GROUNDWATER USE AND ITS IMPLICATIONS IN AN AGRICULTURAL AREA: A CASE STUDY IN A FLUVIAL AQUIFER BY GROUNDWATER NUMERICAL MODELING

In Mexico, the main use of groundwater is agriculture, representing 70% of the country’s total withdrawals. Currently, with the increase of this activity and the poor efficiency of irrigation systems, there is a danger of affecting the availability of storage of aquifers. The Rioverde fluvial aquifer is characterized by highly permeable sediments. The main economic activity in this area is the highly profitable irrigated agriculture, supported by groundwater (75% of total extraction, approximately).

The objective of this research was to analyze and understanding the hydrogeological behavior of the fluvial aquifer and groundwater use in study region, by implementing groundwater extraction schemes in a numerical model, and its implications in the agricultural area in terms of water quantity. In this investigation, a conceptual model of the hydrodynamic functioning of the fluvial aquifer was developed by combining hydrogeological and geophysical methods, and implemented it in a numerical model of groundwater flow, which was calibrated and validated. The agricultural area obtains groundwater from an unconfined aquifer in unconsolidated sediments (100-300 m thickness), with hydraulic conductivity from 1.7-2.3 m/day and porosity 0.18-0.22. Groundwater flow determined from hydraulic head distribution is from the southwest area to the natural discharge zone in the northeast.

Subsequently, future scenarios were developed to predict the state of the study region in 2040: 1) Existing state (2019) and 2) Limited groundwater extraction according with concessions granted to users by the competent authorities. According to the results of the future scenario 1, pumping scheme will bring important changes in the hydraulic behavior of the aquifer being able to present drawdowns of almost 3 m/year; on scenario 2 minor variations occurs in the configuration of the water table with drawdowns of 1 m/year, approximately.