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Ana Castaneda - Himmelspach

Meeting the needs of water management in Mexico City with pre Hispanic cultures practices

Mexico City is the country’s capital with a population of 8.8 million. Along history, the city has gone through major environment transformations and is now facing water scarcity. Its main freshwater source is the groundwater from the Mexico’s aquifer. This source is currently over exploited. The major demand sector is the domestic, representing 89% of the total.

The aim of this research is to examine the current scarcity situation and the environmental changes in the region. Also, to identify the main pre Hispanic water management practices that can be applied in the current Mexico City’s context. Then to evaluate, with the WEAP mass water balance, the feasibility of applying one pre Hispanic technology.  Lastly, to recommend alternatives for making the technology attractive.

Some pre Hispanic cultures used rainwater to fulfil their domestic water needs. They deployed two practices: building large reservoirs to provide water for the community and by constructing residential cisterns. Rainwater harvesting is the ancient practice that can be applied in the current Mexico City’s context to diminish the aquifer’s withdrawal. Its application can be in apartment buildings with a capture rate of 19% of the total consumption, which accounts for 1.17 m3/second of the precipitation flow. This is still not enough to overcome the over exploitation of the aquifer, since the extracted volume is still more than its recharge. The local authorities have developed a plan for recharging the aquifer through infiltration wells and only consider rainwater harvesting for domestic use in rural areas. There are fiscal incentives that the government can apply to support the rainwater harvesting technology to withdraw less from the aquifer and diminish its over exploitation.