Columbia subject headings:
Aquifers.
Arid regions.
Igneous rocks.
Metamorphic rocks.
Water-supply.
Harvard subject headings:
Aquifers.
Arid regions
Igneous rocks
Metamorphic rocks
Water-supply
Princeton subject headings:
Aquifers.
Arid regions.
Igneous rocks.
Metamorphic rocks.
Water-supply.