Zoning of protective capacity and vulnerability to contamination of Texcoco aquifer, State of Mexico

Abstract

This study estimated the protective capacity and natural intrinsic vulnerability of the Texcoco aquifer combining the Aquifer Vulnerability Index method (AVI) and the Dar Zarrouk geoelectric parameter (unitary longitudinal conductance, S). Lacustrine deposits, alluvial materials, and stratified volcanic deposits form the Texcoco aquifer. It is located in the east of the Valley of Mexico. Eighty-seven (87) Schlumberger vertical electric sounding (VES) were made and distributed in different profiles in the aquifer area. The VES data were collected in the field with a Terrameter SAS-300B resistivity meter with 750 m current electrode opening on both sides of a common center and interpreted with the Interpex IX1D software. The longitudinal conductance was obtained from the process of inversion of the data, and maps were elaborated with the kriging method and minimum curvature in Surfer V16. The thickness of the upper layer of the unsaturated zone varies between 0.3 and 10.5 m. The longitudinal conductance of the upper layer presents values from 0.0 to 75 Siemens/m. The groundwater level in the aquifer has an elevation of 2140 m asl in the south-central zone of the study area to 2290 m asl in the foothills of the Sierra de Río Frío. The AVI method allows us to correlate the hydraulic conductivity Kv (m/d) data and the thickness h (m) of the unsaturated zone to determine values of the hydraulic resistance C = 1.4 to 3.9 days. The obtained results are of interest to the municipal authorities in planning and deciding to preserve the underground water resource.