Towards a Water Sensitive Mexico City

This report offers a holistic vision that shows how public space interventions may serve as water infrastructure while part transforming public spaces for the enjoyment of Mexico City inhabitants.

In this way, public investments in infrastructure and urban projects can be maximized, fostering the regional, metropolitan and global competitiveness of Mexico City. It can be used as an example of best practices in sustainability and resilience as well as social and urban development.

The Public Space Authority (in Spanish Autoridad del Espacio Público; AEP) of the Mexico City government recognizes cyclical flooding and water shortages as some of the most pressing urban vulnerabilities in the City.

In figuring out how to tackle the water paradox using public space, the AEP used Rotterdam’s water plazas as an example. At the regional scale, water plazas could redistribute wealth thorough the City and mitigate water-related vulnerabilities. At the local scale, they help reconstruct the City’s broken relationship with water. The AEP aims to combine quality public space with water management strategies, in order to create a more sustainable city.

Runoff that recharges the aquifer has decreased due to deforestation in the mountains.

Vegetation performs an important role in delaying and retaining rainwater by decreasing the runoff speed and volume, and distributing it more evenly along the slopes on the hills, allowing the rainwater to infiltrate. Deforestation increases the runoff volume that has to be absorbed by the subterranean drainage system, causing flash floods in the foothills.

It is critical to reduce water demand in Mexico City.

Key parts of the hydrological balance are identified where public space projects could mitigate water-related vulnerabilities. The consequences of these projects would mostly be direct effects, like decreasing the runoff volume or increasing the recharge rate of the aquifer. However, in some cases there would also be indirect effects, such as decreasing the need to import water from other watersheds.

The main goal within the Conservation Soil for a Water Sensitive Mexico City is to maximize conservation in order to maximize water infiltration to the aquifer.

This vast and undeveloped area has a great infiltration potential due to the porous structure of the volcanic rock. However, deforestation of the slopes over the last decades has led to large volumes of runoff, with little retention during rainfall events.

Interestingly, the areas with the highest potential to recharge the aquifer overlap with areas subject to environmental protection, conservation and restoration, such as the official Conservation Area to the South of Mexico City.

The goal in the foothills is to minimize the rainfall runoff speed and volume in order to prevent flash flooding downstream.

The foothills are the transition between the mountains and the low, urbanized basin. Water that flows down from the mountains is hardly being slowed down, as a large portion of these slopes become more (partly illegally) urbanized. Paving of large surfaces further accelerates the runoff.

Among the main strategies for decreasing the runoff are small dams or natural obstacles that temporarily retain the water in public spaces. This would provide time for the water to infiltrate in a natural way.

As in the Zone 2, the objective along the Lahar slopes would be to minimize runoff speed and volume in order to prevent flash flooding downstream.

After slowing down the runoff, the water could be reused or drained. As this area is highly urbanized, the runoff is concentrated in a few streams that can reach dangerous speeds, causing significant landside risk. The main strategy is to temporarily retain the water and substantially decrease its speed.

The Western side of the Basin, where the disappeared freshwater lake was located, represents the current paradox of Mexico City’s relationship with water. Here, floods resulting from heavy rains and drought problems caused by water scarcity and strong heat waves overlap. This is also the area of the City that has been urbanised for a longer period of time and has the highest population density.

Interventions in this zone have to capture the water in times of heavy rainfall and then reuse it during the dry periods. A series of interventions that fit into the dense urban fabric should be used, such as floodable infrastructure, water plazas, roadside bioswales, and lush green raingardens. This approach results in a network of small scale public spaces and hosts a diversity of urban uses.

The main objective in the Eastern part of the Basin, where the disappeared saltwater lake was located, is to combat drought and its consequences.

This zone presents an accumulation of severe problems caused by heat waves, including high evapotranspiration rates and a lack of drinking water. Many wells extract water constantly from the aquifer, which exacerbates subsidence.

The main strategy is to store water during the rainy season and reuse it during the long dry season. Water can also be reused by individuals or local communities in order to reduce dependence on the public supply and reduce groundwater extraction and subsequent subsidence.

The objective in Xochimilco is to save and restore a highly valuable cultural and environmental heritage.

This is the only remaining pre-Hispanic agricultural landscape within Mexico City that showcases the ancient harmony the Mexica reached between water and urbanisation.

The main strategies include improving water quality by implementing a basic and adequate sewage infrastructure, expanding the lakes and canals in order to maximize seasonal storage and increasing the areas of ecological and cultural protection (Conservation Soil).