Managing the Santa Cruz River: Prospects for a Future Binational Minute

Abstract

This paper examines the prospects for developing and implementing a binational water management agreement for the transboundary Santa Cruz River that crosses the US–Mexico boundary near the sister cities of Nogales, Sonora–Nogales, Arizona. After considering the geography, history, socio-economic context, and binational agreements affecting utilization of the Santa Cruz River, we review the conditions influencing recent binational progress on another transboundary river, the Tijuana River. Specifically, we ask what conditions created a favorable environment in which a binational agreement for management of the Tijuana River Watershed (TRW) was developed, what specific actions by relevant policy officials took place, and how the final agreement was reached. We then compare the dynamics that unfolded in the TRW with conditions in the Santa Cruz River to identify obstacles hindering progress towards achieving an International Boundary and Water Commission (IBWC) agreement (Minute) on shared management of the Santa Cruz River in its international reach. We find that the required political conditions that favored an agreement on the Tijuana River are not yet met on the Santa Cruz, although several favorable conditions do exist. We conclude with an assessment of current prospects for advancing binational cooperation that can inform discussion of how an IBWC Minute could be drafted to address water resource management issues in the Santa Cruz River Basin.

1. Introduction

Among the unapportioned rivers and streams that cross the U.S.–Mexico boundary, the Santa Cruz River (SCR) that links Arizona and Sonora is distinctive for its configuration, urban significance, and vital role in sustaining a badly impacted transboundary ecosystem. The SCR is one of those rare streams that crosses the international boundary twice, once near its headwaters in the San Rafael Valley near the Arizona community of Lochiel where it winds its way south into Mexico, and the second time just east of the twin cities of Nogales, Sonora and Nogales, Arizona (Ambos Nogales) where it re-enters the United States [1]. Along its course, the SCR sustains ranches and agriculture and serves as the primary water source for the rapidly growing Ambos Nogales binational metropolitan zone that is served by wells exploiting the SCR aquifer. As it passes the boundary from Nogales Sonora north in the US, the surface flow is nearly depleted. The SCR is replenished ten miles north by discharges from the Nogales International Wastewater Treatment Plant (NIWTP) that processes wastewater generated in the Ambos Nogales urban region and drainage from its tributary stream, Nogales Wash, that runs northward through the center of the twin cities. This treated effluent, in turn, waters a rich riparian ecosystem for nearly 30 miles north of the NIWTP where the river once again vanishes into the streambed, depleted by the intensive needs of farms, mines, and urban sprawl that stretch south from Tucson, Arizona.

The multiple challenges confronting the sustainable utilization of this important transboundary resource have long drawn the attention of the International Boundary and Water Commission (IBWC), both as regards sanitation and water quality issues, more recently on the interactions of surface water flows and regional groundwater. To date, only a limited number of formal agreements, all pertaining to sanitation, have been struck, and no agreements have been reached between the U.S. and Mexico on regional groundwater resources in the Ambos Nogales region [2]. Recent progress on transboundary watershed management elsewhere along the boundary suggests that more might be conducted to strengthen binational management for the SCR [3].

Accordingly, this paper explores the challenges and opportunities for advancing binational management of the SCR. As a point of reference, it draws on recent experience on the Tijuana River for evidence of a successful initiative advancing binational cooperation on that shared watercourse that may hold lessons for those who wish to strengthen cooperative measures for managing the transboundary reach of the SCR watershed [4,5].

2. Methods

This study adopts a qualitative research methodology [6], drawing on governmental, scholarly, journalistic, and non-governmental organization sources describing recent management of the Santa Cruz River. The principal analytic is comparative, juxtaposing political and advocacy conditions in the Santa Cruz River transboundary region with those associated with successful advocacy for a transboundary management agreement on the Tijuana River linking Baja California and California. We note that our study digs deeply into the sources noted above with a critical and objective eye, and we also acknowledge the limits of this approach in comparison to a thorough field-based effort. We nonetheless see the outcomes of our research shedding light on what variables and processes have been successful in the Tijuana River Basin and how this work can inform efforts to meet the challenges that the SCR faces.

The paper proceeds in five parts. We first explore the institutional context of binational watershed management, then present the relevant history and socio-economic context affecting water use in the SCR system. We then look at the institutional context and past binational agreements shaping current binational engagement in SCR management. With this context in mind, we examine recent progress on the Tijuana River for evidence of factors that facilitated the achievement of a binational watershed management effort, capped by an IBWC agreement, Minute 320, in 2015. We then look at the current array of conditions that are either conducive or non-conducive to strengthening binational cooperation that addresses the range of problems now afflicting the SCR watershed. We conclude with an assessment of current prospects for advancing binational cooperation on this important transboundary river.

