Flow Discontinuities Between Adjacent Phreatic and Confined Aquifers Indicated by 14C and Other Parameters

Phreatic aquifers are often regarded as recharge zones feeding adjacent confined systems. A continuous through-flow is commonly envisaged, controlled by (and deduced from) water level gradients and transmissivities. However, in certain cases a discontinuity is observed between the phreatic and confined parts of a system, reflected in abrupt changes in the chemical

Fig. 11.15 Contours of electrical conductivity of groundwaters of the Watrack Shedi subbasin. The phreatic section reveals fresh water values around 1000 mmho/ cm, whereas gradual salinization is observed down-gradient in the confined section. (From Borole et al., 1979.)

and isotopic compositions and, especially, in tritium, 14C, 4He, and other age indicators. Six case studies that reveal phreatic-confined discontinuities are briefly discussed below. They were described in detail in Mazor and Kroitoru (1987).

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