title: 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.
authors.affiliation: Department of Environmental Hydrology & Microbiology, Zuckerberg Institute for Water Research, Blaustein Institute for Desert Studies, Ben Gurion University of the Negev, Sede Boqer 84990, Israel. einatm@mni.gov.il
authors.forename: Einat
authors.initials: E
authors.lastname: Magal
authors.forename: Noam
authors.initials: N
authors.lastname: Weisbrod
authors.forename: Alexander
authors.initials: A
authors.lastname: Yakirevich
authors.forename: Daniel
authors.initials: D
authors.lastname: Kurtzman
authors.forename: Yoseph
authors.initials: Y
authors.lastname: Yechieli
mesh_terms: D003287:Contrast Media / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D007557:Israel; D008962:Models, Theoretical; D014872:Water Movements; D014881:Water Supply
chemical_list: D003287:Contrast Media