3. Institutional Context of Binational Basin Research

Before we explore the regional context of the Santa Cruz River Basin, we discuss some selected research into water resource management in transboundary basins. Wilder et al. advanced the framework of hydro-diplomacy, a combination of water diplomacy and science diplomacy that draws on key elements of each frame to yield an adaptative water management approach to transboundary watershed management on the US–Mexico border. Key elements in this approach are social learning and relationships that are stable over time, governance mechanisms that are flexible, and strong networks of relevant, regional, governmental, and non-governmental stakeholders. This research also notes the need for a strong institutional framework, within which discussions towards successful binational watershed management can occur [7].

The U.S.–Canada border region offers an especially relevant case of transboundary watershed management that informs our work. The International Joint Commission (IJC) is a binational management framework that has supported collaborative water resource management between the U.S. and Canada since the signing of the 1909 Boundary Waters Treaty to resolve transboundary watershed issues on the St. Mary and Milk Rivers that flow between Montana and Alberta [8]. Of note to this paper is the International Watersheds Initiative that was developed by the IJC in 1998 to deploy an ecosystems approach to integrated water resource management in transboundary US–Canada watersheds. Key elements to the IWI that inform our work include the concept of parity between the U.S. and Canada, and the inclusion of local knowledge and public participation in binational negotiations [9].

The literature reviewed above notes that successful transboundary watershed management relies on a solid institutional framework, the inclusion of key local players and knowledge, active engagement of members of the public, and a flexible framework for discussion of issues of relevance to parties interested in the management of these watersheds. We now turn to discussion of the regional context of the Santa Cruz River Watershed and explore the degree to which the elements noted above may be relevant to this binational basin.

4. Regional Context of the Santa Cruz River Basin

As commentators note, the SCR is the principal all-season water-source for a semi-arid grassland and montane region spanning the international boundary that includes Lochiel, Ambos Nogales, Rio Rico, and other communities farther north, including Tucson, that historically relied on its waters [10]. The growth of Ambos Nogales, the principal port-of-entry on the Arizona–Sonora boundary, drove rising demand on SCR waters after World War II as the Nogales POE became the passage for agricultural products flowing out of Sinaloa and Sonora to US winter fruits and vegetables markets. The emergence of assembly for export manufacturing with the Border Industrialization Program (BIP) after 1965 [11] propelled migration to Nogales, Sonora, which now sustains a population well in excess of 280,000, many abiding in substandard housing on the city’s periphery and lacking essential services. Though growth has not been as intensive on the US side, Nogales, Arizona sustains a population today of more than 19,000. Nearby Rio Rico, Arizona, a retirement community, logs in at nearly 20,000 to compose a total river adjacent population exceeding 38,000 souls in the combined metropolitan area of Santa Cruz County.

Table 1. Population Growth in Ambos Nogales, 1940–2020.

Year	Nogales, Arizona	Nogales, Sonora	Ambos Nogales (AN)	Decadal Growth, AN
1940	5135	13,866	19,001
1950	6153	24,478	30,631	61%
1960	7286	37,657	44,943	47%
1970	8946	52,108	61,054	36%
1980	15,683	65,587	81,270	33%
1990	19,562	105,873	125,435	54%
2000	20,900	159,787	180,687	44%
2010	20,837	220,292	241,129	33%
2020	19,807	264,782	284,589	18%

Note(s): Sources: Lorey [12]; Nogales, AZ Population History [13], and Nogales Municipality Data [14].

Table 1. Population Growth in Ambos Nogales, 1940–2020.

Year	Nogales, Arizona	Nogales, Sonora	Ambos Nogales (AN)	Decadal Growth, AN
1940	5135	13,866	19,001
1950	6153	24,478	30,631	61%
1960	7286	37,657	44,943	47%
1970	8946	52,108	61,054	36%
1980	15,683	65,587	81,270	33%
1990	19,562	105,873	125,435	54%
2000	20,900	159,787	180,687	44%
2010	20,837	220,292	241,129	33%
2020	19,807	264,782	284,589	18%

Note(s): Sources: Lorey [12]; Nogales, AZ Population History [13], and Nogales Municipality Data [14].

