Colo. Rev. Stat. § 37-84-110
Every corporation and company, whether created by special act or organized under the general incorporation laws of this state, and every partnership or any persons who own or control any canal or ditch, or any part thereof, being two feet in width or over and carrying water to the depth of twelve inches or over, which canal or ditch, or any part thereof, is within the corporate limits of any city with a population of seventy thousand or more or any city existing by special charter of a population equal to or exceeding seventy thousand, or any of the additions thereto, at their own expense, shall safely and securely lattice or slat the head of any flume or covering of the canal or ditch with proper materials, so that persons or animals cannot accidentally enter such flume or covering at the head thereof and pass or be carried down the current of the canal or ditch, and they shall thereafter maintain and keep the same in good order and repair at their own cost and expense.
C.R.S. § 37-84-110