Dating of Groundwater Recharge in Two Small Adjacent Aquifers in Israel and Their Initial ¹⁴C Activities

Abstract

ABSTRACT. Radiocarbon and tritium determinations were carried out in 2 adjacent small aquifers in Israel. These aquifers have small storage capacities and good hydraulic properties. Darcy calculations suggest that the aquifers contain young waters, ~50 yr in age. 14 C concentrations in the Pleistocene aquifer are between 23-60 pMC, with the lowest activity related to contamination by petroleum-based fertilizers with no 14 C. 14 C concentrations in the Judea Group aquifer range from 62 to 95 pMC. An apparent difference of ~1000 yr is indicated for the average recharge age between the 2 aquifers. The tritium data suggests that the water in both aquifers is quite young. The 1000-yr difference is an artifact of initial isotopic fractionation differences through the unsaturated zone as established elsewhere for these 2 aquifers. When these individual fractionation factors (0.54 for the Pleistocene and 0.62 for the Judea Group) are used, it is revealed that both aquifers contain young water, in agreement with the Darcy calculation, which was recharged at the beginning of the period of thermonuclear atmospheric testing in the early 1960s.

The Yarkon-Taninim Aquifer (Judea Group Israel): What Radiocarbon Can Tell

“…K, the hydraulic conductivity is specific to each aquifer. For the upper sections of the Judea Group it is generally in the range of 100-200 m/day (Guttman et al 2011). This equation was employed for the whole aquifer (~140 km from the Beer Sheba region to the outlet of the Taninim springs) With a gradient of only (25-11 m)/140 km times the flow velocity should be small, and is calculated to be range of 3.7-7.3 m/yr.…”