## Facts

- Fort Collins developed a Poudre River recreation corridor with parks, trails, and features intended to support recreation and fish and wildlife resources.
- Two structures in the corridor were central: the Nature Center Diversion Dam (used to redirect the river back to its historic channel after flooding) and the Power Plant Diversion Dam (renovated with a functional boat chute and fish ladder).
- On December 31, 1986, Fort Collins applied in Water Division 1 for conditional surface water rights in the Cache La Poudre River, claiming 55 cfs for municipal and recreational purposes and initially identifying the corridor as the diversion structure.
- Multiple entities, including Thornton, opposed the application.
- In 1988, after negotiations with state entities, Fort Collins amended the application to identify the Nature Dam and Power Dam (instead of the corridor) as the diversion structures.
- The water court awarded a conditional right for the Nature Dam, denied a conditional right for the Power Dam, and assigned an appropriation date (February 18, 1986) for the Nature Dam right.
- Thornton appealed (challenging relation-back and the appropriation date); Fort Collins cross-appealed (challenging denial of the Power Dam right and aspects of the appropriation-date analysis).

## Issues

1. Whether Fort Collins’ 1988 amendments substituting the Nature Dam and Power Dam as diversion structures related back to the 1986 application filing for priority and notice purposes.
2. Whether the evidence supported the appropriation date assigned to the Nature Dam conditional right under Colorado’s “first step” requirement for appropriation.
3. Whether the Nature Dam and the Power Dam qualified as diversion structures capable of supporting conditional surface water rights for municipal, recreational, and related beneficial uses.

## Decision

- The court held that the 1988 amendments related back to the 1986 filing because the source, amount, and general uses remained consistent and the original filing provided adequate notice.
- The court affirmed that the Nature Dam could constitute a valid diversion, but reversed the appropriation-date determination and remanded for additional findings.
- The court reversed the denial of a conditional right for the Power Dam, holding that the renovated boat chute and fish ladder could constitute structures that control water, and remanded for further proceedings on beneficial use and other requirements.
- Disposition: Thornton’s appeal was affirmed in part and reversed in part with remand; Fort Collins’ cross-appeal was reversed with remand.

## Legal Principles

- An amendment to a water-right application may relate back to the original filing date when the original application gives adequate notice by identifying the same source, amount, and general uses; refinement of diversion-structure identification does not necessarily defeat relation-back.
- A conditional water right requires an appropriation intent plus an overt act (“first step”) toward diversion and application to beneficial use; adoption of a planning document, standing alone, is insufficient to fix an appropriation date.
- “Diversion” is not limited to traditional off-channel withdrawal; a physical structure that controls or directs streamflow can satisfy the diversion element when tied to recognized beneficial uses.
- Recreational and environmental purposes (including boating features and fish passage/habitat protection) can qualify as beneficial uses if the claimant proves actual control of water and application consistent with the statutory scheme.

## Conclusion

The court allowed Fort Collins’ amended conditional-right claims to relate back to the original filing, required a renewed appropriation-date analysis because planning alone did not establish the “first step,” and recognized that structures controlling in-stream flows for recreation and habitat may satisfy the diversion requirement, remanding for further findings on both dams’ rights.


City of Thornton v. City of Fort Collins, 830 P.2d 915 (Colo. 1992)