Construction of Wetlands in La Piedad Lagoon
Fabiola Sosa-Rodriguez
Metropolitan Autonomous University, Mexico
Winning article: Construction of wetlands in La Piedad Lagoon: a strategy to mitigate climate change in Mexico (Blue-Green Systems, 2024)
“This initiative underscores the urgent need for holistic, cross-disciplinary collaboration in solving the global water crisis.”
Restoring and safeguarding freshwater ecosystems through integrated and multifaceted approaches is critical for maintaining freshwater use within the planet's ecological boundaries. This not only ensures the sustainable and equitable availability of water but also cultivates meaningful engagement across communities, industries, and policymakers. The growing threat of climate change is exacerbating water scarcity, amplifying pressures on food security, economic resilience, and public health systems.
Figure 1: Image taken of La Piedad Lagoon by Alan Nava (co-author), 2024
Mexico's Water Crisis and Climate Change
Mexico is highly vulnerable to the impacts of climate change and is already experiencing significant water stress. Many cities face an imminent ‘Day Zero’, a critical point in water scarcity when an accessible, reliable freshwater supply runs out. Climate models predict that water availability in Mexico could decline by 30% between 2075 and 2099, while in the Mexico City Metropolitan Area (MCMA), home to 22 million people, the reduction could reach 40%. This situation threatens water access, food security, and biodiversity, with potential economic losses exceeding 20% of the region's GDP. Furthermore, poor water management and the lack of wastewater treatment have exacerbated the crisis, severely contaminating water bodies and reducing water availability. Our research aims to enhance the development and implementation of adaptive strategies to mitigate these issues in collaboration with authorities, the private sector, and local communities.
La Piedad Lagoon Project: A Nature-Based Solution
Since 2003, La Piedad Lagoon, located in the MCMA, has been contaminated with 150 L/s of wastewater from domestic, agricultural, and industrial sources, forcing local farmers (ejidatarios) to abandon fishing and farming. The Lagoon spans 34 hectares and possesses a storage capacity of 2 million m³ per year. Historically, the Huilango and Tepojaco ejidos depended on the Lagoon for food production and commercial fishing, but its degradation has destroyed their livelihoods.
Access to water in the region has become increasingly complex due to the overexploitation of regional water sources, such as the Cuautitlan-Pachuca aquifer (depleted by 189 million m³ per year) and the Cutzamala System. Ineffective water management, compounded by the impacts of climate change, has dramatically decreased water availability, jeopardizing both human health and ecosystem stability. By 2030, the region is expected to grow by an additional 200,000 residents, leading to a 22 million m³ increase in water demand and a 17 million m³ rise in wastewater generation, exacerbating existing pressures and conflicts associated with water accessibility.
Despite severe pollution, La Piedad Lagoon remains an ecological hotspot, hosting 1,500 documented species, some at risk. The presence of this great variety of species in the Lagoon, despite its levels of contamination, is testament to the environmental relevance of the area and the contribution that its recovery would have on the regional ecological functions.
An eight-year intervention has been conducted to address urgent water management issues at La Piedad Lagoon. This project centers on Nature-Based Solutions (NbS), aiming to enhance water resilience and provide a new water source for 1.2 million people in the surrounding communities. The Lagoon was chosen due to its high potential for wetland restoration, as indicated by hydrological balance assessments.
The project includes a comprehensive water treatment system featuring a 1.5 km biofiltration corridor to treat inflowing water, and constructed wetlands to remove various pollutants, primarily biodegradable compounds, some metals, and recalcitrant organic compounds. This system will incorporate subsurface wetlands that function via gravity and 20 productive floating wetlands to enhance biological filtration and promote new economic activities that encourage community engagement with this NbS. The infrastructure will also feature a filtration system utilizing activated carbon and silica sand to remove bacteria, viruses, and minerals (including particles with different characteristics), and an Advanced Oxidation Process (AOP), reliant on the catalytic decomposition of ozone, to produce drinking water.
