Groundwater Flow Systems and Their Response to Climate Change: A Need for a Water-System View Approach

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Problem statement: The interest in early hydrogeological studies was t he aquifer unit, as it is the physical media that stores and permits groun dwater transfers from the recharge zone to the discharge zone, making groundwater available to bor eholes for water extraction. Approach: Recently, the aquifer concept has been complemented by the groundwater flow system theory, where groundwater may be defined by local, intermediate a nd regional flow systems. This implies that groundwater may travel from one aquifer unit to ano ther aquifer unit (or more) located above or below the former. Water in a local flow system takes mont hs or several years to travel from the recharge to the discharge zone. These flows usually transfer th e best natural quality water, so a reduction in precipitation would lessen recharge and diminish st ored water, making them more vulnerable to contamination and variability in climatic condition s. Thus, there is a need to define local flows and to enhance actions to protect them from contamination and inefficient extraction. Results: In contrast to local flows, intermediate and regional flows travel from a region, or country, into another, with thei r recharge processes usually taking place in a zone l ocated far away from the discharge zone (natural or by boreholes). There is a need of groundwater flow sys tems evaluation by means of an integrated wide system-view analysis of partial evidence represente d by surface (soil and vegetation covers) as well a s hydraulic, isotopic and chemical groundwater charac terization in the related geological media where th e depth of actual basement rock is paramount as well as discharge areas. The flow system definition may assist in extraction management strategies to contr ol related issues as subsidence, obtained the water quality change, desiccation of springs and water bo dies, soil erosion, flooding response, contaminatio n processes in recharge areas, among others; many of which could be efficiently managed leaning on groundwater functioning. There is increasing eviden ce that climate becoming more variable and key driver of ecosystem health. Even with climate stabi lity, most developing countries will confront serio us water problems by the mid-21st century due to an in sufficient knowledge of the functioning of their groundwater sources representing ≈ 99% of available water. Conclusion: Many such problems may be adequately controlled when local flows are defined, since changes in climatic condition are more prone to affect local flows rather than intermediate and reg ional flows. The value of the flow systems arises f rom the fact that a wide system view analysis allows ad equate crossed examination among relevant data from where water management proposals might more adequately represent field conditions. Examples of successful application of the groundwater flow syst ems in Mexico and Argentina will be presented including: induced fluoride control, subsidence res ponse, desiccation of springs, flooding water origi n definition, basement position in flow-system contro l, inter-basin flow.