Aquatic systems and water security in the Metropolitan Valley of Mexico City

In megacities water quantity and quality are threatened by complex and interrelated processes caused by population growth, land use change, unsustainable agricultural practices, deforestation, erosion, destruction of ecosystems, lack of planning, laissez-faire policies, unsustainable water management, political conflicts, and increasingly also by the impacts of climate change. In the Metropolitan Valley of Mexico City (MVMC) located in the high plateau of Mexico City and on former lakes, the dry out policies during the last 300 years have been counterproductive, causing scarcity, pollution, health and environmental problems, subsidence and water conflicts, particularly affecting social vulnerable people.Megacities require an integrated management of water and aquatic systems — integral water resource management, rainwater harvesting, maintenance and replacement of infrastructure, restoration of ecosystems and urban planning. This implies investments and a water culture including a transparent administration and peaceful negotiation of conflicts regarding concessions, access, and reuse of water allocation. Socio-political and environmental processes are complex; besides technical factors and ecosystem recovery, socio-cultural changes must transform human settlements and power structures.

► Water security promotes the restoration of aquatic systems through sustainable development, political stability and protection of humans from water-related hazards.
► Unsustainable water management in megacities is critical for citizens, but especially for slum dwellers, threatened by lack of safe water, subsidence, and in the case of Mexico City sewage flooding.
► Overexploitation of aquifers as a result of increasing demand due to population growth and inadequate supply factors represents health risks to humans given dissolved minerals.
► Recovering aquatic systems includes ecosystems restoration, rainwater harvesting, and sewage treatment plants with slow infiltration for recharging overexploited aquifers.
► Tariffs must reflect real costs of investment, maintenance, groundwater pumping or water importing from other basins, thus obliging consumers to reduce, reuse and recycle water.
► Subsidies send wrong signals to consumers about water crisis and promote waste of water.