Integrating Canons of Construction into Western Tribal Water Rights Quantification

The standards used for the quantification of tribal water rights have substantial implications for resource equity and access on Native American reservations. Ever since the McCarran Amendment, 43 U.S.C. § 666 (1952), allowed states to join tribal and federal governments in water rights disputes in state court, states have taken radically different approaches to quantifying tribal water rights. Two standards for quantification predominate in the American West: the practically irrigable acreage (PIA) standard and the tribal homeland standard. The PIA standard embraces the assimilative agricultural purpose Congress had in mind when creating reservations and quantifies water rights based on the water needed to irrigate “practically irrigable acreage.” Elizabeth Weldon, Practically Irrigable Acreage Standard: A Poor Partner for the West's Water Future, 25 William & Mary L. & Pol’y Rev. 203, 205–06 (2000). By contrast, the homeland standard as theorized by Arizona courts considers several factors, like geography, topography, natural resources including groundwater availability, tribal and reservation history, and current and projected future water use. 989 P. 2d 739, ¶ 41–49 (Az. Sup. Ct. 1999) (hereinafter Gila River III). Neither standard truly fulfills the U.S. trust obligation to tribes, unless the Marshall-Cohen canons of construction, which instruct courts to “construe [statutes, agreements, orders, and treaties] liberally in favor of establishing Indian rights” are employed by state courts to give tribes the benefit of the quantification methodology that results in the greatest water right. See Felix S. Cohen’s Handbook of Federal Indian Law, Ch. 3 § C2b (2) (Strickland et al., eds. 1982). 

The PIA standard only accounts for the practically irrigable acreage on a reservation, which in many cases has little to do with how a tribe plans to use the water rights they perfect. This can result in alternative means of appropriations intended by the tribe, like instream flows, being limited as they were in Big Horn III. 835 P.2d 273, 279 (Wyo. 1992). And if a tribe is primarily located in a difficult to irrigate region, like the dry and high-elevation steppes of the Navajo Nation, the PIA standard may threaten tribal capacity to obtain sufficient water for their population. However, the PIA standard does offer tribes a measurable and predictable standard for quantification that a court can’t use to shortchange easily irrigable Native nations.

By contrast, the Arizona homeland standard accounts for a range of factors that more accurately match the uses that many non-agricultural tribes plan for their water. Theoretically, this makes the homeland standard a superior means for quantification. However, the standard considers data like current and future projected population and water needs. Gila River III. Most reservations are not densely populated spaces, a consequence of centuries of genocide and relatively recent federally supported relocation programs displacing Indigenous peoples into cities, boarding schools, and adoptive families. See C. Matthew Snipp, The Size and Distribution of the American Indian Population: Fertility, Mortality, Migration, and Residence (1996). These factors threaten to constrain tribal access to water based on current and immediately projectable conditions.

It is not a given that a rural tribe without substantial social infrastructure will be able to show that its projected future on-reservation population will increase rather than decrease. This is a potential consequence of job concentration in urban spaces, closed tribal membership rolls temporarily foreclosing future enrollment, and policies like the blood quantum, which constrain population growth in smaller tribes unable to sustain in-marriage. Without policy change, a tribe with high blood quantum requirements or closed rolls may have zero tribal members if those policies and enrollment trends are projected forward in time for another century. It is self-evident that no tribe concerned about their own survivance actually intends to take the course of self-elimination, but how would a court using a homeland standard project the future water needs of a tribe with closed rolls? Would the number be drawn towards zero-acre feet if there’s a projected population of zero in a hundred years? A court can’t guess what policy changes a tribe may make. Consequently, calculating tribal water rights with the homeland standard for a small tribe whose population is not currently on the upswing is likely to shortchange that tribe and limit any future growth to its current conditions and trends if insufficient water is available for future population growth on the reservation. This is not a concern with the practically irrigable acreage standard, which does not permit the court to call into question the viability of the reservation community’s population, although that standard is less than helpful when the tribe’s land isn’t easily irrigable.

There remains a potential stop-gap solution that can be employed by courts, and which is consistent with precedent. Central to the Marshall-Cohen model of federal Indian law are the Indian law canons of construction, which include the principle that the predatory treaties (as well as relevant statutes, agreements, and executive orders) that the United States signed with tribes should be construed as Indian signatories would have understood them at signing. This principle is embodied in the foundational water law opinion, United States v. Winans, 198 U.S. 371, 371 (1905), which interprets the Yakima treaty with Washington State (Treaty of 1859) “as they [the Indians] understood it and as justice and reason demand.” The Winans case is a touchstone for water law jurisprudence, and lingering questions of quantification methodology can be answered by the Indian law canon of construction around which Justice McKenna structures his seminal opinion. Tribal water rights are ultimately a question of treaty interpretation, and in Indian treaty interpretation this canon of construction prevails. Therefore, courts should adopt whichever means of quantification, PIA or homeland standard, that affords tribes superior water rights.

As a practical consequence of the perils of both means of quantification, tribes in states without a well-established jurisprudence surrounding quantification shoulder the burden of doing in-house calculations of both PIA and homeland quantifications before deciding which standard to pursue in litigation. But courts would do their part to best serve the interests of justice by elevating whichever standard would provide the tribe with greater water rights, as the greater quantification should be considered in line with established canons of Indian treaty interpretation. This historically conscious and precedentially sound approach may help to limit the risks of tribal water rights quantification and close the gap in water access for many reservation communities.