Submitted to: Proceedings of the World Environmental and Water Resources Congress Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/30/2012
Publication Date: 5/25/2012
Citation: Garbrecht, J.D., Mojarro, F., Echavarria, F., Bautista-Capetillo, C., Steiner, J.L. 2012. Water budget considerations regarding groundwater extraction targets in the Calera Aquifer watershed, Mexico. Proceedings of the World Environmental and Water Resources Congress Conference, May 20-25, 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, and to determine their effectiveness at reducing groundwater extraction. The scenario analysis showed that even with a 10% reduction in industrial and urban water use and a 50% reduction in irrigation water the annual groundwater deficit remains above 10 [106 m3/yr]. The political and socio-economic impacts of such large reductions in water use are likely to be unacceptable. At best, a freezing of industrial and urban water use at the level of year 2010 and a 50% reduction in irrigation water can be hoped for, which leads to an annual groundwater deficit of about 20 [106 m3/yr]. This is a great improvement over the 75 [106 m3/yr] groundwater deficit of year 2010, and could potentially be adopted as a target deficit that qualifies as sustainable utilization of groundwater resources. To achieve a 50% reduction in irrigation 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. However, circumstantial evidence suggested that the annual irrigation water reported in the literature and 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.