By Vicente Calderón.

Some residents are still waiting for tap water to fully return to their homes after service was interrupted, once again, in the cities of Tijuana and Playas de Rosarito.

More than 200 neighborhoods across both municipalities on Mexico's northern border went without water, or had only irregular supply, earlier this month due to a mechanical failure at the El Carrizo Dam. Its pumping system moves water out of the El Carrizo reservoir, the final storage point along the aqueduct that carries water from the Colorado River — whose source lies in the Rocky Mountains of the United States — toward the El Florido treatment plant that supplies the city's distribution network.

The local water authority, CESPT (Comisión Estatal de Servicios Públicos de Tijuana), said in a press release dated July 8 that the failure caused a 12 percent reduction in water inflow to the city's distribution system.

"Time for you to restore service on Colonia El Pípila, it's urgent! Too many days already!" said Elizabeth Bacio in a comment on CESPT's official Facebook page.

Water did not flow, but anger did — on social media, from residents facing a hot summer with failing service.

"We are still without water on Colonia Mariano Matamoros," Tania Andrade wrote in the comments section of the state agency's official account, after five days without service.

By Tuesday, July 14, CESPT announced that service had begun returning to about 90 percent of the affected areas. Days later, roughly 10 percent of the original area was still without regular service, even as CESPT touted the repair as a success completed in record time. For residents in the hillside neighborhoods, the emergency measures fell short.

"Praderas de la Mesa, in the higher section, not even a drop of water since Tuesday, and the pipas [water delivery trucks] that you say are distributing water for free don't go up to the colonias on top of the hills," said Martha Gonzalez, another resident, in comments to CESPT.

She was referring to the emergency tanker trucks the government dispatched to affected neighborhoods to offset the lack of regular service — an alternative that, for many, wasn't enough. Fiona Villanueva, another concerned resident, said one truck did come by her area, but the water "was only good for the bathroom" since it wasn't clean.

While Baja border residents see their lives severely impacted by another dry spell, the federal government is trying to overcome the obstacles to building a huge desalination plant. The ambitious project has faced trouble and delays for more than a decade.

The most recent setback was a failed bidding process to find the right company to build the main facility, which will use reverse osmosis technology. On June 3, Mexico's water authority, Conagua, declared the second bidding process for the Rosarito desalination plant void; none of the seven consortiums that submitted proposals met all the technical and financial specifications.

On July 7 — the same day the El Carrizo pump failed — the federal agency published an internal memorandum launching a new procurement procedure in which Conagua will directly invite a minimum of three qualified companies, rather than opening the process to any interested bidder as it did in the two prior rounds.

Cox Energy, S.A.B. de C.V., a subsidiary of the Spanish company of the same name, was one of the companies leading a group of participants. Another was Acciona Agua de México, S. de R.L. de C.V., also a Spanish company with a long history in Mexico, bidding as part of a larger group of participants. And the third was Techno Arrendamientos y Construcciones, S.A. de C.V., a Mexican company bidding with the support of other Mexican and foreign enterprises.

According to the published calendar, the process should advance before the end of July, when officials are expected to decide which group wins the invitation.

The plant has become the region's promised solution: a 2,200-liter-per-second facility expected to increase water availability for Tijuana and Playas de Rosarito by 45 percent, according to federal officials. The project carries an estimated cost of roughly 12 billion pesos (around 840 million U.S. dollars), funded through a combination of federal and state resources.

President Claudia Sheinbaum addressed the stalled project directly on June 25, after the second bidding round had already failed. "Yes, we are going to build it. ( ) it's the only way to bring water to Rosarito and Tijuana," she said during her morning press conference. She added that, despite the failed tender, the government would move forward through a new competitive process.

At the Autonomous University of Baja California (UABC), researchers studying the governance challenges around desalination have documented a pattern of fragmented water management that has persisted for decades.

Dr. Mariana Villada Canela, of UABC's Institute of Oceanological Research, leads a study on participatory governance in desalination. Her team reviewed 110 technical and regulatory documents, analyzed international experience from Spain, Israel, and Saudi Arabia, and surveyed communities in Tijuana and San Quintín,(another Baja California municipality to the south). The findings reveal deep concerns about who will benefit from the plant and how decisions are being made.

"The population wants to participate, be heard, and have access to clear information," Villada Canela stated in a July 6 press release from UABC. "Social trust is indispensable for any climate adaptation strategy."

Her research identified a critical gap: there is currently no specific legislation governing desalination in Mexico, no clear criteria for disposing of the salty brine the process produces, and no formal mechanisms for citizen participation in major water projects. According to the study, vulnerable groups — fishermen, indigenous communities, small farmers, and families with limited access to water — stand to be most affected by both the potential benefits and environmental risks of desalination, yet their voices are seldom heard in the planning stages.

The UABC study also documented public opinion: residents recognize the need for new water sources and express hope that desalination could improve access. Yet that hope is tempered by distrust of the government institutions managing water and concerns about rising costs if private companies operate the plant.

The July 7 crisis exposed, once again, the precariousness of Tijuana's water infrastructure. The city depends almost entirely on a single source: the Colorado River aqueduct, with El Carrizo as its last stop before treatment and distribution. When any component of that pipeline or treatment system fails — as happened with El Carrizo — the impact is immediate, and for residents in hillside neighborhoods without reliable access to tanker trucks, it can stretch on for days.

The desalination plant is meant to reduce that vulnerability by adding a second major source. With a new procurement process now underway and a presidential commitment on record, the project appears closer to breaking ground than it has in years. Yet with two failed bids already behind it, Tijuana faces a familiar pattern: infrastructure breaks, emergency crews distribute water by truck, repairs are made, and life slowly returns to normal — until the next failure.

For residents like Martha Gonzalez and Fiona Villanueva, still waiting days after the pumps were supposed to be fixed, the promise of a desalination plant years down the road offers little comfort today.

Whether the plant will be built before the next crisis strikes remains an open question.