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Free keywords:
Recharge, Infiltration, Wadi Qilt, Jericho Plain, Major elements, Temporal change of composition, Spatial change of composition, Upper mountain sub-aquifer, Pollution, Karst aquifer
Abstract:
The spatial and temporal changes of the composition
of the groundwater from the springs along the Wadi
Qilt stream running from the Jerusalem–Ramallah Mountains
towards the Jericho Plain is studied during the
hydrological year 2006/2007. The residence time and the
intensity of recharge play an important role in controlling
the chemical composition of spring water which mainly
depends on distance from the main recharge area. A very
important factor is the oxidation of organics derived from
sewage and garbage resulting in variable dissolved CO2 and
associated HCO3 - concentration. High CO2 yields lower pH
values and thus under-saturation with respect to calcite and
dolomite. Low CO2 concentrations result in over-saturation.
Only at the beginning and at the end of the rainy season
calcite saturation is achieved. The degradation of dissolved
organic matter is a major source for increasing water hardness.
Besides dissolution of carbonates dissolved species
such as nitrate, chloride, and sulfate are leached from soil and
aquifer rocks together with only small amounts of Mg. Mg
not only originates from carbonates but also from Mg–Cl
waters are leached from aquifer rocks. Leaching of Mg–Cl
brines is particularly high at the beginning of the winter
season and lowest at its end. Two zones of recharge are
distinguishable. Zone 1 represented by Ein Fara and Ein Qilt
is fed directly through the infiltration of meteoric water and
surface runoff from the mountains along the eastern mountain
slopes with little groundwater residence time and high
flow rate. The second zone is near the western border of
Jericho at the foothills, which is mainly fed by the undergroundwater
flow from the eastern slopes with low surface
infiltration rate. This zone shows higher groundwater residence
time and slower flow rate than zone 1. Groundwater
residence time and the flow rate within the aquifer systems
are controlled by the geological structure of the aquifer, the
amount of active recharge to the aquifer, and the recharge
mechanism. The results of this study may be useful in
increasing the efficiency of freshwater exploitation in the
region. Some precautions, however, should be taken in future
plans of artificial recharge of the aquifers or surface-water
harvesting in the Wadi. Because of evaporation and associated
groundwater deterioration, the runoff water should be
artificially infiltrated in zones of Wadis with high storage
capacity of aquifers. Natural infiltration along the Wadis lead
to evaporation losses and less quality of groundwater.
