The surveys of navigable streams shall include such stream-flow measurements and other investigations of the watersheds as may be necessary for preparation of plans of improvement and a proper consideration of all uses of the stream affecting navigation, and whenever necessary similar investigations may be made in connection with all navigable streams under improvement. Whenever permission for the construction of dams in navigable streams is granted, or is under consideration by Congress, such surveys and investigations of the sections of the streams affected may be made as are necessary to secure conformity with rational plans for the improvement of the streams for navigation.
33 U.S. Code § 546 - Investigation of stream flow and watersheds; surveys in connection with dams
(June 25, 1910, ch. 382, § 3, 36 Stat. 669.)
Section is from section 3 of act June 25, 1910, popularly known as the “Rivers and Harbors Appropriation Act of 1910”. Other provisions of such section were omitted, as superseded by section 545 of this title.