The remarkable demographic surge in the Ambos Nogales metropolitan zone since 1960, particularly the growth of Nogales, Sonora (Table 1), drew heavily on the SCR’s water resources and challenged the capacity of both countries to cope with its consequences. As early as the 1950s, the problem of renegade sewage draining to the U.S. side through Nogales Wash, threatening both surface and groundwater in the riparian system, prompted construction of a binational sewage treatment plant, the NIWTP, completed in 1951. Roughly 70 percent of the influent to the NIWTP originates in Nogales, Sonora [15]. Rising groundwater use on both sides the boundary, depletion of surface flows, and sewage contamination caused the Arizona Interstate Stream Commission to examine the situation in the 1960s, though little was undertaken to engage binationally on water allocation or groundwater management beyond building additional improvements to the NIWTP [16]). Industrial sites on both sides of the boundary bled contaminants to local soils, further threatening the integrity of groundwater supplies [15]. These problems were of sufficient gravity to generate additional IBWC agreements aimed at managing international sewage flows at Ambos Nogales [17,18].

Other water-related problems were evident and worsened as Ambos Nogales grew after 1965. Urbanization in the steep canyon-sides above Nogales Wash exacerbated the problem of flooding during summer-seasonal monsoons, overwhelming inadequate collector systems on the Mexican side and clogging drains with sediments. The persistent threat of flooding through Nogales’ narrow canyons feeding Nogales Wash worsened in the 2000s owing to the inadequacy of storm water mitigation and, as a build-out of border barriers separating the co-adjacent cities, impeded drainage, generating hazards on both sides. The NIWTP’s favorable downstream ecological impact as discharges to the river rose generated worries that riparian renewal would falter should Mexico reclaim the water [19,20], leading ecologists and riparian advocates to propose a Santa Cruz Water and Importation Authority in 2004 [21,22]. The proposed authority never materialized; however, the compounding of these various problems and threats to the riparian system suggests the need for a more comprehensive binational approach to managing transboundary water resources related to the SCR.

5. Managing the Santa Cruz River

The governance setting affecting utilization and management of the SCR watershed in the border region, as with other transboundary rivers and streams, is complex. It exists as an amalgamation of international, national, and subnational political and administrative units whose authority and responsibility for water management and intergovernmental articulation vary by degree regarding specific problems [20]. At the international level, the diplomatic and administrative authority for addressing transboundary issues arising from the SCR rests with the IBWC. The U.S. Section of the IBWC maintains its Southeast Arizona Citizens Forum, which functions as an outreach mechanism and sounding board for the USIBWC’s activities and initiatives [23]. Other binational agencies and programs potentially come to bear on efforts to improve conditions affecting the riparian zone, including the North American Development Bank (NADB), the Commission for Environmental Cooperation (CEC), and cooperative environmental programs conducted under the authority of the 1983 La Paz Agreement on bilateral environmental cooperation (NADB has assisted with financing sanitation and wastewater infrastructure in the border area; CEC provides a mechanism for spotlighting ecological problems in the border region; and the Border XXV Program supports the formation of local binational task forces to address pressing environmental problems along the international boundary). The state-to-state Arizona–Mexico (formerly the Arizona–Sonora) Commission provides a binational forum for developing cooperative initiatives between the two states [24].

On the U.S. side of the boundary where water management is largely in the hands of the U.S. states, responsibility for the sustainable management of the SCR falls to various state agencies, most notably the Arizona Department of Water Resources (ADWR) which implements state water law, and the Santa Cruz Active Management Area that regulates groundwater extraction in the Ambos Nogales and SCR riparian zone [25]. Other Arizona agencies, its Department of Environmental Quality (ADEQ) and Game and Fish Department (ADGF), are guardians of water quality and wildlife resources within and beyond the watershed. Because Arizona rivers are excluded from federal arrangements for the Colorado River, the role of the U.S. federal government is modest and mainly related to environmental enforcement and international treaty implementation [26].

