The Tijuana River watershed, which spans the US-Mexico border, faces long-standing environmental and public health challenges due to persistent pollution. Over 2.8 million people rely on the resources of the Tijuana River every day, but the insufficient wastewater treatment infrastructure has caused the river to become an environmental hazard impacting public health and local economies.

Through the 2024 World Design Capital, regional nonprofits Iniciativa Río Tijuana A.C. in Mexico and 4 Walls International in the United States joined forces with Arup to co-create a shared, publicly accessible visualization of the watershed. Bringing expertise in digital mapping, Arup established the tool requirements, conducted data integration, and led the tool development process. The resulting platform visualizes environmental needs and prioritizes interventions, enabling data-driven decision-making for nonprofits, agencies, and community groups on both sides of the border. 

The Tijuana River Index is designed to drive regional action through a shared, data-informed understanding of the watershed. By making environmental data more accessible and actionable, the tool supports education, investment, and collaboration across borders. It empowers local communities, nonprofits, and agencies to identify meaningful interventions, and take part in restoring the river’s health and resilience. 

This work was funded through Arup’s Community Engagement program, which enables us to contribute our expertise and skills to underserved communities through pro-bono work alongside charitable partners.

A river running through a grassy area.

The Tijuana River watershed, spanning the US-Mexico border, has faced environmental and public health challenges due to pollution

Seeking a local perspective 

The geospatial analysis tool, which was created by Arup and partners, draws upon digital mapping and local insight. As the technical lead, Arup designed and developed the tool, called the Tijuana River Index, to support environmental restoration efforts across the Tijuana River watershed. To inform the development of the Tijuana River Index, Arup led a series of engagement workshops with community members and nonprofit leaders from both sides of the border. These sessions helped identify five priority areas for intervention: waste cleanup, erosion reduction, revegetation and reforestation, access to green space, and decentralized wastewater treatment. This collaborative approach ensured that the tool reflected local knowledge and community priorities, grounding the platform in lived experience. 

The data-driven platform enables a better understanding of the watershed’s condition, identification of areas most in need of intervention, support for cross-border collaboration, and prioritization opportunities for funding and action. In 2024, the index was presented at San Diego Design Week to raise local awareness of the tool and connect directly with new users.  

A person giving a presentation to a group of people outdoors under a yellow tent

Arup presented the Tijuana River Index at San Diego Design Week 2024

Digital mapping and visualization 

Arup’s digital specialists led the development of the web-based platform that serves the foundation for the Tijuana River Index. Drawing on datasets from Mexico’s National Institute of Statistics and Geography, the country’s National Water Commission, the San Diego Association of Governments, and the California Open Data Portal, the tool aggregates information about the entire watershed together into one platform through ArcGIS. 

Beyond visualizing the watershed, the platform identifies environmental risks facing areas surrounding the Tijuana River. To build the index, Arup’s digital mapping experts used the tessellation tool in ArcGIS Pro to develop a hexagonal grid system. Each hexagon was assigned a score from 0 to 5 for each of the five priority areas of intervention identified during the stakeholder engagement phase. These scores were calculated using processed datasets via the Feature Manipulation Engine (FME) in ArcGIS. This spatial indexing system enables users to quickly identify areas of greatest need and supports targeted, data-driven action.  

User interface for hexagonal map of Tijuana River Index

Each hexagonal grid on the map is assigned a score from 0 to 5 for each of the priority areas of intervention 

User interface for hexagonal map of Tijuana River Index

Through data-driven insights, the index allows users to quickly identify areas in greatest need of support

The tool also enables site suitability analysis, which helps stakeholders identify high-need areas and align interventions with environmental and public health impact. This allows users to evaluate how different interventions might fare across varying scenarios. This approach also supports innovative funding mechanisms like environmental impact bonds, grants, or fundraising efforts, which tie success to measurable environmental outcomes.  

The index was created in ArcGIS Experience Builder and is visualized through an interactive dashboard. The resulting web-based platform serves as a centralized, open-access repository for watershed data visualized through an interactive dashboard. It offers users a seamless interface to explore regional needs and inform future intervention across the Tijuana River watershed.  

From project conception, the team's expertise, dedication, and collaborative spirit have been invaluable in advancing our shared goals for environmental sustainability and transboundary water management.” ​

Waylon Matson

4 Walls International

Partners & collaborators

4 Walls International / Iniciativa Río Tijuana