Use of solute and isotopic composition of ground water to constrain the ground water flow system of the Azraq area, Jordan

This study shows that hydrological systems in arid areas where water level data are incomplete can be better understood and constrained by using chemical and isotopic data. These constraints significantly alter the conceptual hydrological model of the Azraq area. Previous studies, based on water level data, suggest that water in the Azraq oasis is derived from two major piezometric highs; the western basalt aquifer to the northwest and the Tulul el Ashaquif highlands to the northeast of the oasis. Water from the Tulul el Ashaquif aquifer is also considered to drain to a piezometric low at Ruwaishid to the east, and then into deeper aquifers. Chemical data from this study show that the northwest basalt aquifer provides most of the water (80-85%) to the Azraq oasis. Water from the Tulul el Ashaquif supplies a relatively small proportion, but due to its high solute content, imparts its chemical signature on the oasis water. This study has shown that water from Tulul el Ashaquif are not supplied to the Ruwaishid area, as previously thought. Stable isotopic data show that each piezometric high contains water which originated in a distinct climatic setting. Both water types are poor in tritium. Traces of tritium at the Azraq oasis and at Ruwaishid indicate some recent local recharge.