Civ. Code, § 1422

If the place of intended diversion or any part of the route of intended conveyance of water so claimed, be within, and a part of, any national park, forest reservation, or other public reservation, and be so shown in the notice of appropriation of said water, then the claimant shall have sixty days, after the grant of authority to occupy and use such park or reservation for such intended purpose, within which to commence the excavation or construction of said works; provided that within sixty days after the posting of said notice of appropriation, as provided in section 1415 of the Civil Code, the claimant shall in good faith commence (and thereafter diligently and continuously, except when temporarily interrupted by snow or rain, prosecute to completion) such surveys and other work as under the regulations governing such park or reservations, may be required as preliminary to, or for use with, an application for such authority; and provided also that the claimant shall in good faith on completion of said survey and preliminary work, apply to the officer, board, or body, having charge of such park or reservation, for such authority, and shall thereafter, prosecute said application with reasonable diligence.