In order to effectuate the policy declared in sections 701a and 701b of this title, and to correlate the program for the improvement of rivers and other waterways by the Department of the Army with the program for the improvement of watersheds by the Department of Agriculture, works of improvement for measures of run-off and water-flow retardation and soil-erosion prevention on the watersheds of waterways, for which works of improvement for the benefit of navigation and the control of destructive floodwaters and other provisions have been adopted and authorized to be prosecuted under the direction of the Secretary of the Army and supervision of the Chief of Engineers, are authorized to be prosecuted by the Department of Agriculture under the direction of the Secretary of Agriculture and in accordance with plans approved by him. The Secretary of Agriculture is authorized in his discretion to undertake such emergency measures for run-off retardation and soil-erosion prevention as may be needed to safeguard lives and property from floods and the products of erosion on any watershed whenever fire or any other natural element or force has caused a sudden impairment of that watershed: Provided, That not to exceed $300,000 out of any funds heretofore or hereafter appropriated for the prosecution by the Secretary of Agriculture of works of improvement or measures for run-off and water-flow retardation and soil-erosion prevention on watersheds may be expended during any one fiscal year for such emergency measures. For prosecuting said work and measures there is authorized to be appropriated the sum of $10,000,000 to be expended at the rate of $2,000,000 per annum during the five-year period ending June 30, 1944: Provided, That such works and measures which are herein authorized to be prosecuted by the Department of Agriculture may be carried out on the watersheds of the Rio Grande and Pecos Rivers subject to the proviso in section 701b of this title.