San Antonio v. Special Improvement District No. 1 of Rio Grande Water Conservation District, 270 P.3d 927

This case involves two consolidatedきwater cases challenging Special Improvement District No. 1’s (the Subdistrict) water management Plan in the San Luis Valley under SB 04-222 and related Colorado statutes.
The Plan seeks sustainable aquifer levels in the San Luis Valley while preventing material injury to senior surface-water rights, using a ground water management plan component within the Subdistrict’s official Plan.
The State Engineer approved the ground water management plan and the District/Trial Court approved the amended Plan with decree conditions and retained jurisdiction to ensure ongoing compliance.
The Plan relies on the Rio Grande Decision Support System (RGDSS) model and its response functions to project injurious stream depletions and to guide an annual replacement plan for replacement water.
Objectors argue the Plan improperly substitutes an augmentation-style review and lacks sufficient no-injury findings and enforceable safeguards; the court ultimately affirms the Plan as decreed as compliant with applicable statutes.
Key features include mechanism for surface water credits, CREP land retirement incentives, a replacement water framework, and authority for contracting with non-Subdistrict wells under future rules with public notice and judicial oversight.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Does the Subdistrict Plan meet statutory criteria for approval?	Objectors say Plan lacks no-injury threshold.	State Engineer and court found comprehensive, detailed, and aligned with SB 04-222.	Yes; Plan complies with the special statutory criteria.
Does the State Engineer have authority to approve annual replacement plans?	Objectors claim authority lies only with the water court.	Statute authorizes Engineer to approve replacement plans and regulate water distribution.	Yes; Engineer authority affirmed.
Can the water court impose decree conditions and retained jurisdiction for operation of the Plan?	Objectors contend court lacks authority to add conditions.	Statutes authorize retained jurisdiction to ensure plan operates to prevent injury.	Yes; court retained jurisdiction and decree conditions are valid.
Is use of phreatophyte effects as a credit permissible under 37-92-501(4)?	Shelton Farms/related doctrine bars credits for phreatophyte savings.	Model can account for evapotranspiration fluctuations; not prohibited.	Permissible to include modeling of ET fluctuations; not a prohibited credit.
May subdistrict contract with outside-wells to replace depletions under future rules?	Plan insufficiently contemplates inclusion of non-Subdistrict wells.	Legislation allows contractual arrangements and phased inclusion with safeguards.	Yes; contracts with outside wells permitted under conditions and notice.

Empire Lodge Homeowners' Ass'n v. Moyer, 39 P.3d 1139 (Colo. 2001) (basics of public resource, priority administration, and injury)
Cotton Creek Circles, LLC v. Bijou Irrigation Co., 181 P.3d 252 (Colo. 2008) (RGDSS and groundwater/surface water interaction guidance)
City of Aurora ex rel. Util. Enter. v. Colo. State Eng'r, 105 P.3d 595 (Colo. 2005) (specificity and non-injury standards in augmentation context)
Buffalo Park Dev. Co. v. Mountain Mut. Reservoir Co., 195 P.3d 674 (Colo. 2008) (requirement of specificity for non-injury in augmentation)
Eagle Peak Farms, Ltd. v. Colo. Ground Water Comm'n, 919 P.2d 212 (Colo. 1996) (reasonableness standard for quasi-legislative action and review)
V Bar Ranch, LLC v. Cotten, 233 P.3d 1200 (Colo. 2010) (State Engineer authority to regulate and investigate water matters)
Shelton Farms, Inc. v. Colo. Water Conserv. Dist., 187 Colo. 181, 529 P.2d 1321 (Colo. 1974) (phreatophyte considerations and replacement water credits under Shelton Farms)
Alamosa-La Jara Water Users Protection Ass'n v. Gould, 674 P.2d 914 (Colo. 1983) (historic conjunctive use and aquifer protection principles)