Colo. Rev. Stat. § 37-84-113
The owners of any irrigation ditch, canal, or reservoir, transferring water from one natural stream to another, or from a reservoir, ditch, or flume to a stream in order that said water may be diverted from such stream for irrigation or any other purpose, shall construct suitable and proper measuring flumes or weirs, equipped with self-registering devices if required by the state engineer, for the proper and accurate determination of the amount and flow of water turned into, carried through, and diverted out of said natural stream. If the owners of any such irrigation ditch, canal, or reservoir fail or neglect, upon five days' previous notice in writing duly served upon them or their agent or employee, to erect, maintain, or repair such measuring flume, weir, or device, the state engineer or division engineer shall refuse to allow to be taken or diverted from any stream any water whatever on account of delivery of water to such stream, for such time and until such owners cause to be erected or repaired such flumes, weirs, or devices, at the point of delivery to and taking from said natural streams so used as a conduit.
C.R.S. § 37-84-113