Well duh, it's an island. Maui's humid
tropical climate and diverse terrain set the stage for some
incredible hydrological features! Ground water, water which moves in
the porous space between rocks, is one of Maui's most important
resources because it is used for agriculture, drinking, and other
industrial needs.
The majority of rainfall returns to the
ocean via streams or the atmosphere by evaporation, but some remains
trapped in the earth. Beneath the surface, water stays in either the
saturated or unsaturated zone. In the unsaturated layer, water and
air are caught between the pore spaces in rocks; in contrast the
saturated layer contains only water and is refereed to as the water
table.
The amount of water Maui's volcanic
soil can hold, or its permeability, varies based primarily on the
viscosity of the the lava flow and topography. More compact flows
which occur as incline decreases generally hold less water resulting
in surface water.
Pipiwai Trail
Surface water occurs where the amount
of water flow exceeds the ground's ability to absorb it and generally
takes the form of streams and ponds. Components of surface water
include direct runoff, base flow (where streams meet the water
table), excess irrigation, and water returned from bank storage.
Streams in Maui can be effluent, meaning the water table facilitates
stream flow, or influent meaning they lose water to recharge the
aquifer.
Recharge, or the replacement of water
reserves in the ground, is particularly important because Maui
contains no desalination plants. Recharge occurs as precipitation,
runoff, and surface water makes its way to aquifers, the last
permeable layer of soil from which water can still be obtained.
Aquifers can be unconstrained like the water table, or constrained as
in trapped between two impermeable layers such as an artesian
aquifer.
