Geologic structure and groundwater flow in the Pachuca–Zumpango sub-basin, central Mexico

Abstract.

This paper is a hydrogeologic characterisation of the Pachuca–Zumpango sub-basin in Central Mexico, mainly concerned with the shallow geologic structure of the region and its implications in groundwater flow. The structure is interpreted as a series of graben structures limited by normal faults of metrical surface displacement. The graben are filled by a sequence of approximately 2,000 m alluvial and pyroclastic material and lava flows. An upper-aquifer that consists of Quaternary–Tertiary lava flows and clastic material is intensively used to obtain water for municipal supply. Abstraction was carried out with no control or management policy and resulted in severe environmental impacts. Numerical modelling simulation scenarios with continuous increments in the abstraction rate of 0.660 m³/s in 5-year periods between 2000 and 2020 predict an overall increase in depth to potentiometric surface of 15 m (0.80 m/year). Soil consolidation computation in terms of calculated drawdown values was not an objective in this study; however, lowering of the potentiometric surface will eventually control soil subsidence, as observed elsewhere in Mexico City.