The massive storm system that has waterlogged Illinois reminds us how much we miss a piece of Illinois’ natural heritage that has been largely destroyed – our wetlands.
Wetlands are nature’s sponges, and the ones that are left offer tremendous flood protection. According to EPA, one acre of a typical wetland can store a million gallons of water, or three-acre feet:
A one-acre wetland can typically store about three-acre feet of water, or one million gallons. An acre-foot is one acre of land, about three-quarters the size of a football field, covered one foot deep in water. Three acre-feet describes the same area of land covered by three feet of water. Trees and other wetland vegetation help slow the speed of flood waters. This action, combined with water storage, can actually lower flood heights and reduce the water’s destructive potential.
Illinois has lost more of its wetlands than most states. According to the Illinois Department of Natural Resources:
When compared with other states, the scope of wetland loss in Illinois becomes more clear. Illinois ranks sixth in overall percentage of wetland loss, behind California, Indiana, Iowa, Missouri, and Ohio. In terms of acres of wetland loss, Illinois ranks fifth. Only Florida, Texas, Louisiana, and Arizona have lost more acres. Because of the large percentage and acreage of wetlands that have been lost, Illinois is in the top 10 percent of states with the greatest overall wetland loss over the past 200 years.
Wetlands are also very good at filtering pollution out of our water supply, and provide critical wildlife habitat for most species. But today we’re especially missing their flood protection superpowers aren’t we?
We’ve lost about 8.5 million acres of our original wetlands. If we still had them today, they’d be keeping 8.5 trillion gallons of water out of basements, streets, businesses, and buildings.
Illinois Sierra Club Blog 
A one acre wetland can only store 3/4 acre-ft of water IF that wetland is completely dry. This year that may be the case because of the drought. However, in North Dakota, all the wetland basins (drained or undrained) are completely full and have almost no additional storage capacity. Please tell the whole story if you’re going to tell the story at all.