The shipping industry in St. Louis wants the White House to order the release of more water from the Missouri River, which flows into the Mississippi, to keep waters high enough for the long barges that float down the river to New Orleans.
Foster said the extra water would be for 60 days or so—time for the Army Corps of Engineers to blast and clear the series of rock pinnacles down river, near the town of Thebes, that threaten barges during this time of low water.
But sending out more water from the Missouri would doom states upstream, such as Montana, Nebraska, and South Dakota, which depend on water from the Missouri and are also caught in the drought.
"There are farmers and ranchers up there with livestock that don't have water to stay alive. They don't have enough fodder. They don't have enough irrigation water," said Robert Criss, a hydrologist at Washington University in St. Louis who has spent his career studying the Mississippi. "What a dumb way to use water during a drought."
Elected officials from South Dakota and elsewhere have pushed back strenuously at the idea of sending their water downstream. Foster reckons there is at best a 50-50 chance Obama will agree to open the gates.
But such short-term measures ignore an even bigger problem. Climate scientists believe the Mississippi and other rivers are headed for an era of extremes, because of climate change.
This time last year, the Mississippi around St. Louis was 20 feet deeper because of heavy rain. In the spring of 2011, the Army Corps of Engineers blew up two miles of levees to save the town of Cairo, Illinois, and Missouri farmland, and deliberately flood parts of rural Louisiana to make sure Baton Rouge and New Orleans stayed dry.
"It has kind of switched on us, and it switched pretty quick," said the Coast Guard chief Ryan Christiansen. "It wasn't that long ago that you had pretty high flooding, and now we are heading towards record lows."
Others argue that the Mississippi is already overengineered, after a century and a half of tampering with the river's natural flow.
Over the decades, Congress funded a number of projects to deepen the shipping channel, doubling it in depth to nine feet, and building an elaborate system of locks and dams to keep the river in a confined space.
The Army Corps of Engineers is constantly dredging the river's sandy bottom or building new levees to keep barges moving.
Those efforts to confine the river to a deep and narrow channel are believed to have made surrounding areas more vulnerable to extreme floods—like in 2011, when thousands were forced to flee their homes.
They may also not make sense in the long-term use of the river.
Criss argues the long barge trains floating on the Mississippi are just too big for the upper reaches of the river anyway, and that the industry is unfairly subsidized compared with other transport providers such as rail.
"The whole system around here has been entirely reconfigured to accommodate these monstrous barges," he said.
"This is the whole problem. We want to run boats on the river with nine-foot drafts that are almost a quarter of a mile long. They are too big for the size of the river up here."
The Mississippi, Criss said, needs smaller boats.
The Mississippi River has long been a flashpoint for climate change. Climate Desk has collected and mapped stories from our partners over the last several years; click on the map below to explore.