Ship traffic on the Mississippi River was briefly shut down yesterday and salt from the Gulf of Mexico is threatening the drinking water upriver as the severe drought has pushed water levels far below their usual depths. 

According to The Associated Press, the Army Corps of Engineers built an underwater barrier in Louisiana yesterday—temporarily stopping ships from moving past New Orleans—to try and halt the encroaching salt water, which is no longer being held back by the force of the mighty Mississippi. (Which might actually be good for the Gulf, but that's another story.) Further upstream in Vicksburg and Memphis and into Illinois, water levels have dipped to all-time lows. One year ago the river was hit with record flooding, which raised water levels to new heights, but also deposited tons of soil on the river bed, actually making the river shallower. NBC's John Yang says that in Tunica, Mississippi, the river is currently 10-12 feet below "normal" water levels and 57 feet below last year's flood peak.

This year, which has been one of the hottest and driest in the history of the nation, has pushed the water back down exposing sand bars, rocks, other debris and closing shallow ports. There have already been several instances of river barges running aground, leading other shipping companies to lighten their loads and travel at slower speeds to avoid similar accidents. Near St. Louis, the Corps has been continually dredging a nine-foot-deep channel in order to keep waters deep enough for ships to pass through on their way south. The river is a mess and the inability to move goods through major ports will only drive up the cost of buying and selling them.

In both last year's flood and this year's drought, few are willing to definitively point the finger at climate change, but in this particular instance there's only one solution: Rain.