Just weeks after high waters closed the Mississippi to cargo and recreational boats, low water is now causing problems. Weiss DeVos is chief of maintenance for the Army Corps of Engineers, and explains the flooding’s actually linked to waters that are so low this week, boats are running aground in the river channel. When water rises, the riverbottom rises — sediment fills the middle of the channel, and if the river drops slowly after a flood it cleans that out. But this spring the floods receded fast, the mud stayed in the river, and last week two shipping barges ran aground in St Paul, Minnesota. Today the river’s closed because a tugboat’s grounded in Hannibal, Missouri, and dredges must scoop out the riverbottom.He says it varies from year to year, and there are some “historic dredge cuts” where sandbars form a lot. DeVos says right now nothing’s going to the gulf via the Mississippi shipping route.The river by Hannibal must be reopened, and derrick boats as well as a hydraulic dredge are on the way to clean out the river. DeVos says there are several of those “historic” dredging sites where work’s planned for the river channel in Iowa, but that will be delayed by the work near Hannibal where sediment has closed the river to shipping.