Moeck, C; Radny, D; Popp, A; Brennwald, M; Stoll, S; Auckenthaler, A; Berg, M; Schirmer, M: Characterization of a managed aquifer recharge system using multiple tracers, Science of the Total Environment, 609, 701-714 (2017), doi:10.1016/j.scitotenv.2017.07.211 [Link]
Knowledge about the residence timesof articially infiltrated water into an aquifer and the resulting flow paths is essential to developing groundwater-management schemes. To obtain this knowledge, a variety of tracers can be used to study residence times and gain information about subsurface processes. Although a variety of tracers exists, their interpretation can differ considerably due to subsurface heterogeneity, underlying assumptions, and sampling and analysis limitations. The current study systematically assesses information gained from seven different tracers during a pumping experiment at a site where drinking water is extracted from an aquifer close to contaminated areas and where groundwater is articially recharged by inltrating surface water. We demonstrate that the groundwater residence times estimated using dye and heat tracers are comparable when the thermal retardation for the heat tracer is considered. Furthermore, major ions, acesulfame, and stable isotopes (δ2H and δ18O) show that mixing of inltrated water and groundwater coming from the regional ow path occurred and a vertical stratication of the ow system exist. Based on the concentration patterns of dissolved gases (He, Ar, Kr, N2,andO2) and chlorinated solvents (e.g., tetrachloroethene), three temporal phases are observed in the ratio between inltrated water and regional groundwater during the pumping experiment. Variability in this ratio is signicantly related to changes in the pumping and inltration rates. During constant pumping rates, more inltrated water was extracted, which led to a higher dilution of the regional groundwater. An inltration interruption caused however, the ratio to change and more regional groundwater is extracted, which led to an increase in all concentrations. The obtained results are discussed for each tracer considered and its strengths and limitations are illustrated. Overall, it is demonstrated that aquifer heterogeneity and various subsurface processes necessitate application of multiple tracers to quantify uncertainty when identifying ow processes.

last modified 2018-06-22