Stream Connectivity Effects on Island Backchannel Habitat Conditions Under Regulated Flows in the Lower Osage River

The connectivity of backchannels to main channel flow in rivers, including flow regulated rivers, can affect backchannel habitat.  The purpose of this study was to determine the optimal flow ranges to increase habitat diversity and enhance dissolved oxygen (DO) in selected backchannels of the lower Osage River. Bagnell Dam on the Osage River uses hypolimnetic release for hydroelectric power generation, and the stage, temperature, and DO of the river can vary greatly on a daily basis due to changes in flow releases. Water released from the hypolimnion often has low DO during late summer and early fall, especially following high flow releases.  At low flow releases, many backchannels are disconnected from the main channel, creating lentic habitats that do not benefit from the enhanced DO of low releases. Modification of island backchannels to enhance connectivity with the main channel at low flow releases would cause backchannels to be lotic more often, and possibly enhance DO conditions.  Water temperature, DO levels, and flow rates were measured in the main channel and selected backchannels of the lower Osage River.  DO levels at different flows entering the backchannels were evaluated to determine optimal flow ranges to allow for habitat diversity and DO enhancement.