- This report examines current efforts by the U.S. and Mexico to establish binational projects for developing new water sources in the lower Colorado River basin (LCBR) border region.
- Declared water shortage cuts to LCBR states and Mexico reduced Mexico’s annual Colorado River water allotment by 104,000 acre-feet and the allotment for U.S. states (Arizona, California, and Nevada) by 617,000 acre-feet in 2022-2023, triggering a search for new water sources (water augmentation) throughout the region.
- Wastewater recycling, seawater desalination, and new groundwater extraction top the list of potential new water sources other than conservation in the LCRB border area.
- Water recycling is a promising new water source now being pursued at Tijuana and San Diego, Mexicali and Calexico, San Luis Rio Colorado, and Yuma. Projects at Tijuana-San Diego and Mexicali have binational components and illustrate the potential for further binational cooperation on wastewater recycling as a new water source. But wastewater recycling falls well short of making up Colorado River shortage deficits affecting the LCRB region.
- Seawater desalination technology has the greatest binational project potential for delivering large volumes of water that offset existing or anticipated Colorado River water shortages, albeit at very high financial cost. Current estimates for desalination plants on the Sea of Cortez range from $3-$5.5 billion. Mexico’s support for proposed projects is not assured, however, as evident in variable responses to IDE Technologies’ proposal to develop and pipe desalinated water to the Phoenix area and a recently revived project at Playas de Rosarito near Tijuana. Environmental considerations may also complicate the development of recently proposed projects.
- New groundwater development is less promising. The Mexican side of the LCRB border region relies heavily on groundwater for agricultural and municipal-industrial uses. These sources are already overexploited, and access to these waters remains a source of contention among stakeholders. Brackish groundwater, however, is recoverable through desalination and exists in abundance in the Yuma and Imperial Valleys. It remains a potential new water source, although its connection to Colorado River irrigation seepage will likely complicate future binational utilization.
- Current prospects for binational new water projects are limited with the exception of highly expensive and ecologically damaging seawater desalination facilities. Efforts at water conservation — including developing greater efficiencies in beneficial use and curtailing demand — remain the most promising avenues for coping with water scarcity in the LCRB border region.
Though still awaiting formal federal approval, the much-heralded lower Colorado River basin concession in May 2023 by Arizona, California, and Nevada — consenting to an unprecedented curtailment of the use of 3 million acre-feet of Colorado River water through 2026 — spotlights the severity of the basin-wide drought now afflicting the lower-Colorado River region, including Mexico (Flavelle 2023). Since 2022, mandated curtailments to LCRB states and Mexico in response to declining Lake Mead reservoir storage levels have, under the terms of IBWC Minute 323 (2017), left Mexico with a Colorado River water allotment deficit of 104,000 acre-feet (af) and the U.S. LCRB states with a deficit of 617,000 af (USBR 2022; Knutson 2022).
For over a decade, dating to Minute 319 of the International Boundary and Water Commission (IBWC) in 2012, the persistent scarcity in Colorado River surface flows has driven both countries to explore new water sources as essential buffers to their water security. While many of these water augmentation initiatives have proceeded absent a binational cooperative component, both IBWC binational shortage-sharing minutes, Minute 319 and Minute 323, envisioned cooperative binational efforts to conserve and develop new water sources. Minute 323 specifically references wastewater effluent reclamation and desalination as potential new water sources that might lend themselves to joint development (IBWC 2012; 2017, 20). Other water professionals point to groundwater as a potential new water source to be developed (O’Neill and Boyer 2023, 497).
This report reviews the range of potential new water sources available in the LCRB border region for compensating drought-induced water deficits and considers existing initiatives to put these resources to use. It concludes by reflecting on the prospects for binational cooperation in sustainably developing these resources to maintain water security in the LCRB region.