This project is a pioneering example of sustainable wastewater treatment, filtration, and reuse, aligning water resource management with planetary boundaries. It also contributes to ecosystem restoration, enhances local biodiversity, and reduces health risks associated with inadequate sanitation. Using advanced post-treatment methods like oxidation and metal sorption, La Piedad Lagoon can become a safe alternative water source for human consumption and irrigation. This approach sets a national precedent for water reuse that can be replicated in various cities. Furthermore, it challenges the current water paradigm, which relies on transporting water from distant sources at high costs and often leads to the disposal of wastewater without proper treatment or reuse. Undoubtedly, this initiative will help maintain freshwater use within safe operational limits on our planet. Implementing such interventions necessitates transdisciplinary research, where scientific knowledge is translated into effective public policies for more sustainable water management. Universities have a crucial role to play in paving this solution.
Proposal of a Novel Water Management Model through Transdisciplinary Research
The La Piedad Lagoon restoration project is Mexico's first initiative of its kind, incorporating several innovative approaches aimed at addressing environmental and societal challenges. At its core, the project emphasizes the co-design and co-construction of interventions alongside local communities, ensuring that the people directly affected by the lagoon’s restoration play a key role in its success. The initiative also seeks to develop a new urban-rural water management model for climate adaptation, integrating citizen science to empower communities in monitoring biodiversity and water quality. This approach not only enhances community involvement but also equips members with the skills needed to create and maintain wetlands, showcasing that Nature-based Solutions (NbS) can be implemented by all and easily replicated across the country. The project further incorporates the reintroduction of traditional agroecological practices, such as chinampas, which aim to improve biological connectivity, enhance water quality, generate sustainable income through high-value flower cultivation, and provide emergency water reserves for the Metropolitan Area of Mexico City (MCMA)—a vital strategy for climate adaptation. Additionally, the project features the first synergistic treatment system, combining constructed wetlands with advanced oxidation processes (AOP), to create a new drinking water source, addressing the growing water crisis in the MCMA. Overall, La Piedad Lagoon project aims to transform the current water management paradigm by restoring functional ecosystems, while also improving water quality, enhancing climate resilience, and elevating the quality of life for local communities.
Economic and Social Integration: A Key to Success
A key lesson from this project is that successful water restoration requires both economic and social integration. Without active community participation and economic incentives, interventions are unlikely to achieve long-term sustainability. To ensure the engagement of critical stakeholders, the project has focused on developing new economic activities with local communities, such as flower farming, sustainable fishing, eco-tourism, and ecosystem services payments. Additionally, a watershed committee was established in 2023 to guarantee the inclusion of vulnerable groups in decision-making processes. The project also emphasizes the importance of monitoring the efficiency of Nature-based Solutions (NbS), identifying the most effective pollutant removal strategies that are not only suitable for the region but also cost-effective in terms of maintenance.
Scaling Up: Training Future Generations and Guiding Water Policy
Since 2023, the Educational Partnerships for Innovation in Communities (EPIC) Program has been integrated into the project, promoting capacity building through student engagement. Over 700 students from 15 disciplines have been trained in water bodies restoration based on a transdisciplinary perspective, forming the next generation of scientists, environmental defenders, and leaders. This program unites the human capital of the most important universities in Mexico with local, state, and federal governments and communities to attack the most pressing water challenges faced by local communities, fostering the co-construction and implementation of transformative solutions.
The La Piedad Lagoon restoration project serves as a scalable, community-driven model for achieving water security within planetary boundaries. By integrating Nature-based Solutions (NbS), scientific research, local governance, and economic development, the project offers a replicable approach for restoring degraded water bodies worldwide. It has successfully bridged the gap between science, policy, and community engagement, positioning the University as a vital facilitator in connecting local communities with governmental and private stakeholders to find common solutions, translating scientific knowledge into effective public policies, and providing a model for scaling up water body restoration efforts in Mexico and beyond.
This initiative underscores the urgent need for holistic, cross-disciplinary collaboration in solving the global water crisis. Its success highlights the role of citizen participation, traditional knowledge, and cutting-edge research in restoring ecosystems, enhancing climate resilience, and securing water resources for future generations.
Figure 2: The research team.