Colo. Rev. Stat. § 37-86-112
If at any time any ditch or reservoir from which water is drawn for irrigation shall not be entitled to a full supply of water from the natural stream which supplies the same, the water actually received into and carried by such ditch, or held in such reservoir, shall be divided among all the consumers of water from such ditch or reservoir, as well as the owners, shareholders, or stockholders thereof, as the parties purchasing water therefrom and parties taking water partly under and by virtue of holding shares and partly by purchasing the same to each his share pro rata, according to the amount he is then entitled, so that all owners and purchasers shall suffer from the deficiency arising from the cause aforesaid each in proportion to the amount of water which he should have received in case no such deficiency of water had occurred.
C.R.S. § 37-86-112