Figure 1 — Colorado River Basin
Water Recycling Initiatives
Water recycling refers to the reclaiming of water that is treated and reused for beneficial purposes, including agriculture, irrigation, potable drinking water, groundwater recharge, industrial processes, and environmental restoration (U.S. EPA 2022a). Reclaiming and reusing existing water sources is by far the most accessible and least costly of the new water sources now being pursued in the border region. The prospects for supplementing Colorado River-sourced water with reclaimed water is suggested by a number of currently implemented or planned projects on the dockets of boundary adjacent communities in the lower Colorado River region. These include extant and proposed works at Tijuana and San Diego, Mexicali-Calexico-New River, and San Luis Rio Colorado.
Tijuana-San Diego. Chronic sewage and floodwater spillage to the Tijuana River has vexed adjoining communities at Tijuana and San Diego dating as far back as the 1940s. These problems are the reason for the establishment and expansion of the South Bay International Wastewater Treatment Plant (SBIWTP) since 1996 (Mumme 2023). Tijuana River cleanup and management have also driven repeated proposals for effluent reclamation and reuse. An ill-fated private sector initiative that, if implemented, would have recaptured a projected 50 million gallons a day (mgd) for treatment and potential reuse in Mexico was rejected in 2008 (Davis 2008), but the prospect for an eventual sewage reclamation project never quite died. Reclamation of Tijuana River effluent was identified as a water augmentation option in Minute 323 and recently took flight with the massive proposed expansion of the SBIWTP and related improvements to wastewater capture and treatment in Tijuana. This project, authorized as part of U.S. congressional approval of the United States-Mexico-Canada Agreement (USMCA) in 2019, was binationally approved in the IBWC’s Minute 328, signed July 19, 2022 (IBWC 2022). A joint U.S. Environmental Protection Agency (U.S. EPA) and USIBWC Final Programmatic Environmental Statement (FPEIS) was published in November 2022 (U.S. EPA 2022b).
Both Minute 328 and the FPEIS commit to effluent reuse of treated Tijuana River water for Tijuana. Of the suite of U.S. and Mexican linked projects aimed at Tijuana River pollution mitigation, Project H commits to works transferring treated effluent from two Tijuana wastewater treatment plants to storage in Rodriguez Reservoir that would otherwise drain to the Tijuana River. Project I authorizes new works conveying up to 40 mgd (122.8 af daily) of treated effluent from the SBIWTP to Tijuana for beneficial use (U.S. EPA and USIBWC 2023).
North of the border, other water reclamation works are underway as part of San Diego’s Pure Water San Diego (PWSD) program begun in 2016. A vital part of this initiative reclaims effluent treated to tertiary water treatment standards at San Diego’s South Bay Wastewater Treatment Plant (SBWTP), which is adjacent to the SBIWTP near the Tijuana River bed just north of the international boundary, for discharge to the Otay Reservoir southeast of San Diego. Taken with other components, the PWSD projects would salvage up to 83 mgd (254.7 af daily), nearly half of the city’s projected water needs by 2035 (Garrick 2021).
Though technically separate, both the SBIWTP and PWSD projects represent unprecedented regional and binational efforts to build water security and hedge against reliance on Colorado River water resources going forward. Both projects are key elements in reducing historic contamination and waste deposition to the Tijuana River estuary with benefits to beach waters in both countries at and near the international boundary.
Mexicali-Calexico. Wastewater reclamation is also a component of a longstanding effort to mitigate chronic contamination of the notorious New River that crosses the border at Mexicali and Calexico. The New River, which originates just south of Mexicali and drains to the Salton Sea roughly 60 miles north of the international line, is fed by agriculture runoff on both sides of the boundary and treated and untreated sewage from Mexicali (Del Real 2019). Binational remediation based on new construction and renovation of Mexicali’s sanitation infrastructure and treatment of Mexicali wastewater — works completed in 2007 under IBWC supervision with financing from the U.S. EPA and North American Development Bank — enabled the transfer of treated effluent to support ecological restoration projects along the Colorado River in Mexico in fulfillment of commitments made in Minute 319, endorsed and sustained by Minute 323 (IBWC 2012; 2017; California Water Boards 2020). A further New River improvement project, authorized and funded in 2023, diverts treated Calexico wastewater to the New River just north of the international boundary to improve its water quality as it flows to its Salton Sea terminus (CALEPA 2023; Calexico Chronicle 2023).