Water governance in Mexico is centralized and dominated by the federal government under constitutional provisions and Mexico’s National Water Law. Article 27 of the Mexican constitution designates all sub-surface natural resources as federal property [27]. Rivers and streams fall under national jurisdiction. The National Water Commission (CONAGUA) administers national water law directly or through concessions permitted by law. Mexican water law provides for the establishment of river basin advisory councils (Consejos de Cuenca) [28], though none have been established for the SCR in its Mexican reach. Some decentralization of Mexican water administration is seen in the management of urban water and sewage systems which in Sonora falls under the administration of the Comisión Estatal de Agua (CEAS). Since 2005, responsibility for urban water and sanitation services officially devolved to the Nogales, Sonora municipality (municipio) and is lodged in its Organismo Operador Municipal de Agua Potable y Saneamiento (OOMAPAS). Despite this decentralization, OOMAPAS still depends on CONAGUA and CEAS for federal financing and some administrative and technical expertise [29]. As other scholars have shown, fiscal capacity can be a significant limitation on a local government’s willingness to enter into transboundary agreements [30].

Over the years, several non-governmental advocacy groups and scholarly institutions have become engaged in various aspects of SCR watershed management (See

Table 2. Santa Cruz River Advocacy Groups.

Water/Environment NGOs	Institutional Groups
Friends of the Santa Cruz	U. Arizona Udall Center
Tucson Water Management Group	COLEF Nogales
Tucson Audubon Society	U. Arizona Water Resources Research Institute
Patagonia Area Resource Alliance	ASU Transborder Studies Department
Santa Fe Ranch Foundation
Sonoran Institute

for list of groups engaged in research and advocacy in the SCR). The most continuously visible and active group for the international stretch of the river, Friends of the Santa Cruz River (FOSCR), was formed in 1991 “to ensure a continued flow of the river’s surface waters, promote the highest river water quality achievable, and to protect and restore the riparian ecosystem and diversity of life supported by the river’s waters” [31]. FOSCR sustains a range of riparian management activities on the U.S. side of the border and was successful in establishing the Santa Cruz River Active Management zone for groundwater monitoring and regulation in the 1990s. In collaboration with other civic groups, it successfully deployed a vegetation inventory and mapping project for the riparian stretch of the SCR water by the NIWTP. In 2017, the FOSCR succeeded in persuading Arizona’s senators to push for federalization of the International Outfall Interceptor pipe channeling Nogales, Sonora sewage to the NIWTP, an aging infrastructure owned by the City of Nogales whose occasional rupture is a source of sewage spillage and contamination in the riparian corridor [32]. The U.S. Congress recently moved to approve that initiative [33]. The FOSCR partners with several environmental advocacy groups but does not maintain partnership relationships with Mexican groups in Nogales, Sonora.

Other advocacy groups include the Sonoran Institute, the Tucson-based Watershed Management Group, Tucson Audubon Society, Patagonia Area Resource Alliance, and the Santa Fe Ranch Foundation. Of these, the Sonoran Institute and the Watershed Management Group deserve special mention. The Sonoran Institute (SI) has been the most active, with an interest that also dates to 1991 and the formation of the FOSCR. While supporting most of the FOSCR’s initiatives, the well-respected and better-resourced Sonoran Institute (SI) took the lead in 2008 in developing a Living River Project designed to generate a range of research and conservation priorities for the SCR watershed [34]. During its annual Santa Cruz River Research Days in 2018, the SI surveyed over 140 university and government researchers on health-of-the-river issues. SI works with civic groups in Ambos Nogales (both cities) to raise awareness of riparian values and needs. It advocates the need for a binational solution to assure the sustainable maintenance of the SCR riparian ecosystem.

The Tucson based Water Management Group (WMG), a non-profit focused on restoring the region’s watershed heritage, is also an important partner for FOSCR, though WMG’s focus centers on health-of-river issues in the northern reach of the SCR watershed [35]. WMG’s Santa Cruz Watershed Collaborative formed in 2018 with a strong policy focus on convening and enabling “watershed leaders to make well-informed management and policy decisions with over two dozen government agencies, non-profits, institutions involved” [36]. Thus far, it has focused on inter-government water policy on the U.S./Arizona side of the boundary but can be relied upon to lend support to the FOSCR and SI transboundary initiatives.

Efforts to restore and seek sustainable binational solutions for the SCR have been supported and bolstered by research institutes and scholars at Arizona and Sonora’s research universities for nearly 40 years; these efforts gained traction with the creation of the Udall Center for Studies in Public Policy (UCSPP) in 1987. Under the leadership of its first director, political scientist Helen Ingram, UCSPP undertook an analysis of binational governance at Ambos Nogales in the earlier 1990s and has since sustained an interest in binational management of the watershed [37]. The University of Arizona’s federally supported Water Resources Research Center has taken a growing interest in the SCR and San Pedro River watersheds and in 2008 joined with sister institutes in New Mexico and Texas as contracting investigators assisting the IBWC in implementing the 2006 Transboundary Aquifer Assessment Act’s Santa Cruz River and San Pedro River aquifer studies, of which the SCR component is still ongoing [38]. Both UCSPP and the WRRC have produced dozens of reports and published papers analyzing various aspects of water management in the SCR and Ambos Nogales.

