Lens (hydrology)

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In hydrology, a lens, also called freshwater lens or Ghyben-Herzberg lens, is a convex layer of fresh groundwater that floats above the denser saltwater and is usually found on small coral or limestone islands and atolls. This aquifer of fresh water is recharged through precipitation that infiltrates the top layer of soil and percolates downward until it reaches the saturated zone. The recharge rate of the lens can be summarized by the following equation: R = p − E T {\displaystyle R=p-ET} Where R {\displaystyle R} is the recharge rate in meters, p {\displaystyle p} is precipitation (m), and E T {\displaystyle ET} is evapotranspiration (m) of water. With higher amounts of recharge, the hydraulic head is increased, and a thick freshwater lens is maintained through...

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