These limited reclamation efforts related to transboundary New River sewage flows spotlight the underdevelopment and growing opportunities for wastewater reclamation in the Mexicali-Calexico region. A recent study of the Mexicali Valley’s water needs finds that the Mexicali region is running a deficit of 449 million cubic meters (364,010 af) annually, equivalent to 24% of its annual treaty allotment from the Colorado River (Rubio-Velazquez 2020, 109-111; Hernandez-Cruz et al. 2023). It may well need as much as 2 million af — 30% more water than the 1.5 million af it is allotted by treaty from the Colorado River — by the end of this decade (2030) to sustain its present level of water security. Mexico’s National Water Commission and the IBWC are keenly focused on achieving greater irrigation water efficiencies to bolster the region’s available water. But there is little doubt that water reclamation will need to play a larger role in Mexicali’s water future going forward.
San Luis Rio Colorado-Yuma. Among the most innovative water reclamation projects found in the LCRB region is that in the city of San Luis Rio Colorado (SLRC) in Sonora, just 25 miles south of Yuma, Arizona. SLRC relies exclusively on groundwater mined from the San Luis Mesa east of the Colorado River for its municipal water supply. There, a wastewater treatment plant originally constructed in 2006 has been harnessed to constructed filtration ponds to achieve a tertiary level of water treatment. Water from this wetland, the Humedal Cucapá, is used to replenish SLRC’s aquifer and develop an extensive (20 hectare) forest of trees and shrubs, or bosque, that since 2018 performs valuable ecosystem services for the Colorado River region just south of the international line (Garcia Garza 2018; EL Sol 2020). With an effluent output exceeding 8,000 acre-feet of water annually, this project, one of the most advanced ecosystem-supporting wastewater projects in Mexico, now plays a vital role in efforts to restore ecological vitality to the riparian corridor below the boundary. Pronatura Noroeste, with the backing of local officials and student volunteers, is now reforesting an additional 6 hectares in this ongoing project (Pronatura Noroeste 2023; Garcia Garza 2018).
Across the border, SLRC’s’ sister city of San Luis, Arizona, which relies entirely on groundwater for its municipal needs, is also using its treated wastewater as groundwater recharge. The nearby city of Yuma, Arizona, is currently recycling upward of 16,000 acre-feet annually from its three municipal wastewater treatment plants, producing highly treated water that is used for aquifer recharge or discharged via the Gila River bed to the Colorado River below Imperial Dam. This water supports restored wetland and riparian vegetation along the Colorado Rivers near Yuma (City of Yuma 2016; Briggs and Cornelius 1998).
Of the various new water alternatives outlined in Minute 323, seawater desalination has drawn the most attention, due not least to former Arizona Governor Doug Ducey’s recent initiative to independently engage Israel’s IDE Technologies in approaching Mexico with a proposal to develop the world’s largest desalination project in Puerto Peñasco, 80 miles south of the boundary on the Sea of Cortez (Arizona Governor’s Office 2022; KGUN 2022; Preciado 2023). Seawater desalination proposals in the lower Colorado River region are not new, dating back to the 1960s. Desalination proposals resurfaced with the region-wide drought. The IBWC’s’ Minute 323 specifically mentioned two leading prospects: desalination on the Sea of Cortez and on the Pacific Coast at Playas de Rosarito near Tijuana (IBWC 2017). Both projects have recently gained traction.
The Arizona-pushed project at Puerto Peñasco departs substantially from earlier recommendations of the Minute 323 Binational Desalination Workgroup’s recommendations in 2020 (IBWC 2017; Black and Veatch 2020). The 2020 study identified five potential opportunities for a Sea of Cortez desalination plant and assumed each would produce approximately 100,000 af of water a year with the potential to combine opportunities to deliver up to 200,000 af per year (Black and Veatch 2020). The cost per acre-foot was estimated at $2,000 with annual operating costs falling between $70-$119 million, and total costs ranging between $3-$5 billion (Black and Veatch 2020). Treated water would be delivered via a 196-mile pipeline to Mexico’s Morelos Dam to satisfy U.S. water deliveries to Mexico, allowing states like Arizona to withdraw more of the Colorado River’s flow upstream. The IBWC-commissioned study’s finding that a Sea of Cortez “desal” project was technically and economically feasible sparked several Arizona proposals for pursuing some version of the plan (O’Neill and Boyer 2023, 493). IDE, however, with Ducey’s tacit support, simply side-stepped the binational IBWC process and advanced its own proposal, gaining the exploratory support of Arizona’s Water Infrastructure Finance Authority (WIFA) in December 2022 (Schutsky 2020).