Sonoran research institutions have close ties with researchers at Arizona’s public research universities and pay some attention to the SCR, though these institutions, most based in Hermosillo, nearly 140 miles south of the boundary, have focused more on municipal water supply, sanitation, and public health in Nogales, Sonora than on ecosystem issues. An exception here is the close collaboration of Mexican investigators with U.S. counterparts in working with the IBWC and CONAGUA on the Sonoran part of the TAAA study of the SCR.

An inventory of stakeholder and advocacy groups for sustainable management of the SCR suggests that there is growing sentiment for strengthening binational management of this important riparian resource, particularly in the area of shared risk mitigation like flood prevention and managing contaminants [39,40], though support for water sharing and apportionment is currently centered on the Arizona side of the boundary. As yet, however, a critical mass does not exist for elevating this issue on the IBWC’s diplomatic agenda. To better understand why, it is useful to look at a similar and more successful instance of binational cooperation, the IBWC’s Minute 320 on the Tijuana River, that may shed light on what is missing in binational advocacy and support for strengthened binational management of the SCR.

6. Ingredients for Success: The Tijuana River as Template

Some 300 miles to the west of the SCR and draining to the Pacific Ocean is the Tijuana River. One of the named treaty rivers in the 1944 Water Treaty, the Tijuana River, like the Santa Cruz, has headwaters north of the boundary and loops into Mexico crossing or touching the boundary three times on its way to the coast [41]. Like the SCR, the Tijuana River was never apportioned, though Article 16 of the 1944 treaty provides a framework for binational cooperation in managing the watercourse [42]. Unlike the SCR, the Tijuana River navigates the largest binational metropolitan zone on the border, crossing the border a final time just four miles east of the coastline where it passes through and sustains the Tijuana River National Estuarine Research Reserve (TRNERR) before draining to the Pacific Ocean [43].

The Tijuana River has for years been both a blessing and a bane for the coadjacent sister cities, a blessing as a water source and a bane as a de facto sewer where it passes through and lies beneath dense Tijuana colonias near its final boundary crossing. The notorious Tijuana sewage problem presents as one of the earliest challenges to the IBWC under its Article 3 sanitation mandate [44]. Spillage to the river contaminated farms, beaches, and coastal waters downstream [45]. Initially, Tijuana’s sewage spillage was managed by building an international connection to San Diego to handle exceedances in Tijuana’s unreliable collector system. The development and build-out of Tijuana led the two countries to construct the South Bay International Water Treatment Plant (SBIWTP) in the 1990s to better manage the problem [46].

Sewage control was not the only problem plaguing the Tijuana River. The potential for groundwater contamination in the downstream riparian zone was noted as early as the 1970s [47]. Periodic floods washed sediments, garbage, and other debris into the estuary, threatening conservation efforts in the TRNERR [48].

While the Tijuana River’s problems were well recognized as early as the 1970s, they resisted a solution, complicated by binational differences in government capacities and priorities. Agreements through the IBWC were reached on flood control and sanitation, but the sanitation facilities’ improvements were chronically eclipsed by the pace of urban growth south of the boundary [46,49]. It was not until the 1990s that stakeholder momentum for better management of the various problems affecting the international reach of the river gathered force.

Several factors appear to account for the successful mobilization of binational support for an IBWC agreement (Minute) facilitating better management of the river. First, advocates for improvements focused entirely on addressing sanitation and environmental hazards related to the river [41]. As with the SCR, Mexico’s ownership of treated wastewater was a potential problem, but was largely ignored by advocacy groups in both countries.

