Age and recharge rate of groundwater reserves in Jordan
Jordan is one of the countries whose water scarcity is among the highest in the world. Sufficient precipitation is only found in the mountainous regions in the northwest of the country, where for this reason as well as the pleasant climate most of the residents live. On the contrary, almost 90% of the country is characterized by hot and dry desert climate. Jordan’s population experienced a high population growth during the past decades, especially by the inflow of refugees from the West Bank and nowadays from Iraq.
Since the seventies groundwater reserves have been used in order to supply the population with additional fresh water. This water often is very old, so called fossil groundwater. It percolated thousands of years ago, during the last ice age. That means that these groundwater reserves are being recharged very slowly. Thus, in major parts of the country groundwater tables decline, partially several meters a year. For a long-term water supply strategy, however, knowledge about groundwater recharge is essential.
In this project, several tracers such as 14C, 3H-3He, CFCs and SF6 are applied to determine residence times of groundwater in Jordan. The results obtained with these methods will provide quantitative information for an integrated assessment of the sustainability of the water management in this region. The results will be interpreted in the context of hydro(geo)logical groundwater flow models as well as together with results from the other projects, since this project is part of an interdisciplinary group working on different aspects of water and water policy in Jordan, including members of the faculties of biology, geography, law, physics and environmental economy (“Initiative for Excellence II: Global Change and Globalisation”).
A second question is the climate change in this region over the past several thousand years. From the noble gas content of the groundwater one can determine the mean annual temperature during the time of recharge, since the solubility of gases in water depends on temperature.
Another issue of this project is the investigation of thermal springs along the Jordan rift valley. Measured 3He/4He-ratio indicates if the water is of mantle or crustal origin. This information might help to explain the geology and the formation of the Jordan rift valley.
On a first field trip groundwater samples in the Azraq region, about 100km east of the capital Amman, have been collected. To get a first impression of the setting all sampled wells are located along the supposed groundwater flow path from the recharge area at Jebel al-Druze in Syria to the center of the Azraq basin.
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