A multi-environmental tracer study to determine groundwater residence times and recharge in a structurally complex multi-aquifer system

Abstract

Abstract. Despite being the main drinking water resource for over 5 million people, the water balance of the Eastern Mountain Aquifer system on the western side of the Dead Sea is poorly understood. The regional aquifer consists of fractured and karstified limestone – aquifers of Cretaceous age, and it can be separated into a Cenomanian aquifer (upper aquifer) and Albian aquifer (lower aquifer). Both aquifers are exposed along the mountain ridge around Jerusalem, which is the main recharge area. From here, the recharged groundwater flows in a highly karstified aquifer system towards the east and discharges in springs in the lower Jordan Valley and Dead Sea region. We investigated the Eastern Mountain Aquifer system for groundwater flow, groundwater age and potential mixtures, and groundwater recharge. We combined 36Cl ∕ Cl, tritium, and the anthropogenic gases SF6, CFC-12 (chlorofluorocarbon) and CFC-11, while using CFC-113 as “dating” tracers to estimate the young water components inside the Eastern Mountain Aquifer system. By application of lumped parameter models, we verified young groundwater components from the last 10 to 30 years and an admixture of a groundwater component older than about 70 years. Concentrations of nitrate, simazine (pesticide), acesulfame K (ACE-K; artificial sweetener) and naproxen (NAP; drug) in the groundwater were further indications of infiltration during the last 30 years. The combination of multiple environmental tracers and lumped parameter modelling helped to understand the groundwater age distribution and to estimate recharge despite scarce data in this very complex hydrogeological setting. Our groundwater recharge rates support groundwater management of this politically difficult area and can be used to inform and calibrate ongoing groundwater flow models.

Geochemical and isotopic tracers to define the aquifer’s vulnerability: the case study of the alluvial multi-aquifer system of the Friulian plain

“…Both the intermediate and the deep aquifer waters (FVAs and FVAd) and wastewaters (FVF) are identified as sub-modern waters with low values of 3 H ranging between 3 and 4.5 TU, which is lower than the isotopic footprint of the meteoric precipitation, suggesting a longer residence time in the subsoil with an estimated age between 10 and 50 years. Generally, in complex multi-aquifer systems, the progressive decrease of 3 H in the waters from the recharge areas to the depth is linked to the nature of the aquifers with regional water circulation (Cao et al, 2020 ; Wilske et al, 2020 ).…”

Estimation of Groundwater Residence Time Using Radiocarbon and Stable Isotope Ratio in Dissolved Inorganic Carbon and Soil CO2

“…In the DM, these processes along the transport path and aquifer are taken into account by the dispersion parameter which is given by the inverse of Peclet number (Zuber and Maloszewski 2000). Peclet number for recharge patterns, topography and aquifer set up for the present case would vary in the range of 10-20 as discussed in Wilske et al (2020) giving a dispersion parameter in the range of 0.05-0.1. For this range of dispersion parameters, the variation in the residence times of groundwater with radiocarbon ages are shown in Figure 8.…”

Chiral Separation of Metolachlor Metabolites in a Single, Large Volume Injection to Facilitate Watershed Tracer Studies

“…Finally, we have added the analysis of MOXA, which was not included in the previous watershed studies. Capitalizing on the use of multiple tracers will allow us to illuminate the uncertainties in watershed age distributions in hydrologically complex systems. − …”