Through Flow Systems Unconfined and Confined 281 Phreatic Unconfined Free Surface Aquifers

Phreatic aquifers have free communication with the aerated zone. The synonym free surface aquifer relates to the free communication between the aquifer and the vadose zone. An example is shown in Fig. 2.5. The term phreatic originates from the Greek word for a well.

Phreatic aquifers are the most exploited type of aquifer and most of the hydrochemist's work is performed on them. Phreatic aquifers are the collectors of infiltrating recharge water, and this process is well reflected in

Fig. 2.5 Basic components of a phreatic groundwater system: intake outcrops, an aerated zone, the water table, the saturated zone that constitutes a water-bearing aquifer, and impermeable rock beds of the aquiclude that seal the aquifer at its base.

the chemical, physical, and isotopic parameters of the aquifer's water. Water table fluctuations indicate the nature of recharge intake (sections 4.1 and 4.2), water table gradients indicate flow directions (section 4.3), water temperature indicates the nature of infiltration and depth of circulation (section 4.7), and tritium and radiocarbon concentrations reflect water ages and modes and velocity of flow (sections 10.7 and 11.8).

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