A quantitative transport-time-based vulnerability assessment approach for non-point-source pollution using a spatially distributed geographic information system (GIS)-generated topographic model was developed for the karst aquifer system feeding the Tanour and Rasoun springs in NW Jordan. The approach implies the assessment of the groundwater residence times in different compartments of the karst system, i.e. the epikarst, the vadose zone and the phreatic system. Groundwater transport times within the epikarst zone were determined by employing two main variables: (1) the length of the flow path, and (2) the transport velocity between the assumed point of subsurface infiltration into the soil and the location for the actual groundwater recharge at the ephemeral streams. Sub-horizontal lateral flow is assumed for the epikarst. The base-flow recession curve method was employed to estimate the effective, average and catchment-wide transmissivity of the epikarst. Based on the calculated transmissivity, three different hydraulic conductivity values were assumed to assess the effect of the unknown average saturated thickness of the epikarst. The developed method was validated by independent measurements of the transport-time-based on the δ¹⁸O breakthrough signal in the spring catchment discharge, following a recharge event. The transport-time distribution map, calculated based on flow-path length towards the streams and average solute transport velocity, shows high correlation with the catchment-averaged stable isotopes’ breakthrough curves. Because of the intensive karstification below the stream bed, residence times in the vadose and the phreatic zones can be assumed to be negligible compared to the transport times in the epikarst.

针对为约旦西北部的Tanour和Rasoun泉提供岩溶含水层系统开发了一种定量的，基于运输时间的非点源污染脆弱性评估方法，该方法使用空间分布的地理信息系统（GIS）生成的地形模型。该方法意味着评估岩溶系统不同隔室（即表岩溶，渗流带和潜水系统）中地下水的停留时间。表层岩溶带内的地下水运移时间是通过两个主要变量确定的：（1）流动路径的长度，（2）假定地下渗入土壤的点与实际地下水补给位置之间的运移速度在短暂的溪流中。上岩溶假定为亚水平横向流。采用基流衰退曲线法估算表岩溶的有效，平均和集水区的透射率。基于计算出的透射率，假定使用三个不同的水力传导率值来评估表岩溶的未知平均饱和厚度的影响。通过基于δ的运输时间的独立测量来验证所开发的方法补给事件发生后，弹簧集水器排放中的¹⁸ O突破信号。根据流向河流的流路长度和平均溶质传输速度计算出的传输时间分布图与流域平均稳定同位素的突破曲线高度相关。由于河床下方的强烈岩溶作用，与上岩溶岩的运移时间相比，在渗流区和潜水区的停留时间可以忽略不计。