IDE has a successful record of building seawater desalination plants in the Middle East, India, China, and Australia. It also built the largest desalination plant currently operating in the U.S. at Carlsbad, California, in San Diego County (IDE 2023). Its proposed Puerto Peñasco facility is considerably more ambitious than the options proposed in the Black and Veatch 2020 study. As proposed, the $5.5 billion plant would be privately funded with an eventual capacity to produce and deliver 1,000,000 acre-feet of freshwater annually at an estimated end-user acre-foot cost of $2,500 — conveyed 200 miles via pipeline to intersect with the Central Arizona Project canal in Maricopa County (Allhands 2022; Holmes 2022).
Complicating consideration of this proposal is uncertainty as to Mexico’s support. IDE claims to have courted and gained the tentative support of Mexico’s president and Sonora’s governor in advance of its presentation to Arizona’s WIFA. Mexican President Andrés Manuel López Obrador indicated he would likely approve the project in the absence of local opposition. Sonoran governor Alfonso Durazo, however, has given mixed signals concerning his support for the project, initially endorsing the proposal and then indicating he opposed it after encountering political criticism of the project’s potential adverse environmental impacts (Bregel 2023). The extent of Mexican support remains unknown as of July 2023.
Yet another seawater desalination project has been under consideration for over a decade at Playas de Rosarito near Tijuana (Sanchez Munguia 2021). This project, though technically feasible, was nixed in 2020 by Baja California Governor Jaime Bonilla due to financial concerns, including an unfavorable dollar to peso exchange rate, increased construction costs, and the need to spend $7.75 million per month for years to pay for the plant (BNamericas 2022; MND Staff 2020). However, Consolidated Water, an investor in the plant, filed an arbitration claim in February 2022 seeking to recover $51 million in lost investments over the plant’s cancellation, claiming the government illegally breached the contract (BNamericas 2022). As a result, Baja California is considering moving forward with the project because of the financial problems posed by cancelling it (BNamericas 2022). However, it may seek to cover the costs by exporting desalinated water to serve the Otay Water District in San Diego County (Hernandez 2022; Cervantez 2022).
New Groundwater Availability
Of the various available water augmentation options in the lower Colorado River border region, groundwater may be the most attractive short- and long-term water source (Castle et al. 2014). Border communities and irrigators on both sides of the boundary already rank among the most groundwater-reliant water users in North America, a fact that holds from Tijuana to El Paso (Mumme 2022). Management of groundwater varies across the boundary, with U.S. border states regulating extractions in their jurisdictions, and Mexico’s federal government, acting through its federal water commission, CONAGUA, regulating extractions in Baja California, Sonora, and nationwide (Eckstein 2012). Although a number of border communities, including major sister cities, share common aquifers, little binational progress on jointly managing transboundary sources has been realized in the post-WWII period, aside from a narrow agreement to limit withdrawals on the San Luis Mesa near the international boundary in 1973 (Megdal et al. 2022; USBR 2023b).
The prospect of sustainable new groundwater development along the border in the LCRB zone is limited at present. Known freshwater aquifers are already being utilized — in most cases unsustainably on both sides of the boundary with withdrawals exceeding freshwater inputs. Tijuana, which sources 95% of its water via aqueduct from the Colorado River, draws roughly 5% of its water supply from groundwater wells along the Rio Alamar tributary to the Tijuana River and a few other wells below El Carrizo and Rodriguez Dams. These aquifers are already overexploited and of low quality with little potential as new water sources (Gonzales Estevez and Sanchez Munguia 2013).
