Augmentation plans in Colorado were established in the 1969 Water Rights Determination and Administration Act (“1969 Act”). The 1969 Act recognized the hydraulic interaction relationship between surface water rights and alluvial groundwater rights, and that groundwater rights that were generally junior to surface water rights could injure the senior rights, especially since at the time there was rapidly increasing alluvial well pumping. Therefore, one of the results of the 1969 Act was to require augmentation plans for junior water users on over-appropriated streams that would require these users to obtain sufficient replacement water to offset any injurious depletions to senior water rights. In this way, junior water rights could continue to pump as long as they didn’t injure the senior rights. Augmentation plans apply to any junior groundwater right, whether it is associated with an alluvial aquifer adjacent to a stream or not-nontributary water of the Denver Basin.
The inefficient water from lawn irrigation that makes it back to nearby streams is called a lawn irrigation return flow, or LIRF for short. Some municipalities have been claiming LIRF credits for over 30 years in Colorado, but many municipalities are not claiming this water to which they have a right.