Growing Water Smart in US–Mexico Border Communities

The semiarid cities of Nogales, Arizona, and Nogales, Sonora, technically stand on separate sides of the US–Mexico border. But together, they form a transborder metropolis known as Ambos Nogales (Both Nogales). These sister cities share a binational economy and culture, and they also share the same watershed—one where summer monsoons bring half a year’s worth of rain in two months.

On the steep, hilly, and more populous Mexican side, that deluge often turns deadly. In August 2022, three people in Nogales, Sonora, including two young children, were killed as heavy monsoon rains flooded the streets and trapped them inside vehicles. The summer before, flash flooding there claimed the life of a 24-year-old woman who had recently earned her civil engineering degree.

“Stormwater management is one of the major issues for the Ambos Nogales area,” says Joaquin Marruffo, border programs manager at the Arizona Department of Environmental Quality. “Almost every monsoon season, at least one person dies on the Mexican side of the border [due to stormwater flooding], so that should be priority number one for local governments and for us as public officials.”

Like other border towns in Mexico, Nogales has grown rapidly in the last two decades; the population increased 20 percent between 2010 and 2020, as people from other areas moved there seeking work or hoping to enter the US. This growth has largely been unplanned, resulting in settlements springing up “in places that shouldn’t be established,” Marruffo says, “such as the top of the hills or where there is a floodplain.”

The heavy rains also wreak havoc on property and infrastructure, and pollute local waterways on both sides of the border with industrial contaminants, sediment, and sewage overflow. “The highest point of the watershed is Nogales, Sonora, and the lowest is Nogales, Arizona,” Marruffo explains. “So everything, by gravity, flows from south to north. Everything that starts on the top of the watershed is going to drain down to the US side.”

Seeking to build upon decades of cross-border cooperation on stormwater management and water quality issues, officials and representatives from both sides of the border last year participated in a two-day Growing Water Smart workshop organized by the Sonoran Institute and the Lincoln Institute’s Babbitt Center for Land and Water Policy.

Growing Water Smart is a training and assistance program for local leaders that focuses on water and land use integration. The goal is to help officials identify and implement near-term plans, policies, and programs to achieve more resilient communities.

A major piece of the program is a multiday in-person workshop that brings together local and regional elected officials, water resource managers, economic development staff, sustainability officers, and planning commissioners, among others, who don’t always get to coordinate their efforts or pool their knowledge despite their shared goals. “It’s really about allowing them to discuss the issues and opportunities that are unique to them and to their context, and then supporting them with tools and facilitating good guidance,” says Noah Kaiser, Growing Water Smart program manager at the Sonoran Institute.

But the program is more than just a one-off workshop: The Sonoran Institute provides follow-up assistance to help communities secure funding and support project development.

Marruffo, who attended the Ambos Nogales workshop in June 2024, says the strong regional reputation of the Sonoran Institute brought credibility to the discussions, and that the ongoing support will help ensure that momentum doesn’t wane. “They’re probably one of the strongest collaborators that we have to address water issues, especially for the Santa Cruz River,” he says, which flows from Arizona into Mexico and back again.

The workshop “was a great opportunity to have a mix of different sectors involved from both sides, which is not easy to accomplish, getting local governments to speak face-to-face on the same problems,” Marruffo says. He felt encouraged by a new willingness on both sides of the border to make investments in Sonora, in whose steep and hastily settled hillsides most of the area’s stormwater issues originate.

“Every major artery or road in the city of Nogales, Sonora, aligns perfectly with the washes [or stormwater channels],” Marruffo says. “So in storm events, the roads become rivers or streams.” Many roads are unpaved, so fast-flowing stormwater gathers sediment that scours away aging concrete infrastructure and clogs sewers, sending raw sewage into the waterways.

“If you want to mitigate the problem, there are many things that you can do. But to really solve the issue, you have to start by addressing the origin,” Marruffo says. “So the narrative started evolving: What type of investment do we need in Mexico? Which are the major infrastructure projects? Where should we locate these projects?”

