When it shall become necessary to build any irrigation works or any portion thereof to supply water for the purpose of irrigating the lands of said irrigation district, the said board of irrigation commissioners shall advertise for sealed bids for the construction of the same by advertisement for three consecutive weeks in the official paper of the county in which said district is situated, and may give such other public notice as they may deem expedient and proper; and shall let the work of constructing the same to the lowest responsible bidder, and in letting said work they may let the whole of said work to any one party, or may let portions of said work to different parties.