For the purpose of removing snags, wrecks, and other obstructions in the Mississippi River, the Atchafalaya and Old Rivers from the junction with the Mississippi and Red Rivers down the Atchafalaya River as far down as Melville, Louisiana, the Secretary of the Army, upon the application of the Chief of Engineers, is authorized to draw his warrant or requisition from time to time upon the Secretary of the Treasury for such sums as may be necessary to do such work, not to exceed in the aggregate for each year the sum of $100,000.