Last year, Illinois saw record-breaking flooding across most of the state, and this spring’s recent heavy precipitation is causing communities near the Illinois River to prepare for further rises in water levels in the coming days.
Floods in Chicago last week and flood risk along the Illinois and Mississippi Rivers are another sign of growing annual rainfall levels due to climate change, says Illinois State Climatologist Trent Ford.
Precipitation has increased across the state at a rate of about half an inch per decade over the last century. Within the last 30 years, it’s been closer to an increase of one and a half inches per decade. That’s largely caused by increases in global average temperatures, as warmer air has a higher capacity to hold more water vapor, Ford says.
“The long-term change in precipitation across Illinois is the single most impactful change in our climate over the last 100 years,” Ford says. “That’s mainly because the magnitude of change in precipitation is so large, and the impacts from that are just more intense.”
Those impacts include more flooding of residential areas and damaged infrastructure. But one of its biggest impacts in the state is on agriculture—even in areas that aren’t close to rivers, like Champaign County.
“The biggest impacts in Champaign and Champaign County are agricultural impacts,” Ford says. “And one of the biggest issues related to flooding and its impacts on agriculture is of course delayed planting, also soil runoff and nutrient runoff.”
2019 was the 5th wettest year on record in Illinois. In 2017, Chicago experienced its wettest May on record. The May record was broken in 2018, 2019 and now 2020, Ford says.
Last week, Gov. J.B. Pritzker issued a state disaster proclamation for four counties along the Illinois and Mississippi Rivers, including Grundy, Pike, Scott and Morgan, to assist in flood response efforts. Some of the areas that have historically been vulnerable to flooding include Ottawa, Peoria and Beardstown, along the Illinois River.
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