Further east in the Mexicali Valley, groundwater plays a major role in the region’s water budget. The Colorado River is king in the Mexicali Valley, but groundwater has historically supplemented the region’s water supply dating as far back as the 1950s, with additional wells added during the protracted bilateral dispute over Colorado River salinity in the 1960s.
Today, the Mexicali aquifer, part of the greater lower Colorado River aquifer, supplies 31% of the region’s water supply and is seriously over-drafted (IMTA 2020; Hernandez-Cruz et al. 2023). Activation of Minute 323’s Colorado River drought contingency conservation rules has reduced the region’s surface water supply by 7% (104,000 acre-feet) for 2023 (USBR 2022), putting further pressure on the aquifer. Mexico’s CONAGUA estimates that Baja California’s aquifers are on average 37% overexploited, with the Mexicali aquifer the most overused. CONAGUA projects a 47% deficit there by 2035 (Cortez-Lara 2020, 6).
Agriculture is by far the greatest water consumer in the region accounting for 85% of all water consumption (IMTA 2020). Nearly 29% of total agricultural water use, however, derives from groundwater extraction (Rangel and Dafonte 2018). Urban and industrial water use, centered in Mexicali, takes 14.7% of the Mexicali Valley’s available water, 92% of this from groundwater, with 37% of all concessioned groundwater rights (IMTA 2020). Mexicali’s urban water demand has been increasing by nearly 3% annually through 2035, and much of this is projected to come from transfer of agricultural groundwater rights to urban uses (Cortez-Lara 2020). The potential for serious conflict over groundwater extraction was recently seen in the political backlash to the proposed expansion of the Constellation Brands brewery in Mexicali, a $2 billion project whose projected water needs, at least 70% to be groundwater-sourced, were estimated to double the water consumption of all other industries in the city (Cortez-Lara 2020). The project was eventually nixed by Mexico’s federal government in 2020 but drew attention to growing urban concerns with access to groundwater in Mexicali (Cortez-Lara 2020).
North of the boundary in the Imperial Valley, Colorado River surface water supplies over 98% of all water used in Imperial County and all water used within the boundary of the vast Imperial Irrigations District. Imperial Valley groundwater is highly saline and not regarded as suitable for domestic consumption (IID 2023). Nevertheless, several of the region’s smallest communities rely on groundwater wells, including the unincorporated community of Ocotillo just west of Calexico, which taps freshwater from the Borrego Valley groundwater basin spanning the international boundary (CDWR 2018).
East of the Colorado River, Mexico’s San Luis Valley relies heavily on groundwater, including groundwater north of the boundary. Much of the irrigation water in the San Luis, Sonora region derives from San Luis Mesa pumped groundwater in the Yuma Valley delivered to Mexico at the southern international boundary as part of Mexico’s treaty allotment under the terms of IBWC Minute 242. Mexico’s Irrigation District 14 and the city of San Luis Rio Colorado also rely on groundwater wells near the international boundary, though pumping in the immediate boundary region by either country is limited to 160,000 acre-feet annually under the terms of Minute 242 (USBR 2023b). Yuma area irrigators and the city of Yuma rely exclusively on Colorado River surface water, although a number of smaller communities in Yuma County, including San Luis and Somerton, depend wholly or partly on groundwater. Saline groundwater is pumped from the Gila Irrigation Unit as a protective measure (Yuma County 2023). That water, blended with Colorado River water, is delivered to Mexico in fulfillment of treaty obligations. Long-term irrigation in the Yuma Valley coupled with seepage from the Colorado River is thought to endow the Yuma region with abundant local groundwater resources, though groundwater quality varies throughout the region (Yuma County 2023). It is worth noting that Yuma County is not included as one of Arizona’s five groundwater Active Management Areas (ADWR 2022).