Second, local universities and research institutes played an important role as early as the mid-1990s in spearheading research and convening binational meetings aimed at identifying threats to the river and raising public awareness of its value and the need for binational stewardship of this riparian resource. University researchers took an early lead in convening binational stakeholders interested in the Tijuana River and leveraging state government resources to elevate the issue on the public agenda. A good example of this is the Institute for Regional Studies of the Californias (IRSC) at San Diego State University which took advantage of California’s Proposition 13 (authorizing the formation of watershed boards through the state) to establish a binational watershed advisory board for the Tijuana River [41]. That board, in 2005, produced a binational vision statement for the Tijuana River watershed management that had broad support among researchers, NGOs, and a few governmental stakeholders on the U.S. side of the boundary [41]. Universities were also instrumental in building on this exercise to create a Tijuana River Watershed Task Force under the authority of the binational Border 2012 Program [50]. The Border 2012 Task Force, in turn, helped facilitate the creation of another binational stakeholder group in 2008 joined by a wide range of local governmental entities, the Tijuana River Valley Recovery Team (TRVRT) [51,52]. This body, composed of a range of governments, including representatives from Mexico’s National Water Commission (CONAGUA) and the Tijuana municipality, as well as NGOs, academic institutions, and private sector entities, enlarged and enhanced the strength of the policy advocacy community focused on Tijuana River watershed management. The breadth of this effort, including important governmental entities, academic researchers, and NGOs, is key to the success of the TRVRT that we discuss below.

Formation of TRVRT points to a third factor enabling binational agreement, the presence and persistence of binational policy entrepreneurs invested in promoting watershed awareness and binational cooperation in the Tijuana River Watershed. From the mid-1990s forward, three individuals played an oversized role in advancing binational cooperation on the river. Anchoring advocacy on the Mexican side of the border was Carlos de la Parra, research scholar at El Colegio de la Frontera Norte in Tijuana and past head of Mexico’s federal environmental agency in Baja California. Two U.S. advocates, Paul Ganster, IRSC director, and Oscar Romo, head of the TRNERR, played vital roles in spearheading and coordinating binational efforts to mobilize support for Tijuana River watershed protections. Romo, in particular, after taking the helm at TRNERR in 2005, proved a tireless advocate for improvements and a capable binational public diplomat who worked well with both U.S. and Mexican authorities in building support for strengthened riparian management [53].

A fourth factor contributing to success was timely developments at the IBWC. Two factors were particularly helpful. Beginning in 1999, the USIBWC’s development of its citizens’ forums program began in San Diego and contributed to better community outreach between the USIBWC and San Diego stakeholders concerned with the Tijuana River. [54]. The IBWC’s experience negotiating solutions to water scarcity and ecological restoration challenges on the lower Colorado River after 2000 also produced organizational innovations in the form of binational technical task forces and workgroups tasked with science-driven technical and policy analyses to better inform and guide the Commission’s diplomacy [55]. The inclusion of ecological matters as legitimate objects of the agency’s concern broke new ground, as has been documented by research exploring how environmental concerns have been examined within the U.S.–Mexico water resource governance structure that the 1944 U.S.–Mexico Water Treaty supports [56]. The achievement of a landmark agreement on the Colorado River in 2012, not coincidentally, marked the Commission’s informal embrace of a transboundary watershed perspective that broadened the range of elements that might be discussed on the IBWC’s agenda [57].

These four variables, a focus on hazards and threats other than water availability, the leadership role of university-related research institutes and scholars in focusing attention and convening stakeholders to consider better management approaches and needed improvements for sustainable maintenance of the watershed, the presence of dedicated policy entrepreneurs, and institutional advances at the IBWC, stand out as important influences that proved to be conducive to the IBWC’s decision as early as 2012 to consider working towards a binational agreement that would have strong local support on both sides of the boundary [53]. The result was a framework, Minute 320, establishing work groups tasked with reaching specific substantive agreements (IBWC Minutes) on particular aspects of the hazards problems, including sanitation, confronting the lower reach of the Tijuana River Watershed [4].

There are, of course, other contextual factors that bear upon the achievement of Minute 320. One is certainly the scale and configuration of the contiguous metropolitan zones of Tijuana and San Diego, to include their population sizes, urban build-out, and the persistent adverse impacts of sanitation failures on a broad range of stakeholders in the U.S. reach of the Tijuana River. On the U.S. side of the boundary, multiples of local governments and state agencies, as evident in the TRVRT initiative, were stakeholders in the effort, benefiting indirectly from working within cross-border networks coordinated through the San Diego Association of Governments (SANDAG), a longstanding policy coordination function of San Diego County, the only home-rule county on the U.S.–Mexico border [58].

Even so, the Tijuana River case study spotlights certain factors that may be conducive to binational cooperation on transboundary watershed management as well as certain approaches the IBWC has found useful in advancing binational cooperation on the SCR. A comparison of the advocacy and policy conditions in the two transboundary watersheds sheds light on what might be undertaken to reach an IBWC agreement (Minute) advancing binational cooperation on managing the Santa Cruz River watershed.

