Evaluación hidrogeológica de la subcuenca de Tecocomulco, Estados de Hidalgo, Puebla y Tlaxcala, México

Resumen

The hydrogeologic framework of the Tecocomulco sub-basin corresponds to a NE-SW tectonic graben, widening at its northeastern portion. The graben infill is constituted by ~600 m of alluvial deposits and volcanoclastic sediments, 500 to 1,500 m volcanic rocks of different composition, and below, rhyolitic rocks and finally a calcareous local basement are found. In this paper each rock unit is considered a hydrogeological unit with hydraulic connection and forming an aquifer system. An aquitard exist toward the center of the plain that covers partially the intergranular part of the aquifer system, where it behaves as semiconfined one.

The regional geologic framework indicates that the subbasins of Tecocomulco, Apan and Sahagún have hydraulic communication through fractures in the consolidated units as well as through alluvial material that underlies the Quaternary volcanic relief. Considering the relative highest topographical position of the Tecocomulco sub-basin with respect to the other ones, it is concluded that it constitutes part of the recharge area of the others sub-basins. The configuration of pizometrics data determines a regional horizontal hydraulic gradient of 0.009⁰/₀₀, where the flow is from Tecocomulo towards Apan and Sahagún. The interpretation of the geochemical index Cl^- / HCO₃^- y (SO ₄^2- + HCO₃^-) / Cl^- confirms the direction of the groundwater flow as E-W.

The measurements of electric conductivity and temperature of the groundwater in two piezometers installed in the plain, show upward and downward vertical components of flow beetwen 5 and 50 m; while from 70 to 80 m depth the flow is upward and, deeper the flow is again downward. This suggests the existence of local, intermediate and regional groundwater flows.

The content of E. colli and Enterobacter in the groundwater vary from place to place, but in general it is above the permissible limits, suggesting that such water is related to very dynamic and relative shallow flow systems.

The groundwater budget show a small surplus of water, which is also part of the recharge toward the adjacent areas and it is one that makes possible the existence of the Tecocomulco Lake.