Some of us do have a clue. Most of you land has been tiled right? That system has very little water storage capability so it all gets to the rivers real quick, instead of making swamps and marshy areas.
Bingo. read the article and check the Iowas DNR numbers on how much of the original wetlands have been removed, etc. The natural filtering system does it's job and does it well, hence the 500 years.
Also think about all the chit, literal and other things like fert, etc that are now floating around or sinking into the ground water.
I'm not hating on farmers, but there is a reason rivers, etc have wetlands around them and why the wetlands had such fertile soil after they were tiled and drained.
Oh and check my location...we had hella flooding last fall and I'm encircled by farms. I saw the water running down the tile drainage paths last fall and piss pounding into the creeks and rivers.