DESIGN OF GROUNDWATER MONITORING NETWORKS FOR THE SUSTAINABLE MANAGEMENT OF FLUVIAL AQUIFERS

Groundwater monitoring networks (GMN) are used to obtain information on quality, piezometry, geochemistry, among others; however, there are different methodologies to obtain this type of data which consider 1) those based on elements of hydrogeological conceptual models, 2) those that execute data analysis with statistical techniques, and 3) those that use groundwater flow numerical models, therefore the objective of this study was to establish a GMN in the fluvial aquifer of Calera, Mexico, in order to obtain the piezometry. The Calera region is a closed drainage basin located in a regional graben structure developed during the Tertiary, where a thick sequence of fluvial materials was deposited. The hydrogeologic basement include Mesozoic and Lower Tertiary formations (schists, sedimentary rocks, basalts, shales, sandstone, calcareous schist with greywackes, conglomerates). Groundwater flow in volcanoclastic rocks (Late Oligocene) and basin fill sediments (Tertiary). Piezometric data indicate groundwater flow from the south and southwest region to the main discharge area in the north of the basin. Long-term intensive groundwater extraction has produced the decline of water levels at the rate of 1.2-1.8 m/yr. For this purpose, a method was implemented that allowed consider the existing GMN, in addition to priority zones (PZ), in which a greater weight was given to the wells located within, all based on the historical information available to determine the sampling order priority for each of the wells analyzed. The results of the study showed 4 possible scenarios: first scenario (optimal) showed a rapid decrease in variance; second scenario considered the existing GMN as the first sampling sites, reflecting a decrease lower than the optimal scenario; third scenario considered not only the established in the second scenario, but also the PZ showing a lower decrease than the latter scenario; fourth scenario showed the slowest decrease in variance neither considering the previous GMN nor the PZ. Thus, considering the objective of the project, the third scenario fulfilled the criteria established in the study. Finally, the scenarios analyzed showed different behaviors of decrease in variance and allowed remark the differences between each scenario evaluated.