Conservation Matters June 2012

The Texas Land, Water and Wildlife Connection

Researcher says lessons from the Ogallala could help save Mexico's Calera Aquifer

By Alejandra Arreola-Triana

Dr. Francisco Mojarro, a researcher from the Autonomous University of Zacatecas in Mexico, is trying to find a way to save the Calera Aquifer, which is located in central Mexico. The most valuable source of drinking water in the region, the aquifer's continuous exploitation and low recharge rate is causing the groundwater level to decline at an unsustainable rate, Mojarro said.

"It is clear that the solution to arrive at sustainable exploitation of the Calera Aquifer will require more than switching to a better irrigation system and crops with lower water requirements," said Mojarro at a June 22 seminar on the Texas A&M University campus.

Mojarro used the Soil and Water Assessment Tool (SWAT) to assess the vulnerability of the aquifer and simulate different water conservation scenarios.  

Mojarro has been working with scientists in the USDA Agricultural Research Service's Ogallala Aquifer Program since 2007 to design water-conserving scenarios for the Calera Aquifer. "We used the Ogallala platform because there are many similarities between the aquifers," Mojarro said.

The Calera and Ogallala aquifers have similar hydrologic characteristics, and their water is used in similar ways, Mojarro said. Just like in the Ogallala, most of the water pumped from the Calera Aquifer--approximately 80 percent--is used to irrigate crops, and 13 percent is used to provide drinking water to urban centers, including Zacatecas, the capital of the state of Zacatecas.

According to CONAGUA, the Mexican Water Commission, the Calera Aquifer is being depleted at a rate of 0.4 to 1.5 meters per year. Additionally, only 3 percent of the water used is recharged to the aquifer. These conditions create a negative balance in the water budget.

One of the conservation scenarios discussed by Mojarro consists of changing from low-efficiency irrigation systems, such as furrows, to high-efficiency irrigation systems, such as sprinklers and drip irrigation. Another scenario consists of changing the types of crops grown in the region, from red beans, chile and garlic to canola and other crops with lower irrigation requirements.

But switching to high-efficiency crops and irrigation systems is not enough, Mojarro said. To conserve the maximum amount of water in the aquifer, he suggested that some crops, such as corn and beans, be replaced with native grasses. According to Mojarro, the benefits of a change in land use from agriculture to rangeland will include a reduction of surface runoff and erosion and an increase in water recharge.

Mojarro said that the next step in the project involves farmers in the Calera Aquifer region using a technology used in the Ogallala region. "Each farmer who has a cell phone will receive a message telling him how much water to apply depending on the type of crop," he said.

The seminar, "A Decision Support System for the Sustainability of the Calera Aquifer in Zacatecas, Mexico," was jointly hosted by the Texas Water Resources Institute and the Texas A&M Department of Biological and Agricultural Engineering.

Watch the seminar on YouTube.                                  

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