Regional aquifers are large continuous systems that produce enough water for entire regions to use. As indicated by Toth's conceptual diagram, regional aquifers tend to be deeper and therefore less connected with surface water. This is not always the case, particularly with respect to extensive fluvial systems associated with active rivers and in carbonate systems that are near the surface and have been subject to extensive dissolution (karst).
Borrowing from the USGS Aquifer Basics page, we can divide regional aquifers into six categories based upon geology.
Click on one of these rock types to view some information about them:
