Quantifying water exchanged between surface and groundwater of the Independent aquifer in central Mexico

In the Guanajuato State, the rapidly growing population, industry, and commercial agriculture depend heavily on water resources, and especially on groundwater. Our work is based on the data measured by our group and data collected from federal (CNA) and state water (CEA) commissions and previous research of our collaborators in the Independent Basin (IB) and the subsurface Independent Aquifer (IA), which are located in the central of State of Guanajuato, Mexico. The data were analyzed for a temporal-spatial distribution, and the results suggest that the IA has significantly been overexploited since 2010, which greatly reduced the flows in rivers and streams. The average depth to water table in IA was 109 m in 2015, and the average historic drawdown rate in wells was 1 m/yr from 2010 to 2015. Fifty years ago, rivers had a significant flow year-round in the Independent Basin. These rivers provided the main source of irrigation water for agricultural land near the river courses. The strong connection between the river beds and the aquifer and the rapid drawdown of groundwater, resulted in the rivers being transformed into ephemeral streams, and the volume of water in the Ignacio Allende reservoir at the bottom of the Basin's watershed to decline rapidly. Simultaneously, lack of surface water reduces the vertical recharge to the aquifer, resulting in a faster drop in the water table. The outcome of our work is a numerical forecast model using CORE code to model the effect of surface water to groundwater for different climate change and water resource management scenarios.

Keywords: Water resource management, Induced disequilibrium, Overexploitation, Recharge to the aquifer