The adjudication of water rights in the Gila River basin in Arizona is arguably the most complex piece of litigation in the history of the United States. The adjudication is over forty years old. Today, there are over 38,000 parties with nearly 100,000 claims. At stake in the case is the sustainability and productivity of a river basin that includes critical habitat and endangered species, scarce water supplies for desert communities, farms, and industries, and sacred resources for indigenous peoples. While there are many obstacles preventing an expeditious resolution of the Gila River general stream adjudication, some of the most significant obstacles are presented by the United States Constitution and the Constitution of the State of Arizona. This Article describes the Gila River Adjudication, discusses the potential constitutional obstacles to its resolution, and proposes reforms that could serve to overcome or mitigate those constitutional obstacles.

The words “Arizona” and “progressive” are seldom used in the same sentence but, when it comes to water, Arizona has a distinguished record of innovation in water law and policy. This article explores novel solutions to water shortages recently developed by Arizona water lawyers and managers. It draws on presentations at an Arizona Water Law conference hosted by the Arizona College of Law Rogers College of Law in December 2017. The recurring tool is water exchanges, that is, the substitution of one type of water for another, such as Colorado River water delivered through the Central Arizona Project for groundwater. Exchanges have become a reliable and valuable tool to solve seemingly intractable engineering challenges. Lest I be perceived as simply a shill for my adopted State, I’ll also critique some foibles and missteps in water management. Arizona water managers are chasing a rainbow in pursuing “augmentation” in the form of desalination from ocean water off the coast of California or Mexico.

The Colorado River provides water to over 40 million people and to nearly 5.5 million acres of farmland in seven states, and more than 4,200 megawatts of electrical generating capacity from hydroelectric facilities, before providing water to approximately 2.8 million people in Mexico and irrigating around 207,000 hectares (over 511,000 acres). The river is vital to the economies of the southwestern United States and Mexico and has become one of the most regulated and managed rivers in the United States. The Colorado River Basin is divided into two basins: the Upper Basin (consisting of areas of Arizona, Colorado, New Mexico, Utah, and Wyoming) and the Lower Basin (consisting of areas of Arizona, California, and Nevada). The Colorado River was allocated in the first half of the twentieth century, during one of the highest-flow periods in its known history. Since that time, it has become apparent that the Colorado River is overallocated. Additionally, the River is a highly variable system, subject to dramatic change in runoff from year to year. Based on tree ring studies, the period from 2000 to 2015 ranks as the fifth driest 16-year period in the last 1,200 years. Recognizing the gravity of the situation, representatives from the Lower Basin States and the Bureau of Reclamation (Reclamation) have been working on plans to avoid and mitigate shortage since the early 2000s. Although the 2007 Interim Guidelines helped to coordinate operations of Lake Powell and Lake Mead and provided tools to conserve and augment supplies on the river, by 2013 there was broad recognition additional work remained to be done. Due to the junior priority of much of its Colorado River allocation, Arizona has been preparing for shortages for decades. For many Arizona users, the greater threat has been deeper shortages that could be catastrophic. The Colorado River supplies approximately 38% of Arizona’s water needs. If a shortage is declared on the Colorado River, Arizona bears the brunt of the reductions, with the Central Arizona Project (CAP) water users taking most of the reductions. Collective efforts to conserve water in Lake Mead have been hugely successful and have been instrumental in avoiding shortages since 2015. The proposed Lower Basin Drought Contingency Plan (LBDCP) would continue these conservation efforts through additional reductions to all three Lower Basin States, along with conservation by Reclamation, into 2026, with a goal of reducing the risk of Lake Mead elevation falling to 1020 feet. Mexico has already agreed to participate in corresponding additional reductions, should the LBDCP become effective in the U.S.13 Arizona’s future, economic and otherwise, depends on the ability of its water users to come together and agree to the LBDCP through one voice.

A Colorado River shortage is coming. The exchange program between Phoenix and Tucson-area subcontractors is an elegantly simple solution to protect against a municipal shortage because it takes advantage of preexisting legal frameworks and fills capacity in already-built infrastructure. Surface-water dependent Phoenix delivers Central Arizona Project (CAP) water it cannot presently use to recharge facilities that the groundwater-based Tucson area does not presently need to fill. As noted below, the current Tucson/Phoenix exchange is both an intergovernmental agreement (IGA) between Tucson and Phoenix, and a pilot project between Tucson, Phoenix, and the Metropolitan Domestic Water Improvement District (Metro). It could readily morph into a series of exchange agreements between additional Tucson area parties and MetroPhoenix area parties, as well. At the largest scale, the “Tucson/Phoenix exchange” means using Southern Arizona’s productive, and clean aquifers—and more precisely, the large amount of clean storage space in the vadose zone above those aquifers—to store water for the Phoenix area. During an “exchange,” the Tucson area would pump stored water and place an order to have Tucson-area CAP water directly delivered to Valley-area water treatment plants. But even this simple solution has taken at least 5 years to implement; and due to a variety of administrative challenges, Tucson has yet to deliver water to Phoenix, even on a “pilot scale.” Flexibility, collaboration, innovation, and creativity will become increasingly necessary to meet Arizona’s water needs; the Tucson/Phoenix exchange shows a pathway that—now that it has been almost completely invented, revised, collaborated, dissected, permitted, and approved—is ready to be a substantial component of Arizona’s shortage implementation strategy.