On May 9, 2012, the Army Corps of Engineers will cut the discharge rate from Gavin’s Point Dam to zero, yes zero.  That means no water will exit through the structure’s power tunnels or spillway gates.  The Army must stop the flow of water through the dam in order to inspect it for any damages.  Last year, the Missouri’s powerful floodwaters pounded the structure, especially its spillway.  The Army wants to know just what the Missouri did to the dam. Without water pouring through Gavin’s Point Dam, the Missouri downstream through southeastern South Dakota and western Iowa will drop to a record low level.  It remains to be seen just how low the Missouri will go.  Much depends on tributary inflows.  If the James and Big Sioux rivers do not dump large volumes of rainwater into the Missouri, we can expect the river at Sioux City to diminish to a trickle.  We do know that during the eight hours the Army pinches off the river’s flow, the Missouri will drop to one of its lowest levels ever, possibly lower than at any time since the glacial formation of the stream 30,000 years ago. Continue Reading »