Arizona's Stream Adjudications

Certainty about water resources drives economic development and enables sustainable water management. Until claims in the adjudications are resolved, Arizona will not have the water certainty it needs to plan for the future.

“Surface water” is water flowing in streams, rivers, canyons and other natural channels above and below the ground.

In Arizona and many other western states, surface water rights have special attributes. One of the most important is priority: A person who first appropriates water from a stream has a water right that is higher priority than the rights of later appropriators. But that right is limited to the quantity regularly used, the location of diversion and the type of use that the water is put to.

This rule, known as the doctrine of prior appropriation, protects water users’ investments – for example, a farmer with a senior right does not have to worry that a new residential subdivision upstream will use up the water the farmer depends on. In addition, it provides certainty needed to plan for future supplies. And it gives every water user a better idea of the risks of future shortages.

But for prior appropriation to work, someone needs to define and catalog all of the surface water rights in the watershed, from most senior to most junior, along with their other attributes. A stream adjudication is the proceeding where this happens.

Cities, towns, tribes, farms, ranches, mines, national parks, state parks, homeowners and others all rely on surface water in these watersheds. Until the surface water rights in the Gila and Little Colorado watersheds are finally adjudicated, these water users will not have certainty about their water rights. This uncertainty makes it difficult to manage water supply sustainably or to plan for future water needs.  

Launched in 1974, the Gila Watershed adjudication will determine the surface water rights to Arizona’s Gila River and all its tributaries and sub-tributaries, including the Salt, Verde, San Pedro, San Francisco, San Simon, Santa Cruz, Agua Fria, and Hassayampa Rivers. There are 40,000 parties involved in the Gila River adjudication and about 85,000 claims.

The vast majority of claimants – around 92% of them – are asserting a right for less than 250 acre feet of water per year. These smaller claimants are looking for water for domestic use, irrigation or their stock ponds (used for watering livestock or wildlife).

The Little Colorado Watershed adjudication, which commenced in 1978, involves approximately 6,000 parties and 14,000 claims.

97% of the claims are for a water right less than 250 acre feet of water per year for domestic use, irrigation or a stock pond.

Notably, the Navajo Nation and Hopi Tribes are also parties to this proceeding.

It is tempting to simply shrug off the adjudications as proceedings that will never end – at least in our lifetimes. After all, they’ve already taken more than half a lifetime. But much has been accomplished in the adjudications.

The proceedings have given rise to numerous novel and complex questions of law. Initially, tribes challenged the state court’s jurisdiction to adjudicate their water rights, which are determined by federal – not state – law. The litigation over federal rights jurisdiction ended in decisions in the United States Supreme Court (1983) and the Arizona Supreme Court (1985) upholding the state court’s exercise of jurisdiction over the federal claims.

In 1989 the state court adopted a special procedure for reviewing substantial foundational issues in the Gila adjudication. Between 1990 and 2002,  the Arizona Court took review of six questions , each of which was argued and decided separately. Parties filed petitions for United States Supreme Court review of two of the decisions. (Both petitions were denied.) 

In 1995, the Legislature amended the state’s adjudication statutes, leading to years of litigation over the constitutionality of the amendments, finally terminating in 2000, when the Arizona Supreme Court  invalidated most of the amendments .

In the meantime, Arizona has finalized more  Indian water rights settlement agreements  than any other state. This is no small feat. When Indian reservations were created through treaties between tribes and the United States government, the intention was to enable tribal communities to become self-sufficient. Water is an essential resource for self-sufficiency. Accordingly, Indian tribes have a right to the water needed to become self-sufficient. However, tribes must prove up and quantify their water rights in stream adjudications and/or negotiated settlements. These settlements are complex agreements typically requiring an act of Congress, signed by the President.

“Under Arizona's bifurcated system of managing surface and groundwater, the concept of subflow serves to protect appropriable surface water rights against interference caused by the pumping of groundwater. Because water is a very precious and limited commodity in Arizona, much turns on how ‘subflow’ is determined.” Gila IV (2000)

In Arizona, within specially designated areas known as Active Management Areas and Irrigation Non-Expansion Areas, water withdrawn from wells is strictly regulated. Outside of those areas, well water is not regulated, and a land owner is free to drill a well and withdraw its water for almost any beneficial use. This rule comes into direct conflict with the doctrine of prior appropriation in places where wells may be withdrawing water that would otherwise be part of a river or stream’s sub-surface flow. Whether such well water is legally surface water or groundwater has been a major issue in the Gila adjudication.

In 2000, in a landmark opinion, the Arizona Supreme Court ruled that well water is surface water, subject to the rule of prior appropriation, if it is withdrawn from the hydro-geological zone called the “saturated subplain Holocene alluvium.” In the adjudications, this zone is referred to as the “subflow zone.” This includes wells that have created a cone of depression that draws water from the subflow zone.

The court charged the Arizona Department of Water Resources with identifying wells that may be pumping subflow. While this has proved a daunting task, requiring detailed hydrological analysis and entailing numerous legal challenges, the Department has completed the subflow delineation in the San Pedro Basin and has been directed to start work on the Verde Basin.

The Arizona Supreme Court’s subflow ruling means that some – possibly many – wells will be deemed to be withdrawing subflow. One might assume that the litigation over the subflow issue, which started in 1987, would have halted well development near rivers. Unfortunately, this has not been the case at all. In the years after the Supreme Court’s ruling on subflow, well development in such areas has continued – even increased.

The Verde Basin had around 7,450 wells in 1987. By the time the Supreme Court finally ruled on the issue, another 5,660 wells had been drilled. Since then, an additional 4,650 wells have been drilled. 

The Upper San Pedro Basin had around 3,600 wells when the subflow issue was first raised. By the year 2000, an additional 2,785 wells had been drilled. Since the Supreme Court clarified the law of subflow, almost 3,000 additional wells have been drilled.

These wells serve individuals, businesses and entire communities. Many of the water users who rely on these wells will be found to have surface water rights so junior that there will be no water available for them. 

“Until that process is complete, uncertainty regarding the nature, extent and priority of water rights will make it difficult to identify all the strategies necessary for meeting projected water demands.”

Likewise, in its 2019 report on  Long Term Water Augmentation Options for Arizona , the Governor’s Water Augmentation, Innovation and Conservation Council noted:

"Since the 1970s, development has increased reliance on this water, the combined claims to which exceed the available supply. Eventual resolution of the claims in court means some current water users may no longer be able to use this water. This uncertainty presents a significant barrier to planning for future water needs and long-term reliability and prevents water users from assessing water augmentation needs. These claims also include environmental and other interests seeking water for instream flows, the needs of which can be difficult to evaluate without adjudicated water rights."

Cities and towns seeking bond financing or businesses seeking loans may very well be told that they face too much water supply uncertainty to qualify.

In recent years, experts convened by the Kyl Center for Water Policy have conceptualized different ways of expediting the adjudications. Among the concepts discussed are grandfathering current well owners while limiting development of new wells, and establishing special markets for surface water rights. To implement such concepts would require strong local leadership and participation by a number of parties.

In the meantime, one way to keep the problem of reliance on subflow from growing is to provide current and future land-owners sufficient information to make informed decisions about reliance on well water.

In addition, the state should ensure that the adjudication court and the Arizona Department of Water Resources have sufficient personnel and other resources to complete the proceedings efficiently. With most of the major foundational issues out the way, greater investment in court and ADWR adjudication staffing and resources is merited and will hasten the adjudication process.