Brackish Water Desalination
Yet another set of potential water augmentation projects targets desalination of brackish water along the boundary. Brackish water subsumes a wide spectrum of non-potable water sources affected by excess salinity, other mineralization, or pollution. Desalination of brackish water, depending on the degree of degradation, may be less costly than seawater desalination, hence its attraction as a potential new water source (NGWA 2023). Over the past decade, two brackish groundwater desalination plants have been constructed along the U.S.-Mexico boundary — one at Brownsville, Texas, the other at El Paso, Texas — both developed for municipal use (Mumme 2021). Arizona’s Water Augmentation Council’s Desalination Committee has also targeted Yuma’s groundwater mound for possible brackish water desalination (see Figure 2).
Only one such facility, the international desalination plant at Yuma, Arizona, is currently found in the immediate boundary area within the LCRB. This 31-year-old facility, an artifact of the salinity dispute on the Colorado River in the 1960s and the first such facility constructed in North America, has rarely operated. Its usefulness for meeting 1944 Treaty obligations as set in Minute 242 has been largely eclipsed by water abundance in the 1990s, high operating costs, and increasingly obsolete technology associated with its design (Hansen 2022). Originally intended to produce up to 78,000 af of freshwater from Wellton Mohawk Irrigation District’s saline groundwater discharge to reduce the salinity of Mexico’s Colorado River treaty water, the brackish water was instead shipped by canal to a terminus at Mexico’s Ciénega de Santa Clara, roughly 60 miles south of the southern international boundary (USBR 2023a). The plant was briefly taken out of mothballs and operated on a pilot basis in 2010 but has since been dormant. However, it’s still valued as a potential freshwater source for U.S. users in the lower Colorado River zone, provided U.S. salinity management obligations on the river are met (Perry 2010). Recent critics have argued the plant should simply be replaced with a new, more efficient facility, but that idea has yet to gain traction with U.S. Colorado River Basin authorities.
The only other recent proposals for brackish water desalination along or near the boundary in the LCRB consider the potential utility of New River flows at Mexicali-Calexico and possible development of the Yuma groundwater mound. Minute 323 mentioned the potential desalination of New River flows reaching the international boundary (IBWC 2017). That project has not been pursued and appears to have been set aside in favor of the New River water improvement project at Calexico described earlier in this report. The Arizona Water Augmentation Council’s Desalination Committee in 2018 also targeted Yuma’s groundwater mound for possible brackish water desalination (see Figure 2).
Figure 2 — Brackish Groundwater Pools in Arizona
What is certain is that pools of brackish groundwater, the residual of over a century of freshwater irrigation in the lower Colorado River region, are available for future exploitation should authorities in both countries decide to develop these resources. At present, there appears to be limited interest in Arizona, California, and Mexico in pursuing this augmentation option in the near term, though rising water insecurity throughout the region may alter this reckoning in the years ahead.
Prospects for Joint Projects
The preceding review of potential new water sources in the LCRB border area suggests that, short of very costly investments in seawater desalination, the capacity to fill current Colorado River water deficits affecting the region from new water sources is quite limited. Wastewater reclamation is a potential new water source and one of the most promising arenas for binational cooperative projects, as seen in existing projects at Tijuana and San Diego and Mexicali. However, the potential volume of recapturable “new” water from wastewater reclamation projects, either national or binational, falls well short of filling current shortages affecting Colorado River water stakeholders in the border region. The reclamation projects currently approved at Tijuana-San Diego, for example, including PWSD’s projected output, at best recapture well under 200,000 af water annually. Elsewhere, at Mexicali, San Luis Rio Colorado, San Luis, and Yuma, reclaimed effluents are already dedicated to ecological restoration or groundwater replenishment and as such are less available for satisfying recent LCRB shortage-triggered surface water deficits — unless, of course, those existing reclaimed water uses are repurposed. All the same, water reclamation projects and uses for salvaged effluent water have been, and are likely to continue to be, a fertile arena for binational cooperation as evident from recent and ongoing effluent reclamation projects.
