If it be proposed by said petition to construct new works for the irrigation of said lands, or to purchase works only partially completed and not yet in operation, the petitioners must accompany the petition with a map of the proposed district. Said map shall show the location of the proposed canal or other works by means of which it is intended to irrigate the proposed district, and all the canals situated within the boundaries of the proposed district: provided, that canals that only pass through said lands and which do not in fact irrigate any of the same need not be shown. If said water supply be from natural streams, the flow of said stream or streams shall be stated in terms of cubic feet per second. If the water supply for said district is to be gathered by storage reservoirs, said map shall show the location of said proposed reservoirs, and shall give their capacity in acre feet. Said map shall be drawn to a scale of two (2) inches to the mile. Cross sections of the proposed canal, and all canals existing within the boundaries of said proposed district and shown on said map, and all proposed dams and embankments, shall be given in sufficient number to show the contemplated mode of construction, and the capacity shall be given in cubic feet per second of the proposed and said existing canals. Such cross sections shall be drawn to a scale of ten (10) feet to the inch, and said map and cross sections, together with an estimate of the cost of such works, shall be certified to by a well known and competent irrigation engineer.