Schematic aquifer xsection usgs cir1186

A diagram showing the relation between confined and unconfined aquifers; figure 5 from USGS circular 1186; https://pubs.usgs.gov/circ/circ1186/html/gen_facts.html.
The regions in the figure correspond to:

light blue zones are aquifers,
darker blue hatched zone is an aquitard,
light brown (tan) section is the vadose zone (unsaturated zone), and
dark brown area is "impermeable" bedrock (an aquiclude).