The incredible shrinking aquifer - Ecocreto porous concrete

The incredible shrinking aquifer - ecological paving material called Ecocreto

"The incredible shrinking aquifer
BY ELIZA BARCLAY/The Herald Mexico, El Universal, Lunes 21 de febrero de 2005

For most Mexico City residents, the circulation of water is an obvious element of daily urban life, be it a projectile coursing down from the sky during the rainy months, a weekly task to replace or refill large plastic jugs of purified drinking water, or as a biweekly gift from the faucet for those marginalized communities whose utility service remains irregular.

As generations have built layer upon layer of structures to create the massive urban jungle that the city is today, it has become easy to forget that the city is sagging atop an enormous underground aquifer, where it has rested since the Aztecs built Tenochtitlan in the Valley of Mexico in the 14th century.

As the city's population has swelled to 18.5 million people, the pressure on the aquifer has become critical as the city's consumption of water has risen to 10,500 cubic feet per second, according to the city government's water division. Estimates of the aquifer's size and its ability to continue to sustain Mexico City vary considerably. Some local hydrologists say it could be fully depleted in as few as 10 to 20 years, while some government officials expect it to last 70 more years at minimum.

But the issue that is of concern to nearly everyone is insuring that the aquifer recharges properly as a means of avoiding full depletion. Though the city gets an average of 40 inches of rainfall per year, groundwater pumping exceeds the natural recharge by 50 to 80 percent. This overuse has resulted in declining groundwater levels, compression of the aquifer, subsidence of the land, and damage to buildings and other structures on the surface -- some parts of the Historic Center have dropped 30 feet.

An effort to recharge the aquifer has emerged from the private sector, in the form of an ecological paving material composed of aggregate grains that allow water to seep through straight into the ground. This porous concrete, called Ecocreto, has been employed in the construction of street pavement, sidewalks, parking lots, and bikepaths at more than 50 sites around the city, including the Televisa headquarters in Santa Fe and the National Museum of Antropology.

Developed by a team of Mexican engineers and architects in 1994 who were distressed by the looming water crises of Mexico City and Guadalajara, Ecocreto is similar to hydraulic concrete but manufactured without sand, which permits as much as 80 percent of rainwater to pass through into the subsoil.

"Our product is 100 percent permeable concrete additive that will help to recharge groundwater resources in Mexico and other parts of the world where water is scarce," said Néstor de Buen Unna, Ecocreto's general director. Ecocreto's popularity has bloomed in the past few years and the company now has distributors in Mexico, Canada and the United States.

Though initiatives like Martínez Santoyo's and Buen Unna's are steps forward in respecting the limits of the aquifer and finding ways to recharge it, the city still faces significant challenges in getting a grip on its water use. As the aquifer remains invisible to the eye above ground, it may be caught in losing tug-ofwar with the city's 18.5 million residents."

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