Indiana and Illinois may experience severe droughts in the future, but they'll be few and far between, according to a Purdue University study.

Keith Cherkauer, an assistant professor of agricultural and biological engineering, and Vimal Mishra, Cherkauer's graduate student, used historical data from the National Climate Data Center to model the likelihood of future droughts in the two states. Historic data observed showed that those trends are expected to produce conditions in which droughts would be short, harsh and costly, but rare.

"Historically, a drought like the Dust Bowl would happen every 100 years, but what we've found is that modern droughts are shorter and can be more severe," said Cherkauer, whose results were published in the early online version of the journal Agricultural and Forest Meteorology. "The frequency of these droughts and the aerial extent has decreased significantly, however, since the middle of the last century."

Studying precipitation data from 1916 through 2007, Cherkauer and Mishra found that only one severe drought - in 1988 - occurred since the Dust Bowl era of the 1930s. During that time, Indiana and much of northeastern Illinois have trended toward more precipitation during the crop-growing season from May to October, a positive for corn and soybean growers.

"There is less chance of having widespread, extreme drought," Mishra said. "We may have drought, but the tendency is that we're getting more precipitation during the crop-growing season."

Cherkauer and Mishra predicted future drought conditions by studying historical precipitation trends and inputting soil moisture and stream flow data into the Variable Infiltration Capacity Model, which simulates how precipitation moves through land surface environments.

Cherkauer warned that despite the rarity of drought conditions, droughts would be likely to occur during the later part of the crop-growing season, when the plants need moisture to produce grains.

"Yields are also much higher than they were during the Dust Bowl, so the impact of the damage would be worse," Cherkauer said.

Mishra said future research will try to determine the cause or causes of the increase in precipitation. He said global warming is likely a factor because rising sea temperatures near the equator are causing more El Nino conditions, which increase rainfall in the Midwest.

"We have seen an increase in sea surface temperatures as global air temperatures increase," Mishra said.