ARS | Publication request: Water budget considerations regarding groundwater extraction targets in the Calera Aquifer watershed, Mexico

Submitted to: Environmental and Water Resources Institute World Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 17, 2012
Publication Date: May 20, 2012
Citation: Garbrecht, J.D., Majorro, F., Echavarria, F., Bautista-Capetello, C., Steiner, J.L. 2012. Water budget considerations regarding groundwater extraction targets in the Calera Aquifer watershed, Mexico. In: Environmental and Water Resources Institute World Congress Proceedings, May 21-24, 2012, Albuquerque, New Mexico. 2012 CD-ROM.

Interpretive Summary: In regions with limited rainfall, communities rely on groundwater as their water source for agricultural, industrial and domestic water uses. Over time, as the communities grow, the demand for water increases and often exceeds the groundwater recharge capacity, thereby resulting in an unsustainable over-exploitation of the aquifer. The Calera Aquifer watershed in the State of Zacatecas, Mexico, did not escape this unfortunate but all too common reality. An annual, watershed-scale water budget analysis was conducted to identify alternative water conservation and water use scenarios, to determine their effectiveness at reducing groundwater extraction, and to project pathways towards a sustainable groundwater utilization. In all investigated scenarios, groundwater over-exploitation persisted and groundwater table continued to decline. All three sectors of the economy (agriculture, industry and urban) will have to implement water conservation practices to bring the aquifer over-exploitation under control. Agriculture was the largest water user and reductions in water use will likely involve a combination of higher irrigation efficiencies, introduction of low water-demand crops, reduction in number of existing irrigation wells, land conversions, deficit irrigation, and irrigation regulations. Even a scenario calling for a 50% reduction in irrigation water and an immediate moratorium on all new water allocation permits did not reduce the projected annual groundwater deficit to where a water balance between groundwater extraction and aquifer recharge is achieved. An annual aquifer depletion that is realistic and acceptable and that qualifies as sustainable utilization should be defined and used as target in evaluating alternative water budget scenarios.

Technical Abstract: 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. An annual, watershed-scale water budget analysis was conducted to identify alternative water conservation and water use scenarios, to determine their effectiveness at reducing groundwater extraction, and to project pathways towards a sustainable groundwater utilization. In all investigated scenarios, groundwater over-exploitation persisted and groundwater table continued to decline. All three sectors of the economy (agriculture, industry and urban) will have to implement water conservation practices to bring the aquifer over-exploitation under control. Agriculture was the largest water user and will likely see the largest reductions. But industrial and urban water demand is expected to continue to increase and will have to be part of the overall water conservation effort. In agriculture, reductions in water use will likely involve a combination of higher irrigation efficiencies, introduction of low water-demand crops, reduction in number of existing irrigation wells, land conversions, deficit irrigation, and irrigation regulations. Even a scenario calling for a 50% reduction in irrigation water and an immediate moratorium on all new water allocation permits did not reduce the projected annual groundwater deficit for year 2020 below 15 [106 m3/yr]. An annual aquifer depletion that is realistic and acceptable and that qualifies as sustainable utilization ought be established. An acceptable annual groundwater extraction should sustain a prosperous local economy, while water conservation measures, education, and regulations ought to promote water-efficient irrigation methods, eliminate losses in the water distribution system, and discourages wasteful water use. Circumstantial evidence uncovered after completion of the water budget analysis suggested that the annual irrigation water used in the water budget analysis was a low estimate while groundwater recharge from rainfall was a high estimate. Thus, projected annual groundwater deficits are potentially larger than reported in this study.