The mystery photograph is a close-up from this. An anchored river dredger pulling up silt from the recent Mississippi River flooding and depositing it in a tethered, open top, barge adjacent to the dredger.
The muddy water is pumped up from the river bed, and then passes over the barge. The heavy silty sludge falls directly into the barge, separating itself out from the river water. Some of the water goes right over the barge in that high stream that you see, and rest splashes over the side of the barge back into the river.
As I watched, the tug boat was slowly moving the barge in relation to the dredger so that each compartment on the barge was filled. Once it was completely filled, the dredger shut down.
An entertaining spectacle for my lunch time by the Mississippi in downtown St. Louis today.