Mexico City faces an alarming water crisis, and the water shortages there may very well reflect the woes of the global freshwater supply question. 40 percent of the planet does not have access to clean water or sanitation.
Mexico City has a population that exceeds 19 million people. The Mexican capitol was built on the bed of a lake, an vast extension of humanity - the third largest metropolitan conglomerate in the world - that originated from the Aztec empire.
Modern-day Mexico City faces a water shortage - exacerbated by recent weather patterns - that has inspired an advertising campaign from the government: "February 2010: The City May Run Out of Water."
While the immediate water shortage in Mexico City has been attributed to weather patterns in the Pacific Ocean, the issue of water scarcity is more reflective of an unsustainable population's demand pitted against an increasingly limited supply.
This equation is not limited to footprint of Mexico City. It is a global equation.
According to the World Bank, 80 countries are now experiencing water shortages severe enough to have an impact on the health and economic output of their populations. 2 billion people - roughly 40 percent of the worldwide population - do not have access to clean drinking water or sanitation.
With a global population that currently requires 1.3 earths to sustain, water shortage should not be a surprise. But as water supplies dwindle - where, in many cases (Middle East, Africa) a single water source is shared by two or more antagonistic nations - it is expected that the scarcity will result in diplomatic pressures and in open conflict.
The water scarcity issue is likely most dramatic in China, where the water table drops one meter a year due to the needs of a far too large population.
Water shortages also exist in the United States, particularly in western and southeastern states.
There are a few technical solutions - ranging from water recycling and desalination to cloud seeding - but while these solutions do hold good promise they should likely be coupled with family planning education and implementation the balance the crushing weight of the human overpopulation impact.
In the meantime, large cities like Mexico City, Los Angeles and Beijing will have to rely on common sense conservation practices and trust that their populations will comply.