Summary: Mexico City has short-term water problems and long-term water problems.

The amount of water delivered to Mexico City from reservoirs in its supply system will be cut by 10% over the summer, because of lower than normal rainfall, according to a report by Ricardo Rivera in Reforma. (Subscription required) The fall in the reservoir levels has already caused some of the water delivered to some areas of the city to have an unpleasant odor and taste. Although the water authorities maintain the water is safe, other experts urge caution, and are recommending the use of bottled water. The journal Esquema writing about Mexico City’s water quality says:

Mientras el agua puede estar disponible en cantidades adecuadas (aunque esto no siempre sucede), existe desconfianza, a veces bien fundada, sobre su calidad. No es infrecuente que para cumplir con las funciones de alimentación el agua se hierva, se desinfecte o, de plano, el consumidor acuda al agua purificada y embotellada.

[While water may be available in adequate amounts (although that doesn't always happen), there exists a lack of confidence, at times well founded, in its quality. Not infrequently water is boiled, disinfected, or is simply purchased bottled and purified  for food preparation.]

Because of this, since 2007, Mexico City has had the highest consumption of bottled water on the planet — about 240 liters per person per year.

Mexico City gets water from the giant basin in which it sits, which was once the site of great lakes. Tenochtitlán, the city that greeted Cortez when he arrived, was built into Lake Texcoco. Most of those lakes have disappeared, and only tiny remnants like the current Xochimilco remain. The water that fed them, however, is still captured, and diverted into the city’s water supply. Other sources are in Michoacán, in springs in the area, and in underground aquifers. Some of the water comes from as far away as two hundred kilometers. The supply has barely kept pace with burgeoning demand, in a city which has grown to 20 million inhabitants, and is still a top destination for Mexicans leaving the land. Both variable rainfall and possible effects of climate change affect the recharge of the aquifers, and currently that withdrawal of water from the aquifers is already greater than their recharge.

Another difficulty that the water system in Mexico City faces is leakage, sometimes a bit disingenuously called “unaccounted-for water.” This is a well-known issue in all water systems, and one that they constantly battle. X amount of water goes into the system, and Y is measured at the point of consumption. Y is always less than X. Most often it is due to leaks, but sometimes also to unauthorized or unpaid use. The 1995 license for Sydney Water in Sydney, Australia, required it reduce unaccounted-for water to a maximum of 15 percent. (Water International, V. 24, No. 4, p. 357, Dec. 1999) New York City has about 3 percent; Singapore 5 percent. Lagos, Nigeria, has 96 percent. In Mexico City, leakage amounts to something like 40 percent according to Esquema (although Wikipedia puts it at 51 percent). That presents a lot of opportunity to increase the water reaching customers without increasing the amount injected into the system: Plug the leaks. It’s a very costly proposition, however.

Another issue constantly under discussion is changing the amounts drawn from the system. In the current short-term shortage in Mexico City, the plan is to ration water among the boroughs (delegaciones). But often the talk turns to pricing. And at that point, people start to get into a real lather. One reason is the perception of the conversion of a right — everyone must have a certain amount of water — to a commodity. That in itself is politically charged. Pricing requires at the very least metering of water usage, which can also be highly contentious. In spite of a 1992 Federal requirement in the United States for water metering in California, in 2009 half the residents of the Central Valley — a  true desert in geographic terms — did not have water meters, and were going to fight this imposition to the death. Or maybe not. Cities with meters use about 15 percent less water, in California’s case. Communities can reconcile a right to water and the pricing issue. In the case of the city where I live, the first tranche of water usage is charged at a very low rate (and it could be free); costs step up with increasing usage after that.

The discussion about infrastructure improvements (i.e., plugging leaks), metering and pricing is often accompanied by the proposal for privatization. (Just to be clear, it doesn’t have to involve privatization. Where I live, water is distributed by the city.) That has been bruited about in Mexico City, and it is highly contentious. There are some private water entities in some boroughs and in other Mexican cities, but the system is still evolving.