Identification of recharge processes and mixing patterns by using CFC's and isotopic multi-tracing (δ18O, δ2H) of groundwater in a stratified volcanoclastic aquifer of the semiarid Amazcala Basin in Central Mexico

Understanding groundwater flow is essential for quantifying recharge and identifying relevant processes in an aquifer. Hydrogeochemical models have proven to be successful in identifying origin and processes during water recharge. We integrated the hydrogeochemistry, environmental isotopes and CFC technique to develop a conceptual and a groundwater mixing model of the Amazcala aquifer in Central Mexico. Results demonstrate that groundwater recharge consists of local meteoric recharge and a regional geothermal input. The local resident groundwater component represents the primary source of groundwater contributing with an average of 56% (sigma = 0.07). The second crucial component of groundwater is the contribution of the local meteoric component contribution with averages to 23% (sigma = 0.05). The third component is the regional geothermal component, which on average contributes to 21% (sigma = 0.03). Regional geothermal influence has been reported in several aquifers in volcanic regions. This geothermal input influences volcanic aquifers located in the Trans-Mexican Volcanic Belt and should be considered in the water balance budget. Excessive groundwater extraction raises the vulnerability of the aquifer to natural and/or anthropogenic pollution, affecting the quality of water. Understanding the hydrogeological system offers a useful framework for developing and executing Managed Aquifer Recharge strategies (MAR).