Sweet Ground Water at Coasts
Date: September 12, 2002
The sea is full of water. Why is it that this water does
not percolate down to the aquifer and recharge it? Why the ground water
is sweet even in coastal areas?
Actually, seawater can enter an aquifer and recharge it. Ultimately it is
the balance of freshwater entering the land (as rain) versus the height of
sea level that determines which way the water flows. Water will flow from
the side with greater pressure, so if you draw down the groundwater table
sufficiently in a coastal zone (either by removal by excess water use, or
preventing freshwater recharge by paving the surface and channeling
rainfall directly to the sea), flow will come from the sea rather than
freshwater falling on the land. This has happened in some coastal areas as
a result of poorly planned development, which both increases water demands
on the aquifer (more people) and decreases recharge by rainfall (more area
paved over and rain runoff directed straight to the sea).
Donald Yee Ph.D.
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Update: June 2012