Water Supply Source Evaluation in Unmanaged Aquifer Recharge Zones: The Mezquital Valley (Mexico) Case Study

Abstract

Abstract:The Mezquital Valley (MV) hosts the largest unmanaged aquifer recharge scheme in the world. The metropolitan area of Mexico City discharges~60 m 3 /s of raw wastewater into the valley, a substantial share of which infiltrates into the regional aquifer. In this work, we aim to develop a comprehensive approach, adapted from oil and gas reservoir modeling frameworks, to assess water supply sources located downgradient from unmanaged aquifer recharge zones. The methodology is demonstrated through its application to the Mezquital Valley region. Geological, geoelectrical, petrophysical and hydraulic information is combined into a 3D subsurface model and used to evaluate downgradient supply sources. Although hydrogeochemical variables are yet to be assessed, outcomes suggest that the newly-found groundwater sources may provide a long-term solution for water supply. Piezometric analyses based on 25-year records suggest that the MV is close to steady-state conditions. Thus, unmanaged recharge seems to have been regulating the groundwater balance for the last decades. The transition from unmanaged to managed recharge is expected to provide benefits to the MV inhabitants. It will also be likely to generate new uncertainties in relation to aquifer dynamics and downgradient systems.

Atoyac River Pollution in the Metropolitan Area of Puebla, México

“…The Mezquital Valley aquifer is the most emblematic case because the metropolitan area of Mexico City discharges~60 m 3 /s of non-processed wastewater in the valley and the aquifer recharge is made with part of the wastewater that leads to irrigation channels, which explains the presence of FC and chemical contaminants in the water of the wells of the region [56,[67][68][69]. This situation can be presented in EPG, since all wells evaluated showed a high presence of mesophilic aerobic bacteria (1 × 10 5 CFU/100 mL ± 1.14 × 10 5 ) and fecal contamination, to a lesser or greater degree, with the presence of important species [58,59,70] such as E. coli, Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, Klebsiella oxytoca and Klebsiella pneumoniae, which represents a threat to the population, considering that the water used for human consumption and personal hygiene must be free of pathogenic microorganisms [59]. These bacteria, isolated in wells, produce infections in the central nervous system, the digestive system (Escherichia), the lower respiratory tract, the bloodstream, and the urinary tract (Klebsiella, Enterobacter and Escherichia), and wells are not chlorinated in 88% of houses.…”

Karst Conduit Networks, Connectivity and Recharge Dynamics of a Sinkhole

“…where ρ (Ω.m) is the bulk resistivity of saturated rock, ρ w (Ω.m) is the resistivity of pore water, α is the tortuosity factor and m is the cementation coefficient (Shah & Sinh, 2005, Hernandez-Espriu, 2017. Values for carbonate media, α=1 and m=2 (Hernandez-Espriu, 2017) were taken for the study aquifer.…”

Making the Water–Soil–Waste Nexus Work: Framing the Boundaries of Resource Flows

“…About 60 m 3 /s is discharged into the Mezquital Valley by the network of channels and tunnels [59]. The Mezquital Valley is the largest agricultural area irrigated with untreated wastewater in the world, with an area of 90,000 ha [60].…”

“…Three agricultural districts (Tula, Alfajayucan and Ajacuba) are directly benefitting from this wastewater irrigation scheme [63]. In terms of water balance, Hernandez-Espriu et al [59] further pointed out that the transition from unmanaged to managed aquifer recharge is expected to provide multiple benefits to the inhabitants of the valley.…”