Opportunity for resorting to groundwater as a new water source is also limited with poor joint project potential at present. Border cities and many irrigated farms, particularly in Mexico, rely heavily on groundwater as reported above. Key aquifers are not being managed sustainably, resulting in aquifer depletion in groundwater-dependent zones. LCRB surface water shortage has already incentivized additional resort to these aquifers to sustain water availability. Binational progress toward jointly managing transboundary aquifers has been painfully slow to emerge (Mumme 2022), limiting the opportunity for binational cooperation on managing shared groundwater stocks like the Colorado River Aquifer in the border area. However, the known abundance of brackish groundwater in the region, particularly north of the boundary, suggests that these resources may eventually be attractive future targets for desalination to supplement deficits and satisfy potable water demand on both sides of the boundary. The fact that much of the water in the Colorado River Aquifer is tied to historic irrigation filtration complicates the binational marketing and utilization of the aquifer’s desalinated brackish groundwater, as the U.S. has historically claimed this water as part of its surface treaty water entitlement.
Although seawater desalination comes at a steep financial and environmental price, it currently harbors the greatest joint project potential and short-term promise other than conservation for filling the water deficit gap in the lower Colorado region. As seen above, the Sea of Cortez source proposals all call for investment of $3-$5.5 billion and millions of dollars in operating costs to deliver between 100,000 and 1,000,000 af of potable water annually. These projects all risk some environmental damage to the rich upper Sea of Cortez aquatic ecosystem and require multiple power stations and up to 200 miles of conveyance infrastructure that must navigate through or around multiple protected areas on both sides of the boundary. While the IBWC-sponsored Black and Veatch exploratory study was conducted on a binational basis, envisioning projects of mutual benefit for Mexico and the United States, the IDE study was undertaken in a less transparent and unilateral fashion that lent the appearance of an Arizona water grab, an image IDE has since labored to dispel with various offers of potential investments in Sonoran communities, including Hermosillo, the state capital, as well as Puerto Peñasco. In short, numerous permitting and political barriers need to be overcome before any of these Sea of Cortez projects go forward. Not the least of these is ensuring a decision-making process that has popular support and the diplomatic endorsement of both federal and state governments and the IBWC. The resuscitated Playas de Rosarito desalination project confronts similar headwinds but has already obtained federal permits for transporting water across the international boundary. It remains politically controversial in Baja California, both for its projected costs and potential ecological damage to the binationally shared aquatic ecosystem at Tijuana and San Diego (Sanchez Mungia 2021).
In sum, the prospects for binational cooperation in developing new water sources in the LCRB border region are decidedly mixed. As Minute 323 suggests, wastewater reclamation and seawater desalination are certainly the leading candidates for filling current LCRB surface water deficits and hedging against drought in the near term (i.e., the next five to 10 years). The limited potential for additional binational reclamation projects in the region coupled with the high financial and environmental costs of desalination underscore the need for greater conservation and better regulation of water uses throughout the Colorado River border region, in Mexico as well as the United States.
 Note: All monetary values in this paper are in U.S. dollars.
 Opportunity 1 — Reverse osmosis desalination facility located between Bahia San Jorge and Puerto Lobos utilizing ocean discharge/dispersion for brine management, with delivery of treated water to the Northerly International Boundary (Morelos Dam) for exchange.
Opportunity 2 — Reverse osmosis desalination facility co-located with a pumped storage hydropower facility south of Puerto Libertad, utilizing ocean discharge/dispersion for brine management, with delivery of treated water to Morelos Dam for exchange.
Opportunity 3 — Reverse osmosis desalination facility located near Playa Encanto utilizing ocean discharge/dispersion for brine management, with delivery of treated water to Morelos Dam for exchange.
Opportunity 4 — Thermal distillation facility co-located at the power plant in Puerto Libertad utilizing ocean discharge/dispersion for brine management, with delivery of treated water to Morelos Dam for exchange.
Opportunity 5 — Reverse osmosis desalination facility co-located at the power plant in Puerto Libertad utilizing ocean discharge/dispersion for brine management, with delivery of treated water to Morelos Dam for exchange.
 Analysis of the Yuma groundwater mound is found in Dickinson et al. 2006.
 The proposed Arizona-IDE project, for example, cuts though the Organ Pipe National Monument, which is sure to generate considerable public controversy.
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