In the early 1990s, Carlos represented a municipality on the Colorado River in negotiations to secure the delivery of Colorado River water for municipal use. Because the municipality did not own the water system within its municipal boundaries, these negotiations involved not only the U.S. Bureau of Reclamation, but the local private water company.

In the Gila River Adjudication proceedings, Carlos also represented the City of Globe, Arizona, over whether it should be included as a party to the settlement of water rights claims asserted by an Indian tribe in eastern Arizona. While the U.S. Congress had enacted legislation to resolve the water rights claims of that Indian Tribe, the legislation incorporated by reference a settlement agreement that had not yet been finalized. After the legislation was passed, the settlement agreement was finalized but it excluded the City of Globe. In proceeding before the state superior court that administers the Gila River Stream Adjudication, he argued that this exclusion was contrary to the expressed intent of Congress that Globe be included in any settlement. The parties eventually were able to amend the settlement agreement to include Globe as a settling party.

For the City of Prescott, Carlos negotiated a complex agreement to share in the costs and management of a pipeline to import groundwater from a remote groundwater basin to Prescott and at least one other community.