Working with a comprehensive green infrastructure plan for the Ambos Nogales watershed developed by Arizona State University Professor Francisco Lara-Valencia, the group discussed the kinds of interventions needed to further mitigate stormwater impacts, Marruffo says, such as building retention and detention basins in the upper watershed to reduce the energy of flowing runoff and help with infiltration.

These aren’t new ideas for the region; local, state, and federal agencies have been working on these very issues for years. Indeed, Marruffo says, “It’s part of our daily conversations.” But the efforts made on one side of the border often have little connection to those on the other side, and vice versa. “This is the first binational, holistic, comprehensive master plan that includes the whole watershed,” he says.

“There are a lot of people in the region working on this stuff,” Kaiser agrees. But getting them all rowing in the same direction can make their efforts that much more effective, he notes. Cross-border and interagency cooperation is crucial when it comes to practical matters, like installing green infrastructure such as rain gardens and retention walls to reduce the impacts of flooding. But it also lays a foundation for exploring what’s possible—like whether the two cities can see this challenge as an opportunity, perhaps capturing stormwater for reuse.

A few months after the Ambos Nogales workshop, the Sonoran Institute and Babbitt Center hosted a second, similar Growing Water Smart program in Mexicali-Calexico, where southeast California borders Baja California. “In the Mexicali-Calexico region, the New River, which flows from Mexicali northward into Calexico and into the United States, is an extremely polluted river,” Kaiser says. “So a lot of our conversations at the workshop in Mexicali revolved around, How do we manage this river on both sides of the border? How do we improve its water quality? How do we make it a valuable water resource for communities on both sides of the border?’”

These border community workshops marked a new international milestone for the Growing Water Smart program (and required a few adaptations, Kaiser says, such as bilingual facilitators and curriculum materials). The program began in Colorado in 2017, and later expanded to Arizona, Utah, and California.

While the program helps communities think about their long-term water resiliency, “it also helps them get momentum right away with some immediate actions,” says Kristen Keener Busby, associate director of program implementation at the Babbitt Center. In addition to guiding land use professionals and water managers through the carefully curated curriculum and facilitated dialogue, she notes, “it sets them up with some strategic planning they can implement right away.”

All Growing Water Smart workshops focus on creating a near-term 12- to 18-month action plan that aligns with a community’s realistic capacity; this is a physical document that community leaders can take with them, Kaiser explains. “We don’t want the workshop to be just another conference that they’re attending where they hear some panel information, and they have some conversations, and then they go back to work and nothing changes,” he says. “We want them to develop a tool that they can move forward with.”

One of the final working sessions is dedicated to action planning, with an in-depth exploration of funding sources, in-kind opportunities, and grants that teams can apply to. The aim is to help teams decide what they’re going to do, how they’re going to fund it, and other practical logistics. “What resources do we need? Which agencies are going to lead, which are going to support? Which other agencies do we need to keep apprised of what we’re doing? Who do we need to collaborate with? All those details go into the action plan,” Kaiser says.

“And we as facilitators from Sonoran Institute, Babbitt Center, and other partner agencies, we’re not deciding what that looks like,” Kaiser adds. “The point of the action plan is really for them to be able to take charge of it, and not to be assigned work to do, but to make their own decisions about what do we have capacity for? What is meaningful and makes the most sense to us, and how can we push that forward?”

The next US–MX Border Growing Water Smart event is a one-day convening in June, focusing on the cross-border sister cities of Douglas, Arizona, and Agua Prieta, Sonora.

After all, stormwater and contaminants don’t care about national boundaries, and need no visa to enter the US, Marruffa says. “So it’s fundamental to continue engaging between both countries. I think it’s important that we have these types of conversations and dialogue, because that’s the only way we can strategize and make better use of our resources, on both sides,” he says.

“There are asymmetries and disparities in many ways, socioeconomic and political. But I think these types of opportunities to talk face-to-face with partners, from both sides, always have positive results. Always, something happens that is one step forward.”

Jon Gorey is a staff writer at the Lincoln Institute of Land Policy.

Lead image: The cities of Nogales, Sonora, and Nogales, Arizona, form the metro area known as Ambos Nogales. Credit: USGS.