The provision and management of water resources is one of the most important areas related with Mexico City's environmental resilience. Dependence on external sources of supply, increased demand due to urbanisation, overexploitation of the aquifer, and inefficiencies in the water management system create a vulnerable situation, which is exacerbated by climate change's negative effects, such as increased water demand, degradation of catchment areas, and reduction in quality and recharge.

The natural availability of water in Mexico City is expected to decrease by 13 percent to 17 percent by 2050. Similarly, climate change can exacerbate current water infrastructure issues, such as lower rainfall, which is linked to supply cuts to ration consumption and ensure resource supply; or more intense rain, which exceeds the drainage system's discharge capacity, causing flooding and affecting mobility and public health.

Mexico City has developed its Local Climate Action Strategy (ELAC) 2020-2040 and Climate Action Programme of Mexico City (PACCM) 2020-2026, which will integrate climate policy cross-cutting and coordinated in the long, medium, and short term, helping to achieve the 2030 Agenda for Sustainable Development's Sustainable Development Goals and meeting the Paris Agreement's goals.

The ELAC and the PACCM work to reduce community vulnerability and adaptive capacity in the face of climate change effects (community-based adaptation – AbC); reduce risks and increase the resilience of strategic infrastructure and productive systems (adaptation based on disaster risk reduction – DRR); and conserve and sustainably use ecosystems and ecosystem services (ecosystem-based adaptation – AbE).

Rainwater harvesting systems ("Sistemas de Captación de Agua de Lluvia" (SCALL)) are a type of rainwater harvesting system that encourages the development and use of green technology, as well as water education and awareness, and ensures the involvement of the most vulnerable people. It also mitigates the harmful effects of flooding, ensures the human right to water and health, and promotes Mexico City's water security.

To install the SCALL, the city government is collaborating with Isla Urbana, a non-profit organisation that has been building harvesting equipment since 2009.

So far, more than 21,000 SCALLs have been installed in Mexico City's periphery. This translates into 870 million liters of water harvested every year and 130,000 users who directly benefit from rain water.

Over half a million people may survive for up to seven months without access to the metropolitan water infrastructure if the programme is effective.

Moreover, the effectiveness of this strategy could set a new precedent in urban governance, with whole areas of the city no longer depending on the government for daily access to this fundamental resource.

Photo by Oscar Reygo from Unsplash