7. Santa Cruz River and Tijuana River Advocacy Situation Compared

If we compare the SCR situation to what we see in the recent case of advocacy leading to the IBWC’s adoption of Minute 320 on the Tijuana River, we find some interesting similarities and differences. In some respects, as seen above, these cases look quite similar (see

Table 3. Tijuana River and SCR Advocacy Compared.

Advocacy Variable	Tijuana River Case	Santa Cruz River Case
A. Issue Characteristics
Water Availability an Issue	No	Yes
Water Hazards an Issue	Yes	Yes
B. Advocacy Characteristics
Sustained, university-led research and advocacy	Yes	Some, but less sustained and less general in scope
Presence of Dedicated Policy Entrepreneurs advancing binational solutions	Yes	No
C. Policy Context Characteristics
New IBWC Management Approaches are Available	Yes	Yes
Coordinated Binational Policy Development	Yes	No

). Both involve transboundary rivers heavily impacted by rapid urbanization along the boundary. Both involve binational sanitation problems and international sewage treatment plants discharging treated wastewater to the river. Both involve a concern with riparian hazards including contamination and stormwater management, although in the Tijuana River case, the problems of sedimentation and refuse/garbage accumulation are attendant concerns. Both cases benefit or potentially benefit from advances in IBWC diplomacy and approaches to transboundary watershed management problems in recent years.

However, we also see important differences when we compare these two cases. The fact that water allocation looms much larger in the SCR case suggests a greater potential for binational contention related to water utilization than seen on the Tijuana River in the runup to Minute 320.

The advocacy situation is also different. Though regional research universities have been interested in the SCR for some time, generating many useful studies on particular aspects of SCR riparian ecology, surface flows, groundwater conditions, and water quality hazards, there has been no concerted binational effort to generate a common binational vision for SCR management as seen in the Tijuana River advocacy record. The Sonoran Institute’s ongoing Living River research initiative does engage university and government researchers in understanding the river’s ecological conditions and values but has not yet seen the sustained involvement of leading scholars at Sonoran research universities, diminishing the level of binational stakeholdership in riparian advocacy. Nor has it advanced a concerted sustained effort to realize a binational agreement apart from backing a legislative proposal that the USIBWC assumes ownership of the troubled International Outfall Interceptor pipe delivering Nogales, Sonora’s sewage to the NIWTP (This initiative, backed by Arizona Representative Raul Grijalva, recently gained the approval of the U.S. Congress [33]. Also absent in the SCR case is the clear influence of a particular policy entrepreneur, or entrepreneurs, who may act as advocates and convenors of binational advocacy and research efforts over a sustained period of time.

The policy context also varies. Whereas Tijuana River advocacy benefitted from an established mechanism for informing and mobilizing regional governments on matters of binational policy concern as seen with SANDAG, no such entity exists in southern Arizona. While local county and municipal governments communicate and support SCR conservation, the effort is less well coordinated and sustained in the absence of a body focused on coordinated responses to binational challenges and opportunities. Less forceful Arizona state government commitment to watershed management also contrasts with the vigorous California commitment to building watershed management capacity—supported by Proposition 13’s Watershed Management Program—that helped fund advocacy efforts focused on the Tijuana River [41]. An area of commonality is seen at the binational level where the IBWC’s recent transboundary watershed orientation and related diplomatic innovations for reaching agreements on transboundary water controversies benefits efforts to advance binational cooperation on both rivers [59].

8. Discussion: Advancing Binational Cooperation on the Santa Cruz River

That more needs to be undertaken in strengthening binational management on the SCR seems now to be an article of faith among southern Arizona local governments, university researchers, and environmental groups north of the boundary. Just how this is to be undertaken remains in question. Some insights and suggestions, however, may be gleaned from our comparison of the two riparian cases.

It is apparent that the SCR water allocation issue associated with the NIWTP’s treated effluent remains a disincentive to binational cooperation absent approaches that induce Mexico to allow some effluent to be retained by the United States. Mexico, as seen above, retains full rights to the treated effluent. Nogales, Sonora has already constructed a new wastewater treatment plant south of the city that recaptures some effluent that might otherwise flow downstream to the IOI and the NIWTP [60].

