| dc.description.abstracteng | Understanding the karst aquifer response to precipitation and contaminants transport, especially in arid to semi-arid areas, is a very important issue and a challenge due to the unique and heterogeneous characteristics of karst aquifers. Monitoring the water travel time through karst aquifers and the response to precipitation events can provide good information about the characteristics of water and pollutant flow through the aquifer. This can subsequently help provide proper protection for the aquifer against pollution to sustain the water resources for the coming generations.
Within this study, different methods and approaches were developed and applied in order to characterise the karst aquifer system of the Tanour and Rasoun springs and the flow dynamics within the aquifer and to develop a process-oriented method for vulnerability assessment based on the monitoring of different multi-spatially variable parameters of travel time. The karst aquifer of the Tanour and Rasoun springs (about 75 km2 northwest of the capital city of Amman) catchment area (~ 36 km2) was chosen as a case study due to the pollution events that occur at both of the springs, the high importance of these karst springs as the primary local drinking water supply for the surrounding villages and to fill a gap in the literature regarding the characteristics of the karst aquifer in this area.
To better understand the vulnerability of the karst aquifer of the Tanour and Rasoun springs to pollution events and the capability of the aquifer for the natural attenuation of pollutants based on the natural characteristics of the aquifer itself, COP and EPIK intrinsic vulnerability assessment methods were applied. Based on the applied COP method, spatial distribution of groundwater vulnerability is as follows: (1) high (37%), (2) moderate (34.8%), (3) low (20.1%), and (4) very low (8.1%). While in the EPIK vulnerability assessment method, only two out of four vulnerability classes characterise the catchment area: very highly vulnerable areas (38.4%) and moderately vulnerable areas (61.6%).
The understanding of the groundwater pathways and movement within the epikarst is fundamental to evaluate pollution risks from point and non-point sources in karst aquifer systems. A travel time physics based method was developed and applied by integrating flow path lengths with the sub-surface groundwater transport velocity through the epikarst zone, towards the streams as a final recharge point. The base flow recession curve method was used in order to estimate the transmissivity values of the epikarst zone as 3.58 * 102 m2/d. Final water travel times were applied within three different scenarios of the hydraulic conductivity values of the epikarst zone, which was calculated based on three different assumed thicknesses of the epikarst zone. The applied method showed that around 97% of the catchment area exhibits a water travel time of up to 5 days.
The analysed stable isotopes of oxygen and hydrogen in both of the Tanour and Rasoun springs water, in combination with other different automated monitored parameters, including turbidity, water temperature and electrical conductivity, in addition to the Tanour spring discharge, showed that the springs response to precipitation events is very rapid. Both springs responded to the rainfall events with an maximum water travel time of two to four days, except during the two intensive snowfall events that occurred in the winter season 2014/2015, where the maximum water travel time was nine to eleven day for the first snowfall event and three to five days for the second snowfall event. The difference in water travel times between the two snow events is related to other different factors that affected the snow melting process. The LMWL for the catchment area was defined as δ2H = 7.66 * δ18O + 24.43‰ (R2 = 0.98).
Pollution events in karst aquifers is a big problem due to the limited natural attenuation of pollutants resulting from fast water travel times and the thin, or absent, protective cover. At Tanour spring, both of the TOC and oxygen saturation showed a high sensitivity to pollution events from the olive mills wastewater. Clear, strong and wide-ranging potassium concentration peaks were recorded in Tanour and Rasoun springs during the pollution and recharge events. The measured potassium concentrations were used in order to develop a method for the quantification of the leaked wastewater towards Tanour spring (from the olive mills wastewater) and Rasoun spring (from domestic wastewater), based on the springs discharge volumes and the measured potassium concentration in the springs water and in the undiluted wastewater. | de |