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Constructed wetlands and rainwater harvesting systems

By IW:LEARN

September 26^th, 2025

The indigenous communities of Yaxley, San Antonio Segundo, and Yodzonot Nuevo share not only the scenic beauty of Mexico's Caribbean coast, its customs, and way of life, but they have also experienced common challenges in water and sanitation. Paradoxically, water surrounds them; their proximity to the ocean and the Sian Ka'an reserve contrasts with the lack of water for everyday use, a common element of daily life.

In response to these challenges, solutions involve building community capacity for decision-making in the management of local water resources and the maintenance and operation of eco-technologies, which have been successfully implemented in previous community interventions to ensure their long-term functionality.

In the Mayan communities of San Antonio Segundo and Yaxley, six wetlands were constructed at the household level, one wetland per family. Additionally, a community wetland was constructed. Six rainwater harvesting systems were also rehabilitated, benefiting six families, each consisting of approximately five members.

Sian Ka'an, Quintana Roo, Mexico. Photo: Dan Mall/Unsplash.

Interview with Irving Olvera, Department Head, Sub-Directorate of Technical and Regulatory Support in Cost Engineering at CONAGUA, with contributions from Friends of Sian Ka'an:

What is a constructed wetland?

It is an alternative water treatment system that eliminates or reduces pollutants through natural processes involving aquatic life (macrophytic plants), filter media (sand, gravel, charcoal, rock), and microorganisms that biologically degrade pollutants.

This type of wetland treats residential wastewater, particularly graywater (from the kitchen, laundry room, sink, and shower), through natural processes for domestic reuse, irrigation, or infiltration, preventing soil and aquifer contamination.

What is a rainwater harvesting system?

Rainwater harvesting systems are technologies that create a catchment area in homes to collect rainwater. It is then channelled to storage locations, such as cisterns or storage tanks, where it is treated appropriately for human use and consumption.

They involve capturing rainwater that runs through a roof or surface into a gutter system, where it is filtered through a metal mesh, preventing leaves, branches, dirt, and other solids from entering the pipes. These pipes will channel the collected water to a storage container, where a disinfection method (such as chlorination) will be applied to eliminate microorganisms. A household inlet will be installed at the outlet of the storage container, accompanied by a hand pump for distribution to the home. Finally, a purification treatment using microfiltration technology will be applied to meet the water quality requirements for human consumption.

Rainwater can be used for domestic use, human consumption, agricultural use and livestock use.

What recommendations are there for rainwater harvesting?

Once a year, at the end of the dry season and the start of the rainy season, clean the roof or catchment area, gutters, downspouts, and the top of the storage tank, which will also be used as a catchment area.

Once every two years, at the end of the dry season and the start of the rainy season, when the storage tank level is at its lowest, all the water should be emptied and collected in other containers for later use, carrying out cleaning actions such as:

Every six months or when necessary, check for leaks and, if necessary, repair them by sealing them.
At the beginning of each month, clean the areas near the storage tank, removing weeds and other materials that could become breeding grounds for contaminants.
At the beginning of each week, check the catchment system for insects or small animals and, if necessary, remove them.
Constantly prune trees or plants around the roof or surface where rainwater is collected to prevent the presence of branches, leaves, and animals.

What impact does this intervention have on the Integrated Water Resource Management objectives?

The project enables us to strengthen the conservation of local water resources and consolidate water governance through community engagement and technical support. Furthermore, it promotes participation and ownership by the families involved in the efficient use and management of water.

About the project

GEF CReW+: An integrated approach to water and wastewater management using innovative solutions and promoting financing mechanisms in the Wider Caribbean Region, is a partnership project funded by the Global Environment Facility (GEF) that is being co-implemented by the Inter-American Development Bank (IDB) and the United Nations Environment Programme (UNEP) in 18 countries of the Wider Caribbean Region (WCR). This project builds upon its previous successful phase “The Caribbean Regional Fund for Wastewater Management (CReW)” project (2011-2017). GEF CReW+ is being executed by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH, the Organisation of the American States (OAS) and the Secretariat of the Cartagena Convention (CAR/RCU) on behalf of the IDB and UNEP respectively.