I would support siphoning off ten-twenty feet of water from the Mississippi during flood stages from March-June and pumping it to several places including west Texas, the Ogalala aquifer in eastern Colorado and over south pass in southwest Wyoming.
This would both serve as flood control on the Mississippi as well as providing water for points west.
This dual purpose was the original intent of the Hoover dam on the Colorado.
Likely this job will have to wait until portable nukes make electricity much cheaper and power plants drop in easy to post.
As it is this would be money better spent than the current policy of spending 4 billion dollars annually by the Army corps of engineers to dike the Mississippi and do FEMA disaster relief and flood plain buy outs.
If it were practical (perhaps using large, high power lasers from orbit, to bore just barely non-level tunnels) I’d like to see the diversion take place from the eastern watershed (basically, high areas of the Missouri River basin) to the western watershed, iow, feed the Colorado with all of its hydroelectric dams and reservoirs with the annual flood.