15. Evaluation of Groundwater Flow System Functioning in Mexico to Reduce Drought Impacts

Approximately 97 % of continental water on Earth is groundwater; the remainder includes surface water, water in the atmosphere, and water in living organisms. For Mexico to cope with drought conditions and minimize environmental impacts of human water usage, water source dynamics must be understood and utilized in the most efficient way. Groundwater moves from its recharge to its discharge area in flow systems, traveling through paths of different length and depth, resulting in flows that can be both local and regional. Regional flows are currently supplying about 95 % of the required water in arid regions, such as in Mexico’s San Luis Potosí Basin, which is the focal point of this study. The main objective is to highlight the importance of understanding groundwater flow systems to better identify the sources of recharge for any particular aquifer. Aquifer recharge can be derived from both local and regional sources and thus groundwater policy must consider the spatial and temporal dimensions of recharge in an attempt to efficiently manage extractions. Indeed, only through a better understanding of the biophysical relationship among groundwater components and drought can informed decisions be made.