CO SB074

Amends Colorado water law to define lawful maximum irrigated acreage for pre-1937 irrigation water right decrees that do not expressly limit the number of acres that may be irrigated, based on the maximum amount of acreage actually irrigated during the first 50 years after the decree was entered.

Allows acreage within reasonable proximity to the ditch (including extensions and lateral delivery infrastructure constructed within the first 50-year period) to be included in historical consumptive use analyses supporting water right change applications, even if acreage exceeds the original decree specifications.

Specifies that irrigation of acreage not exceeding the lawful maximum amount and located within reasonable proximity to constructed infrastructure is deemed lawful for continued irrigation under the water right in enforcement actions brought by the State Engineer or other parties.

Establishes that courts may only override these determinations through final judgment, preventing unilateral expansion of water rights beyond historically irrigated acreage.

Takes effect August 7, 2013, unless subject to a successful referendum petition, in which case it becomes effective only if approved by voters in the November 2014 general election.