Chemical and isotopic methods for management of artificial recharge in Mazraha Station (Damascus Basin, Syria)

Artificially enhancing recharge rate into groundwater aquifer at specially designed facilities is an attractive option for increasing the storage capacity of potable water in arid and semi-arid region such as Damascus basin (Syria). Two dug wells (I and II) for water injection and 24 wells for water extraction are available in Mazraha station for artificial recharge experiment. Chemical and stable isotopes (d2H and d18O) were used to evaluate artificial recharge efficiency. 400 to 500*103?m3 of spring water were injected annually into the ambient shallow groundwater in Mazraha station, which is used later for drinking purpose. Ambient groundwater and injected spring water are calcium bicarbonate type with EC about 880 +/- 60 mu S/cm and 300 +/- 50 mu S/cm, respectively. The injected water is under saturated versus calcite and the ambient groundwater is over saturated, while the recovered water is near equilibrium. It was observed that the injection process formed a chemical dilution plume that improves the groundwater quality. Results demonstrate that the hydraulic conductivity of the aquifer is estimated around 6.8*10-4?m/s. The effective diameter of artificial recharge is limited to about 250?m from the injection wells. Mixing rate of 30% is required in order to reduce nitrate concentration below 50?mg/l which is considered the maximum concentration limit for potable water. Deuterium and oxygen-18 relationship demonstrates that mixing line between injected water and ambient groundwater has a slope of 6.1. Oxygen-18 and Cl- plot indicates that groundwater salinity origin is from mixing process, and no dissolution and evaporation were observed. These results demonstrate the efficiency of the artificial recharge experiments to restore groundwater storage capacity and to improve the water quality. Copyright (C) 2011 John Wiley & Sons, Ltd.