Colo. Rev. Stat. § 37-48-114
Before the Rio Grande water conservation district is established under this article, a petition shall be filed in the office of the clerk of the district court of the twelfth judicial district in and for Alamosa county, signed by not fewer than four hundred landowners, each of which owns eighty or more acres of land situated within the limits proposed to be organized into said district. The petition shall set forth the name of the proposed district and a general description of the boundaries of the proposed district and shall pray for an election on the question of organization of the proposed district. No petition with the requisite signatures shall be declared void on account of alleged defects, but the court may permit the petition to be amended at any time to conform to the facts by correcting any error. Similar petitions, except for signatures, may be filed and together shall be regarded as one petition. All such petitions filed prior to the hearing on the first petition filed shall be considered by the court the same as though filed with the first petition placed on file. In determining whether the requisite number of landowners have signed the petition, the court shall be governed by the names as they appear upon the tax roll. Duplicate copies of the petition covering the lands in each county shall be prepared and sent to the treasurer of each such county. Each treasurer shall examine the copy of such petition sent to him and shall file a certificate with said district court in and for Alamosa county stating as to each signatory whether such person owns eighty acres of land or more. Such certificate shall be prima facie evidence as to such ownership. For the purposes of this article, any person owning land in joint tenancy or as a tenant in common shall be deemed an owner of all land so held.
C.R.S. § 37-48-114