Sustainable Utilization of the Calera Aquifer, Zacatecas, Mexico

Groundwater extraction from the Calera Aquifer in the State of Zacatecas, Mexico, for irrigation, urban, and industrial uses has increased over recent decades to unsustainable levels. The annual groundwater deficit was estimated to be 172.5 (10(6)m(3) /yr) and groundwater table elevation to drop by 1.15 (m) per year. Irrigated agriculture used about 84% [207.6 (10(6)m(3) /yr)] of total extracted groundwater, urban 10% [24.1 (10(6)m(3) /yr)], and industry 6% [15.4 (10(6)m(3) /yr)]. An annual, watershed-scale water budget analysis was conducted to evaluate alternative water management and conservation scenarios and determine their effectiveness at slowing the rate of groundwater depletion. The most restrictive scenario called for a 10% reduction in industrial and urban water use and a 50% reduction in irrigation water in the first decade after year 2015, and an additional 10% reduction in irrigation water every decade after year 2025. According to this latter scenario, annual groundwater deficit would decrease to 45.5 (10(6)m(3) /yr) by year 2045, groundwater table would be 18.1 (m) lower than that in year 2015, and groundwater table elevation would drop 0.3 (m) per year. The 50% reduction in irrigation water was achieved by upgrading inefficient surface irrigation to sprinkler and drip irrigation; converting under-performing crops (oats and maize) to rain fed cropland; switching 30% of the irrigated dry bean crop to canola, a more water efficient crop; and, taking 15% of onion, garlic, and red pepper crops out of irrigated production. Additional cropland will have to be taken out of irrigation to meet water use targets set for 2035 and 2045. This water management scenario would extend the useful life of the aquifer and represents a great improvement over current unsustainable groundwater extraction. However, curtailing irrigated agriculture to a point where profitable crops must be taken out of production may not be an acceptable solution from a political and socio-economic standpoint because it would greatly impact the region’s agricultural economy.