Hydrogeological assessment of a managed aquifer recharge site at the Wala reservoir, Jordan
2 Ministry of Energy and Mineral Resources, Jordan
P 2.2 in Aquifer systems in Europe and beyond
Jordan is facing a major challenge in terms of a continuous water supply of its rapidly growing population along with a sustainable use of its surface and groundwater resources. The increasing water demand has led to falling groundwater levels in most of the regional aquifers and to a deterioration of their water quality. This situation is exacerbated by the prevailing semi-arid climate, which led to a strong variability in water availability, observable in short but strong rainfall events in the winter and long-lasting aridity during summer. The largest proportion of rainfall evaporates and or leads to occasional surface runoff generation and only a small fraction contributes to natural groundwater recharge by infiltration. For the utilization of the unused surface runoff, numerous dams were built in the past decades in the side wadis of the Jordan Valley, among which the Wala reservoir is the only managed aquifer recharge (MAR) site. Since 2002, the Wala reservoir stored flood water in the winter seasons and recharged it to the karst aquifer below. This helped rising the groundwater levels and supplied water to the Hidan wellfield 7 km further downstream. However, due to aquifer heterogeneity and the karst typical flow behavior of fast flow and slow depletion, the hydraulic behavior is mostly unknown and therefore aggravates the reservoir and wellfield management. This study presents the evaluation and assessment of the reservoir sedimentation processes and its impact on the water balance, as well as the impact of surface infiltration on the chemical and isotopic composition of the groundwater from 2002 to 2012. Since the reservoir was constructed, around 85.0 million cubic meters (MCM) water were stored, whereof around 74.1 MCM infiltrated and 7.8 MCM evaporated until 2012. Sedimentation in the reservoir was investigated and showed a reduction of the storage capacity by about 1.6 MCM by silt and clay, which caused also a decrease in infiltration (Xanke et al., 2015). The impact of the surface water infiltration on groundwater was detected by using Tritium data and the mean residence times of groundwater, calculated with the 14C-method. These results were used to develop a hydrogeological conceptual groundwater flow model which contributes to a better understanding of the prevailing hydraulic conditions. This can serve as a basis for further studies of the Wala reservoir and the Hidan wellfield.
XANKE, J., GOEPPERT, N., SAWARIEH, A., LIESCH, T., Kinger, J., Ali, W., Hötzl, H., Hadidi, K., Goldscheider, N. (2015), Impact of managed aquifer recharge on the chemical and isotopic composition of a karst aquifer, Wala reservoir, Jordan. In: Hydrogeol Journal, S. 1-14. DOI: 10.1007/s10040-015-1233-6.