To address this challenge, it seems reasonable that defenders of the SCR consider some form of contractual reimbursement for sustained use of Mexico’s effluent. Several possible avenues present themselves for this purpose. A water trust might be established to acquire long-term lease rights to the NIWTP effluent subject to the constraints of Mexican water law. Another option, drawing from the IBWC’s experience with water conservation on the Rio Grande [61], would be U.S.-funded investments in riparian water conservation on both sides of the boundary with savings in Mexico traded for NIWTP effluent to be dedicated to riparian ecological maintenance. Building Mexican stakeholdership in riparian ecology would also seem a necessary precondition to any water sharing arrangement. This might include some combination of facilitating ecological learning opportunities for Nogales, Sonora schools though field trips to the restored riparian area north of the boundary, investing in SCR ecological restoration south of the boundary, or assistance with financing urban watershed improvements tied to flood control, erosion prevention and remediation, and sanitation improvements channeled through the North American Development Bank and IBWC. Several of these strategies have been entertained by some Arizona advocacy groups but have yet to gain traction in either country.

It is also apparent that focusing on mitigating hazards, particular sewage-related and industrial contamination of surface flows and groundwater, while emphasizing the ecological value of the SCR riparian corridor to both countries, creates incentives for further cooperation [39]. Hazards mitigation is a common, shared interest of both countries and a potential avenue for advancing binational cooperation that may be separated from the more controversial water allocation issue. As the Tijuana River case illustrates, a focus on hazards mitigation draws attention to watershed integrity and sustainability, including a focus on the ecological assets found in the riparian zone. Addressing hazards is a complex challenge, requiring particular solutions tailored to specific hazards. Hazards express differently on each side of the border, but problems like flood control, sanitation, and groundwater contamination have been a source of common concern for decades and require binational solutions to manage as the history of joint efforts to address the threat of sanitation shows. Generating binational momentum for further cooperation safeguarding the SCR is most likely to proceed from this basis.

Addressing the advocacy deficit has no ready solution but would seem to require a more sustained effort by university institutions and researchers in organizing binational advocacy efforts, coordinating with NGOs, and focused on gaining stakeholdership and support from local and state governments in Arizona and Sonora, as well as federal water management institutions like CONAGUA in Mexico. The fact that local governments in southern Arizona lack a built-in coordinating mechanism for binational initiatives like San Diego’s SANDAG means the bar for binational coordination is higher in southern Arizona. Such an effort could take advantage of the IBWC’s citizens forums for the Ambos Nogales region in building a cross-boundary coalition to advance innovative and sustainable solutions to SCR’s compound problems. One constructive initiative that has advanced binational academic partnership is the TAAP’s scholarly study of the SCR aquifer [62] (Mexico’s CILA established its Nogales, Sonora Foro Ciudadano in 2015) [63]. The USIBWC’s Southeast Arizona Citizens’ Forum dates to 2005 [23]. Other issue-specific binational partnerships exist that might be drawn into a coalition advancing binational SCR solutions (for example, the Ambos Nogales Reforestation Partnership [64,65] and the Arizona Border Communities Health Network [66].

The political context for watershed management solutions is certainly weaker in southern Arizona than it is in San Diego County. That reality is not likely to change in the near term. But other contextual factors are more favorable to strengthening binational governance for the SCR. The IBWC’s adoption of technical and policy advisory task forces to address transboundary watershed problems is a useful advance that could be applied to the SCR. The Commission’s recent resort to agreements like Minute 320 suggests that such an approach could also be taken to address the multiple binational problems associated with the SCR watershed.

9. Conclusions

Advancing binational governance of the SCR is certainly challenging and by comparison to the Tijuana River situation, confronts issues, advocacy deficits, and local governance deficits that presently impede further cooperation. Yet, some aspects of the binational and political context are favorable. Many of the advocacy building blocks are already in place, including past sanitation agreements, binational cooperation on groundwater studies, and multiple advocacy groups interested in sustaining the riparian resources of the river, north and south of the boundary. The IBWC’s embrace of technical and policy advisory teams and binational policy framework agreements allows the two countries to set a flexible agenda for the crafting of specific subsidiary agreements that strengthen binational cooperation on particular transboundary watersheds, avoiding all-or-nothing approaches that impede incremental progress on watershed management. These pragmatic devices are conducive to further binational advances addressing aspects of SCR management in the years ahead. These ideas are also consistent with insights gained in our review of the relevant literature on transboundary watershed management and could support discussions towards the development of the IBWC Minutes on in the Santa Cruz River Watershed.