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Abstract

The endorheic basin of Mexico is geologically made up of a set of grabens that gave rise to a system of 5 lakes, mainly recharged by a hydrographic system made up of 47 rivers, in addition to the discharges from springs and the bottom of the lakes, by direct connection with the aquifer. Historically, intermittent and perennial springs have been reported; the last ones were, for many centuries, one of the main sources of freshwater supply in the basin since the lake's water was brackish, a situation that was later used by an important salt extraction industry. This study compiled 847 pairs of isotopic data of the water molecule (δ18O, δ2H) from different origins (meteoric, surface, and groundwater). The observed variations from 1974 to 2020 reflect the processes and interactions between the superficial and subterranean hydrological systems by identifying behavior patterns through a historical and regional approach. In a 2021 sampling, 38 isotopic data were added, verifying that they reproduce historical patterns in the recharge areas, plain, and areas of low groundwater quality (East of the basin). The isotopic results have been integrated into a recent geological description to strengthen the reformulation of the conceptual model of the Basin of Mexico. All this considers the recent changes generated in the hydrological systems due to intensive extraction associated with increased water demand.