Effects of Artificial Recharge via Injection Wells on Groundwater Quality in a Shallow Alluvial Aquifer, Central Damascus Basin

Kattan, Z.; Kadkoy, N.; Nasser, S.

Department of Geology, Atomic Energy Commission of Syria (AECS),  Damascus, P. O. Box 6091, Syrian Arab Republic.

Abstract

Environmental isotopes and hydrogeochemistry have been applied to study the effects of artificial recharge via injection wells on the groundwater quality of a shallow Quaternary alluvial aquifer in Damascus basin. The injectant water was taken from the surplus fresh water (TDS<250 mg/L) of Figeh spring during flood periods, and directly diverted to the injection well without any treatment. The total volume of injected water during the period (2006-2008) amounts 0.241557 million m3, whereas the total volume pumped form this site was »12.333 million m3. More than 145 water samples were taken from the injectant water and ambient groundwater of four wells drilled in the vicinity of the injection well. Nitrate (40<NO3-<57 mg/L), sulphate (180<SO42-<270 mg/L) and TDS (940<TDS<1155 mg/L) were the chemicals of concern, because of their high concentrations in the ambient groundwater, exceeding the established standards given for drinking water. After injection, nitrate concentration substantially decreased to values around 20-30 mg/L. while sulphate decreased to about 100 mg/L. Similarly, the TDS value dropped down to be close to that of the permitted maximum level of drinking water (500 mg/L). The significant difference in 18O concentration between the injectant water and ambient groundwater revealed that this natural tracer is useful and very sensitive, mostly for accurate estimate of mixing proportions. Rrelationships between the different parameter values and total injected water volume show slight increases in the case pf pH and O2. However, with the exception of bicarbonate, which shows the worse correlation (R2=-0.005), the remaining parameters show remarkably good correlations, especially chloride (R2=-0.995) and 18O (R2=-0.992). Although the climatic conditions prevailing in the area during the study period did not much help to inject further amounts of water, the finding were promising and encouraging to continuing this scheme of artificial recharge, as an alternative water management method, essentially in raising of the potential groundwater reserve and improving the water quality of this aquifer.