SEMIDE Système Euro-Méditerranéen d'Information sur les savoir-faire dans le Domaine de l'Eau

Malta Focal Point
 Last update: September, 2007

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The Ghyben-Herzberg Model

The Mean Sea Level Aquifers of the Maltese Islands have formed basically due to the differences in density of sea water and fresh water. This principal was discovered by two scientist Baden-Ghyben and Herzberg.

 

Fresh water (r f) is lighter than sea water (r s).

Freshwater has a density of 1.0g/cm3 whilst salt water is slightly denser: 1.025g/cm3. Because of this fresh water floats on top of the sea water. Rainwater that percolates the ground depresses the salty water found beneath and thus gives rise to a lens shaped profile. The transition zone between the salty sea water and fresh groundwater is not a distinct boundary but a zone of brackish water since the salty sea water and fresh water intermix. Such a zone on the Maltese islands is greatly influenced by seasonal fluctuations in rainfall. Yet the amount of water abstracted for human use also greatly influences this zone. Boreholes that penetrate deeply within this transition zone results in sea water intrusion.

 

 

 

 

 

The Baden Ghyben-Herzberg relationship states that for every foot (h) of groundwater above sea level there are forty feet of fresh water below sea level (H)

Thus:

 

adapted from McLane, C; Magelky, R; and Sieling, D. (2002)


 

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