Planning & Decision Process
Interactive Map

Problem Statement Objective

In the U.S. Supreme Court litigation Arizona v California, 376 U.S. 340 (1964), the State of New Mexico presented evidence of present and past uses of water from its tributaries in the Lower Colorado River Basin including the Gila River and its tributaries.  In addition, New Mexico presented a water supply study showing how the state could apply and use the water it claimed as its equitable share of the Gila River (Figure 1). In the resulting report of the Special Master, it was found that New Mexico should be allowed present uses as an equitable apportionment of the waters of the Gila River Basin, but did not make an apportionment of water to New Mexico to provide for future uses from the Gila.

Subsequently, the 1968 Colorado River Basin Project Act, P.L. 90-537, which authorized the building of the Central Arizona Project (CAP) included allocation of 18,000 acre-feet of water to New Mexico. This water is in addition to the water awarded in the 1964 court decree (30,000 acre-feet of consumptive use per year). The allocation was effected through an exchange by the Secretary of the Interior of 18,000 acre feet of CAP water for an equal amount of diversions of Gila River Basin water. However, the 1968 Act did not provide a means for New Mexico to divert the Gila water without objection by senior downstream users. The 2004 Arizona Water Settlements Act amends the 1968 Act and together with the Consumptive Use and Forbearance Agreement (CUFA), provides both the ability to divert without objection by downstream parties and the funding to help. The CUFA sets forth the rights and responsibilities of all involved parties. The CUFA also describes the terms and parameters under which diversions by New Mexico may occur without objection by the downstream parties, because additional diversions in New Mexico will be junior to all Gila rights existing as of September 30, 1968. It also describes how the Secretary of Interior will exchange CAP water for Gila basin water and how disputes may be resolved.

Specifically, the 2004 Arizona Water Settlements Act provides New Mexico 140,000 acre feet of additional depletions from the Gila Basin in New Mexico in any ten year period. In addition, the State of New Mexico will receive $66M for “paying costs of water utilization alternatives to meet water supply demands in the Southwest Water Planning Region of New Mexico, as determined by the New Mexico Interstate Stream Commission (NMISC) in consultation with the Southwest Water Planning Group (SWPG). Funds may be used to cover costs of an actual water supply project, environmental mitigation, or restoration activities associated with or necessary for the project. Further, if New Mexico decides to build a project to divert Gila basin water in exchange for CAP water, the state will have access to an additional $34-$62 million. According to the settlement, New Mexico has until 2014 to notify the Secretary of the Interior about plans to divert water from the Gila River.

Environmentalists have kept a wary eye on the negotiations due to concerns about possible environmental costs if New Mexico were to develop its entitlement to the Gila River, the last main stem river in New Mexico without a major water development project. They argue that whatever diversion technique is adopted will reduce water available for wildlife, vegetation, nutrient cycling and other vital river functions. The 2004 Act requires that the NEPA process must be completed with a record of decision by 2019. The legislation designates the U.S. Bureau of Reclamation as the lead federal action agency and provides that the State of New Mexico through the Interstate Stream Commission may elect to serve as joint lead. As such the Bureau (and NMISC) will plan the formal environmental compliance activities (e.g., NEPA).

In response, the NMISC, the Office of the Governor of the state of New Mexico, and SWPG have both adopted policies that “recognize the unique and valuable ecology of the Gila Basin.” In considering any proposal for water utilization under Section 212 of the Arizona Water Settlements Act, the NMISC will apply "the best available science to fully assess and mitigate the ecological impacts on Southwest New Mexico, the Gila River, its tributaries and associated riparian corridors, while also considering the historic uses of and future demands for water in the basin and the traditions, cultures and customs affecting those uses."

Now with the necessary settlements in place, decisions are needed as to how best to use the additional 140,000 acre feet of Gila water and the available funding, all before the applicable time limits expire. Ultimately, the NMISC will make that determination in consultation with the SWPG, the citizens of Southwest New Mexico and other affected interests. The New Mexico Interstate Stream Commission has committed to a continuing process of public information and comment to help arrive at such determinations.

Gila Basin Task Force:
Contributed by ISC

The web content contained herein focuses exclusively on the collaborative decision support modeling aspects of the program. Additional details on the broader aspects of the Gila Basin Task Force can be found at the New Mexico Interstate Stream Commission web site.