Rainwater harvesting: An option to help solve Mexico City’s water crisis

Experts agree that Mexico City needs new policies, investments and measures to solve the capital’s worst ever water crisis, and a method to capture rainwater seems to be one of the most feasible solutions. 

“Harvesting rainwater offers a simple, practical, proven and inexpensive solution that could provide water for up to six months in areas such as homes and schools,” Eduardo Vázquez, executive director of Mexico City water fund Agua Capital, told BNamericas. 

“Rainwater harvesting is one of these solutions. It is viable and necessary. Every year, from May to October, billions of liters of water go down the drain and, what is worse, they cause severe flooding. Water is being wasted.”

According to the expert, whose organization last warned authorities about the consequences of not addressing the city’s water crisis in December, the fund helped design a program alongside NGO Isla Urbana to implement the necessary infrastructure to capture water in different parts of the city. 

Under mayor Claudia Sheinbaum, the city government has begun a program to install rainwater harvesting systems in households, providing 50% of the infrastructure’s financing. 

According to the 2021 operating manual that Mexico City’s environment department published in December, 477 neighborhoods in eight districts will benefit from the Cosecha de Lluvia program this year. 

The city has approved 200mn pesos (almost US$10mn) for subsidizing the systems this year, the same amount allocated to the program in 2020 and 2019. 

WATER CRISIS

Speaking at an international forum hosted by the United Nations on March 18, Sheinbaum acknowledged the water problems facing the city, especially in the urban area’s poorest neighborhoods. 

She cited three obstacles. The first is outdated and damaged infrastructure, which is to blame for leaks that cause up to 50% of water to be lost in some places; the second is the overexploitation of aquifers, linked to ground sinking issues; and the third is the adverse effects of climate change. 

“We know that at some point the issue of water will reach a point of collapse, a crisis which is due to many factors. One of them is obviously the concentration or increase in population density,” Anaid Velasco, researcher at the Mexican center for environmental rights (Cemda), told BNamericas. 

Velasco said the city’s infrastructure is in urgent need of modernization, given that leaks coming from the Lerma-Cutzamala water system are a major issue, especially when certain districts are suffering from service cuts. 

However, during the rainy season – when continuous rainfall can last up to 90 days – that water is wasted because the system lacks the infrastructure to store it, she said. 

Water authority Conagua reported in early March that the Lerma-Cutzamala distribution system, which supplies more than 30% of the water in the Valley of Mexico, had reached historic low levels. Another 12% comes from overexploited springs and 58% from the system’s aquifer.

The authority said at the time the system’s three main reservoirs were at 51.8%, the lowest level in two decades and 23% below what was reported during the same month 2019. 

This problem is mainly related to lack of rain, which is, at the same time, linked to global warming, Vázquez said. 

“This is no small issue. The scope of this drought has not been seen for more than 15 years and, with it, millions of people from multiple municipalities of Mexico state and Mexico City districts have been suffering from reduced water supply,” he said, referring to service cuts the local government announced in March. 

Mexico City, with almost 9mn residents, requires about 2.7Mm3 of water a day, or some 31,000 liters per second, Vázquez said, citing official figures.