain over the next several months would put most of South Central Texas back on track and make it reasonable to proclaim the drought has ended.

“Even after the rains in late March, each of the 33 Texas counties which this office serves are still either in extreme or exceptional drought,” he said.

“People are often under the impression that after a couple of days of good rains a drought has broken, but that only happens if precipitation over a period of months puts us near the long-term average.”

“That’s only true if those rains are longer, soaking rains as opposed to hard rains where there are flash floods and a lot of runoff,” he said.

“While a hard rain might help replace some surface water, it won’t penetrate the subsoil enough to be helpful to farmers and ranchers.”

The drought in extreme South Texas is rated severe, and Nezette Rydell, a meteorologist at the National Weather Service in Brownsville, said she does not expect improvement anytime soon.

“The weather patterns are not giving us great hope,” she said.

“In general, it’s not looking favorable for the chances of rain.”

But the news isn’t entirely bad, according to Dr. John Nielsen-Gammon, Texas' state climatologist, College Station.

“Parts of the central and far western Texas Panhandle as well as parts of extreme West Texas have received sufficient rainfall to say they are now in the process of recovering from drought,” he said

Forecast information from Nielsen-Gammon’s office suggests La Nina will weaken significantly in May and June, and that in the fall El Nino will “take over the Pacific Ocean,” creating conditions which should “produce a wetter, cooler Texas climate and give Texas the rain it has been looking for.”

While it’s difficult to determine exactly when a drought is over, there are still points of general agreement, Nielsen-Gammon said.

“I think most experts would concur that a drought is over when rainfall is close to the long-term average, ground moisture is adequate for normal dry-land crop growth and to provide sufficient livestock forage, and lakes, reservoirs, ponds and stock tanks are full or nearly full,” he said.

"However, while a drought may be over, the impact of drought to local economies and to agricultural production can be longer lasting,” he said.