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To overcome the limitations posed by the limited relevant data for recharge estimation in the Jordanian Yarmouk River basin, a mass balance methodology is developed which is simple and may be easily applied to other arid and semi-arid landscapes. This is done by integrating available climatic data with new rain-runoff relationship data, as measured using a specially designed and built artificial rainfall simulator, and changing soil moisture profiles through the hydrological year, as measured in the field. The amount of moisture in the soil after rainfall events changes as a result of both evaporation and of drainage into deeper levels (recharge). The soil moisture profiles at depth are evaluated using geophysical techniques that allow for the tracking of recharge fronts. After rainfall events, the distribution of its fate between runoff, evaporation and recharge is determined. Water in the soil beyond the field capacity can be demonstrated to mostly contribute to the ultimate groundwater recharge in the area. Water stored beyond the permanent wilting point is not considered to contribute significantly to the recharge regime. Because of the irregular nature of rainfall, the amount of recharge is found to be related to the spacing of wet and dry spells during the winter months more than the actual amount of rainfall. Prolonged dry periods allow for excess water to drain into the deeper soil and thus to the groundwater, and thus allow for more uptake following subsequent rainy events. Evaporation does not significantly contribute to the drying of the soils. Reanalysis of rainfall and evaporation data from previous years suggests that recharge rates range from 20 to 37 % of total rainfall amounts, as opposed to the currently assumed 5 %. [ABSTRACT FROM AUTHOR]

Abstract: Darwin''s “warm little pond”, where he envisioned life began, was perhaps metaphorical. However, it included the notion of separation, just as the Galápagos Islands are separated from mainland South America. We have studied a location where simple life flourishes far from other abundant life, i.e., a permanently damp surficial zone that is surrounded by stark desert in NE Jordan. NE Jordan is a young basaltic plateau with fresh outcrops. However, a positive-feedback process has produced local weathering at Biyar el Ghussein in the Tulul al Ashaqif area. Calcite, smectites, and goethite occur with parent minerals. Water that is inducing this weathering has come from rainfall, but the isotopic composition of abundant carbonate veins reveals a deep source, i.e., volcanogenic CO2. A local coincidence of groundwater and rising CO2 is inducing a positive-feedback process, enhancing a weakly perched water table through weathering of basalt. Additional perched water dissolves more volcanogenic CO2, accelerating decomposition of the basalt, and enlarging the aquiclude. [Copyright &y& Elsevier]

Chemical data are used to clarify the hydrogeological regime in the Mafraq area in northern Jordan, as well as to determine the status ofwater quality in the area. Groundwater from the shallow aquifer in the Mafraq area can be divided into two major groups according to geographical locations and chemical compositions. Water in the basaltic eastern part of the study area is characterized by the dominance of chloride, sulfate, sodium, and potassium, whereas waters in the limestone aquifers in the west are dominated by the same cations but have higher concentrations of bicarbonate. Stable isotopes show that the shallow aquifers contain a single water type which originated in a distinct climatic regime. This water type deviates from the Global Meteoric Water Line (MWL), as well as from the eastern Mediterranean meteoric water line. The waters are poor in tritium, and thus can be considered generally older than 50 years. Chemical mass balance models suggest that water is moving from the west towards the north of the study area. This suggests that waters from the different basins are separated from each other. Degradation of water quality can be attributed toagricultural fertilizers in most cases, although the waste-water treatment plant at Khirbet es Samra is a contributor to pollution in thesouthwestern part of the study area. [ABSTRACT FROM AUTHOR]