By MATTHEW D. ERNST
COLUMBIA, Mo. — Managing weather extremes is a topic close to farmers as drought persists in much of the country. But an Iowa State University scientist told the fourth annual Agroforestry Symposium in Columbia Jan. 9 that, for Iowa, his models predict a likely normal moisture year in 2013.
Chris Peterson, assistant director of ISU’s Climate Science Program, gave his keynote presentation focusing on warm-season rainfall extremes in Iowa: spring flooding and summer drought.
He presented data showing the frequency of spring floods in Iowa has increased.
“What was a one-in-10-year event in previous years (1873 to 1980) is now a one-in-three-year event, in the previous 30 years,” he said.
The more recent trend in Iowa is toward wetter summers, said Peterson. “The number of years that are wet in the summer (July through September) has increased from one in 10, during this 108-year period to one in six during this 30-year period,” he said.
The probability of extreme droughts in Iowa, though, is about as likely as in the past. Peterson noted spring rainfall is not a predictor for summer rainfall. “There’s no correlation between summer and spring rainfall,” he said, noting the pattern looks like “buckshot.”
Floods and drought create obvious challenges for agriculture and agroforestry: soil erosion and nutrient loss from flooding, plant stress and crop failure in drought. Many row crop producers in Missouri, southern Illinois and southern Indiana experienced severe drought last year.
Flooding along the Mississippi and Missouri Rivers in 2012 created catastrophe for some producers in those flood plains.
For 2013, Peterson said historical conditions indicate a wetter than normal spring is likely. “Under the El Niño conditions that we’re experiencing right now, historically there’s been an increase in rainfall across the Midwest in March (to) May,” he said.
“Our best guidance suggests that we’re in very good shape for this year. It has a very good chance of recharging our soil and giving us some water back into our rivers by the time May rolls around this year.”
Based on historical trends, he said, a normal crop year is likely for 2013. Beyond next year, though, Peterson’s current analysis indicates drought conditions may be trending more likely in the region from Oklahoma to the Ohio River Valley, from 2020-40.
He cautioned the weather models are still in development, but his current analysis indicates when there is a drought, there will also be a greater risk for higher temperatures.
That risk, in drought years, describes the experience in much of Missouri last year. Last week, USDA Secretary Tom Vilsack announced 31 counties were designated primary disaster areas due to drought and heat. Many more counties in Texas, Kansas and Oklahoma are also designated as drought disaster areas.
Such extremes may be more frequent in the future, said Peterson. “At the moment, the best we can say is we have to prepare for a much broader range of summertime outcomes,” he explained.
Increase in spring rainfall will be welcome in many parts of the Midwest that are still dry. Last week, the U.S. Army Corps of Engineers continued blasting of rock on the bottom of the Mississippi River near Thebes, Ill. The hope is barge traffic will be able to continue, buoyed by the previous weekend’s rainfall in the region, until the usual slowdown of barge traffic in late January.
For the future, it appears the weather may be even more unpredictable.
“It appears that, in 2013, a dry spring and dry summer is unlikely, given our historical precedents,” said Peterson. “For 2020 to 2040, it suggests that there is a higher frequency of drought and higher temperature when there are droughts occurring.
“For 2014 to 2100, it appears that the warming climate will have an increasingly greater impact on rainfall variability. That means we’ll have a broader range of extreme rainfall.”
The longer-term implications for agriculture and agroforestry, said Peterson, are obvious: nutrient management, soil conservation and cropping practices may need to be adjusted in the longer term. But for this year, according to the climate scientist, normalcy may return in the Corn Belt.
“The historical trend is that we have a good crop year coming up,” he said.