4.3 Viewing Large Aquifer Systems at Different Spatial Scales

The information on large aquifers systems presented in this book takes a macroscopic perspective. This enables a view of the aquifer systems in a global context, to compare the different aquifer systems and their state based on simple indicators, and to get an idea of the magnitude of the opportunities and challenges they offer. While providing these interesting insights, information at this spatial scale has its limitations. It is of little direct use for practical activities such as planning for groundwater abstraction wells or defining and designing groundwater management interventions. Such activities need to be guided by more detailed information on a local, sub-regional or regional scale, paying ample attention to the spatial variations of aquifer properties, groundwater state variables and interactions with people and the environment. Assessment studies and monitoring activities in support of such practical activities usually cover areas of limited extent, much smaller than the size of large aquifers systems. Information acquired at different spatial scales is complementary, with the data from each scale serving different types of analysis or decisions, and together they cover the entire field from local to global.