Stable isotope survey of the fresh water occurrences in Israel and the Northern Jordan Rift Valley

The stable isotope composition (Oxygen-18 and Deuterium) of the meteoric water cycle in Israel is presented. The survey comprises space and time variations of isotopic abundance in precipitation, surface and groundwater sources. Both the effect of the geomorphology on cloud evolution and of secondary evaporation from falling droplets under the cloud, determine the isotope composition of precipitation. In the mountainous aquifers the isotope composition, more or less, matches that of precipitation on the recharge areas. In the coastal plain and the inland valleys, on the other hand, we note further enrichment of heavy isotopic species in groundwaters relative to local precipitation. It is shown that the degree of aridity in different regions in the country is reflected in the isotopic composition, particularly in the value of parameter d = δ_D - 8δl8_O. The surface water survey includes that of the Upper Jordan river system. The isotope data are used to assess the hydrographical structure of the combined Jordan flow and the role that water loss by evaporation plays in the system's water balance. The isotope composition of the surface waters of the Dead Sea are also given.