A preliminary investigation of wadi–aquifer interaction in the semi-arid watershed of Faria, Palestine using tracer-based methodology

This paper aims to investigate the potential existence of wadi–aquifer interaction in the 320 km² semi-arid Faria catchment using a tracer-based methodology. Faria catchment is located in the northeastern part of the West Bank and accounts for 6 % of the total West Bank’s area. Surface runoff in the catchment consists mainly from springs discharge, runoff generated from winter storms, untreated wastewater effluent from the eastern part of Nablus City and Al-Faria refugee camp, and the return flow from the adjacent agricultural areas. As such, wadi–aquifer interaction may pose serious pressures on groundwater quality which is the only water source for the agricultural and domestic uses in the area. In this study, and in order to investigate the potential existence of wadi–aquifer interaction in the Faria catchment, a tracer-based experiment was conducted. The experiment was carried out using Uranine as a conservative tracer material. A representative reach of 600 m was chosen and was divided into four equal distances. A concentration curve was plotted at each section (monitoring point) with the help of OTIS (solute transport model for streams and rivers) which was used to calibrate the measured concentration curves. Accordingly, the flow rates were estimated at the different monitoring points. The obtained results proved that transmission losses took place in the wadi bed sediments of the selected reach and with different ratios. The percent loss in the flow rates’ values in the different sections ranged from 4.8 to 68.3 %. It was found that the largest transmission losses took place in the section between the first and the second monitoring points. In conclusion, tracer-based methodology is considered as a modern and innovative technique that was used via this research to understand the nature of the wadi–aquifer interaction in Faria catchment and to quantify it as well.