Line‐Source Multi‐Tracer Test for Assessing High Groundwater Velocity

Abstract

Segmented line-source multi-tracer injection is suggested as an effective method for assessing groundwater velocities and flow directions in subsurfaces characterized by high water flux. Modifying the common techniques of injecting a tracer into a well became necessary after point-source natural and forced gradient tracer tests ended with no reliable information on the local groundwater flow. The tracer's line-source increases the likelihood of success of the test and could provide additional information regarding the lateral heterogeneity of the aquifer. In a field experiment conducted in the northwestern part on the Dead Sea coast, tracers were injected into an 8-m-long line injection system perpendicular to the assumed flow direction. The injection system was divided into four separate segments with four different tracers. An array of five boreholes located within a 10 × 10 m area downstream was used for monitoring the tracers' transport. Two dye tracers (uranine and Na naphthionate) were injected in a long pulse of several hours into two of the injection pipe segments. Two other tracers (Rhenium oxide and Gd-DTPA) were instantaneously injected into the other two segments. The tracers were detected 0.7 to 2.3 h after injection in four of the five observation wells, located 2.3 to 10 m away from the injection system. The groundwater velocity was determined to be ∼80 to 170 m/d, based on the recoveries of the tracers. The groundwater flow direction was derived based on the arrival of the tracers and was found to be quite consistent with the apparent direction of the hydraulic gradient.

Localisation and temporal variability of groundwater discharge into the Dead Sea using thermal satellite data

“…Emergence gradually starts to disappear from the north over the subsequent two series leaving only inflow locations at the bay centre. Magal et al (2010) report similar findings and describe the gradual drying out of northern springs at the Ein Feshkha Nature Reserve. In contrast, during the last series (2010-2011) the springs seem to reappear along the entire bay.…”

“…First, the lateral retreat of the DS shoreline amounts to several tens of meters per year in areas with minor sea bed inclination such as at Ein Feshkha. This process possibly causes a relocation of groundwater flow and hence of springs as observed by Magal et al (2010) and hinders an analysis over the entire investigation period of 2000-2011. Secondly, groundwater flow is intermittent, thus requiring to base the analysis on multiple SST data to assure reliable and most of all representative results (Becker 2006;Mallast et al 2013).…”

“…While only a fraction (terrestrial springs) of total groundwater discharge to the DS can actually be monitored by direct measurements, data of the main spring area (Ein Feshkha) suggest that the total groundwater discharge rate is decreasing (Galili 2012) accompanied by changes in the groundwater flow-system (Hadas 2011;Magal et al 2010). Extending the monitoring program along the entire DS coast (ca.…”

An application of fluorescent tracer to groundwater tracking

“…Sodium fluorescein (C 20 H 10 Na 2 O 5 ; uranine; Acid Yellow 73; CAS 518-47-8) is used frequently (Fig. 1); Magal et al [4,11] used it to trace groundwater.…”

“…Reilly et al [3] recognized that tracers are useful in understanding and quantifying transport processes. Magal et al [4] analyzed tracers as matter carried by water which gives information concerning its direction and/or velocity as well as potential contaminant transportation. They can also help determine hydraulic conductivity [5], porosity, dispersivity [6] and other hydrogeological parameters.…”