## Facts

- The Agua Caliente Band of Cahuilla Indians occupies a reservation in the arid Coachella Valley, where groundwater from the Coachella Valley aquifer is the primary water source.
- Federal executive orders in 1876 and 1877 withdrew lands to establish the reservation as a “permanent home” for the Tribe.
- Local water agencies (Coachella Valley Water District and Desert Water Agency) pump and manage water from the aquifer underlying the reservation and surrounding areas.
- The Tribe alleged the aquifer was being overdrafted and that pumping and recharge practices were degrading groundwater quality (including increased salinity).
- The Tribe sued for declaratory and injunctive relief, asserting a federal reserved right to groundwater under the Winters doctrine; the United States intervened as trustee for the Tribe.
- The litigation was divided into phases; Phase I addressed only whether the Tribe possesses a federal reserved right to groundwater.
- On cross-motions for partial summary judgment, the district court held the reservation’s creation impliedly reserved appurtenant water sources, including groundwater.
- The water agencies took an interlocutory appeal challenging that Phase I ruling.

## Issues

1. Whether the federal reserved rights doctrine (Winters) can apply to groundwater.
2. Whether establishment of the Agua Caliente Reservation impliedly reserved groundwater as part of the Tribe’s federal reserved water rights.
3. Whether state-law water rights and entitlements preclude or limit a federal reserved right to groundwater.

## Decision

- The Ninth Circuit affirmed the district court’s partial summary judgment for the Tribe and the United States.
- The court held that Winters reserved rights may include groundwater when needed to accomplish the reservation’s purposes.
- The court held that creating the reservation as a permanent homeland in an arid region impliedly reserved appurtenant groundwater in the Coachella Valley aquifer.
- The court held that the Tribe’s reserved groundwater right is not defeated by lack of historical groundwater pumping.
- The court held that conflicting state-law water rights are preempted to the extent they interfere with the federal reserved right.
- The court limited its ruling to the existence of a reserved right to groundwater, leaving quantification and water-quality or management remedies to later phases.

## Legal Principles

- When the United States reserves land for a federal purpose, it impliedly reserves sufficient water to fulfill that purpose (Winters reserved rights).
- Reserved water rights are defined by the purpose of the reservation and may extend to appurtenant water sources, including groundwater.
- No categorical rule limits federal reserved water rights to surface water; groundwater may be included where necessary to make the reserved land a viable homeland.
- Reserved rights arise at the time the reservation is created and are not lost by nonuse; they are not dependent on historical extraction methods or patterns.
- State water law and state-granted entitlements cannot defeat federal reserved rights and are preempted to the extent of conflict.

## Conclusion

The Ninth Circuit recognized that the Agua Caliente Band holds a federal reserved right to groundwater in the aquifer appurtenant to its reservation because groundwater is necessary to fulfill the reservation’s purpose as a permanent homeland, and conflicting state-law entitlements cannot displace that federal right.


Agua Caliente Band of Cahuilla Indians v. Coachella Valley Water Dist., 849 F.3d 1262 (9th Cir. 2017)