A bill to amend the Act of December 22, 1944 (known as the "Flood Control Act 0f 1944") to mitigate damages resulting from water management decisions, and for other purposes.

Directs the Secretary of the Army, to the extent consistent with the Flood Control Act of 1944, to operate the Missouri River mainstem reservoirs to minimize adverse environmental and economic impacts to authorized uses on the Missouri River and reservoir system. Requires the Secretary, if an authorized use is threatened with adverse impact by the operation of the system, to implement operational changes to prevent or mitigate such impact unless the potential impacts of the preventive or mitigative action requested by the affected State or tribe outweigh the environmental and economic impacts.

Directs the Secretary to make grants to affected States or tribes for: (1) mitigating impacts in the system incurred as a result of implemented or denied operational adjustments; and (2) constructing specified facilities.

Authorizes appropriations.