DES MOINES — Iowans who like to talk about the weather and the pros and cons of climate change got a double dose of information to consider recently.
In the near term, a team of Iowa experts in natural resources, agriculture, homeland security and the U.S. Geological Survey reported parts of the state are beginning to show signs of stress in groundwater conditions for the first time in a year.
Dry conditions continue to slowly expand, according to the state experts’ latest water summary update, raising concerns that below-normal summer rainfall is leading to drought conditions in parts of Iowa. Statewide summer rainfall was 10.74 inches, or nearly 3 inches below normal.
“For the third month in a row, Iowa received below-normal rainfall. After such a wet start to the year, the below-normal rainfall has pushed more than half of the state into abnormally dry or moderate drought conditions,” said Tim Hall, coordinator of hydrology resources for the state Department of Natural Resources.
More than half of Iowa was rated as abnormally dry, according to the National Drought Monitor, while streamflow conditions in areas away from border rivers have moved into the normal flow range, he said.
Hotter & wetter
Looking long term, James Boulter, an associate professor of chemistry in the Watershed Institute for Collaborative Environmental Studies at the University of Wisconsin at Eau Claire,
issued a report earlier this month indicating Iowa is becoming hotter and wetter, a trend he attributed to climate change.
Policymakers and community leaders will face economic and health challenges with more frequent flooding that may become more extreme as the climate changes, he said.
Boulter noted statewide damage estimates from the 2019 flooding are staggering and likely to rise, as western Iowans struggle with Missouri River flooding that led to 47 levee breaches. Iowa’s eastern border, he said, underwent 38 days in which the Mississippi River topped flood stage.
“Science is giving us warnings,” said Boulter, whose report — available at iowapolicyproject.org — was supported by a grant from the Environmental Defense Fund in concert with the Iowa Policy Project, a liberal-leaning nonprofit public policy research and analysis organization in Iowa City.
“Even those who have not lived it have seen the pictures of rooftops surrounded by floodwaters, breached levees, destroyed grain bins and impassable roads,” he said. “Flooding is getting worse, and we have public policy options that can lessen the impact in the coming years.”
Boulter said average temperatures in Iowa have risen 0.4 degrees Fahrenheit per decade over the past four decades, which represents an increase of almost 5%.
Iowa’s rainfall from May 2018 to last April topped 50 inches — breaking a 116-year-old record by about 2.5 inches.
More intense rainfall
He also said snow accumulations in Iowa, Minnesota and Wisconsin were substantially higher while rainfall in the Upper Mississippi River Basin has risen steadily and high-rainfall days have become more intense.
“A range of climate models predict that by 2041 to 2050, there will be another 30% increase in the frequency of two-day precipitation events whose rainfall totals set a five-year record,” he added.
Boulter’s report noted flooding in Iowa this year appears to be a repeat of other recent “100-year flood” events such as those in 1993, 2008 and 2011.
A recent report by the Iowa State University Institute for Transportation found that “for the Cedar River Basin in Iowa, the 100-year flood ... of the 20th century is projected to be a 25-year flood in the 21st century, with associated increased frequency of flooding of agricultural land,” according to Boulter’s report. “Iowans have to wonder — is this our future in a changing climate?”
Boulter’s report compares the Intergovernmental Panel on Climate Change future scenarios in which society makes choices to mitigate its impacts on the global climate, concluding that the least-ambitious response is consistent with some of the most-alarming potential climate outcomes.
Conversely, future climate impacts could be greatly reduced by a “more-robust” response that exceeds the emissions reductions the United States previously committed to in the 2015 Paris Accord.
“The study makes a compelling argument that a changing climate may produce more historic-level floods in the region and that the conditions that led to the 1993 floods may become a new normal,” said Boulter, who told Iowa reporters on a conference call that “in one way or another, policy responses are inevitable. The question is do we do them now in a proactive way or do we do them much later in a reactive way at which point they will be much more expensive and much more intrusive. That’s really the question that we have to ask.”