We are approaching the confluence of the Upper Mississippi and the Ohio rivers. When I was little, I was told that where the rivers converged a giant whirlpool had formed. Boats had to struggle to not get sucked in. Well, enough barges have gotten sucked into the whirlpool that now it is filled up and all boat traffic glides across.

OK…there is no whirlpool. The two rivers meet and the waters seem relatively calm. Maybe there are some interesting dynamic velocities under the surface that only a Doppler could reveal. Interestingly, the Ohio contributes nearly 75% of the flow to the lower Mississippi River where the upper Mississippi River (where we are now) contributes the remainder. Yet the upper Mississippi River contributes nearly 80% of the sediment to the lower Mississippi. While traversing the confluence in the runner boat, you could see the muddy water and clearer waters mixing. They actually do not become fully mixed until Caruthersville, MO.

The data acquisition is going really well. The data quality has improved from days previous. Some of this may be due to us reducing our drift speed down the river. The big compressor is having a hard time keeping up the high pressures in the day’s heat. To aid the big compressor, we’ll energize less often (~every 8 seconds instead of 5), thus we need to move slower down the river. The data quality decreases when we approach a dike or revetment. The energy excited into the water expands spherically and will reflect off the underwater dikes and river bank revetments producing unwanted signal response. On this day, the channel narrowed along the bends that made it difficult to avoid these features. A dike is a line of piled rocks extending into the channel that force the river to a specific path. This helps to keep the river channelized thus reducing the need to dredge. Boats need at least a 9 ft freeboard to navigate the river. A revetment is a blanket of inter-locked concrete pads that stabilize the banks.

In all it was a really good day.