Residence times in subsurface hydrological systems, introduction to the Special Issue

Dreuzy, J.-R. de; Ginn, Timothy R.

doi:10.1016/j.jhydrol.2016.11.046

Cited by 11 publications

(8 citation statements)

References 124 publications

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“…where λ14 C is the 14 C decay constant (λ14 C = ln 2/5730), and a 14 C is the measured 14 C activity of the DIC in groundwater. Previous studies in the arid northwest of China (Edmunds et al, 2006;Huang et al, 2017) have concluded that a volumetric value of 20 % "dead" carbon derived from the aquifer matrix was recognised, which is consistent with the value (10 %-25 %) obtained by Vogel (1970). Therefore, the initial 14 C activity (a 0 14 C) of 80 pMC is used to correct groundwater 14 C ages (results are shown in Table 1), although this simple correction makes no attempt to correct the age of individual samples that may have experienced different waterrock interaction histories.…”

Section: The Apparent 14 C Agesmentioning

confidence: 93%

“…In the last glacial period, temperatures in the Xinjiang region (Li et al, 2015) and North China Plain (Chen et al, 2003) were cooler by approximately 10 and 6-9 • C, respectively, compared with the present day. Groundwater had a depleted δ 18 O value of −12.0 ‰ from the paleo-meteoric recharge in the arid northwest of China, such as in the Minqin basin (Edmunds et al, 2006), as well as in the east (Li et al, 2015) and west (Huang et al, 2017) Junggar Basin (Fig. 1a).…”

Section: Stable Isotope Indicationsmentioning

confidence: 99%

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Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Jin

Liang

et al. 2019

Hydrol. Earth Syst. Sci.

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Abstract. Investigating groundwater residence time and recharge sources is crucial for water resource management in the alluvium aquifers of arid basins. Environmental tracers (chlorofluorocarbons, 3H, 14C, δ2H, δ18O) and groundwater hydrochemical components are used for assessing groundwater mean residence times (MRTs) and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers in the Manas River basin (China). Aquifers under the Manas River upstream (south of the fault) contains very high 3H activity (41.1–60 TU), implying water recharge affected by the nuclear bomb tests of the 1960s. Carbon-14 groundwater age correlates positively with distance from mountain area (3000–5000 years in the midstream to > 7000 years in the downstream) and groundwater depth, but correlates negatively to a decrease in 3H activity (1.1 TU) and more negative δ18O values. This phenomenon reveals that the source of the deeper groundwater in the semi-confined aquifer is paleo-meteoric recharge. Special attention has been paid to the estimation of MRTs using CFCs and 3H by an exponential piston flow model. The results show that MRTs vary from 19 to 101 years by CFCs and from 19 to 158 years by 3H. MRTs estimated from 3H are much longer than those from CFCs, probably due to the different time lag of liquid (3H) and gas-phase CFCs through the unsaturated zone. The MRTs estimated by CFCs show good correlations with pH and the concentrations of SiO2 and SO42-, which can provide a possible approach to estimate first-order proxies of MRTs for groundwater age. The young water fractions are investigated by the CFC binary mixing method in the south and north of the fault. Relatively modern recharge is found in the south of the fault with young (post-1940) water fractions of 87 %–100 %, whereas in the north of the fault the young water fractions vary from 12 % to 91 %. This study shows that the combination of CFCs and 3H residence time tracers can help in analysing the groundwater MRTs and the recharge sources for the different mixing end-members.

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Section: The Apparent 14 C Agesmentioning

confidence: 93%

Section: Stable Isotope Indicationsmentioning

confidence: 99%

Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Jin

Liang

et al. 2019

Hydrol. Earth Syst. Sci.

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“…Changes in recharge could result in different age patterns (Goderniaux et al, 2013). Similarly, sea level changes that were disregarded in this study would have an effect on the groundwater age distribution in the coastal areas (Delsman et al, 2014). Prescribing a vertical coastal age boundary of zero years is another simplification that neglects the vertical mixing and dispersion, which would result in an increase of age with depth (Post et al, 2013).…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…Also, the uncertainties introduced by simplifying the density boundary effects are likely to be less impor-tant compared to other uncertainties associated, for example, with estimating the groundwater age by the procedures for correcting 14 C activities. A solution would, of course, be to use a fully density-driven model such as SEAWAT as in Meyer (2018) or Delsman et al (2014). But the very long computer runtimes for these kinds of models and the need for several thousand model runs during calibration made it infeasible to use a variable-density flow model.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Estimation of effective porosity in large-scale groundwater models by combining particle tracking, auto-calibration and <sup>14</sup>C dating

Meyer

Engesgaard

Hinsby

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Effective porosity plays an important role in contaminant management. However, the effective porosity is often assumed to be constant in space and hence heterogeneity is either neglected or simplified in transport model calibration. Based on a calibrated highly parametrized flow model, a three-dimensional advective transport model (MODPATH) of a 1300 km2 coastal area of southern Denmark and northern Germany is presented. A detailed voxel model represents the highly heterogeneous geological composition of the area. Inverse modelling of advective transport is used to estimate the effective porosity of 7 spatially distributed units based on apparent groundwater ages inferred from 11 14C measurements in Pleistocene and Miocene aquifers, corrected for the effects of diffusion and geochemical reactions. By calibration of the seven effective porosity units, the match between the observed and simulated ages is improved significantly, resulting in a reduction of ME of 99 % and RMS of 82 % compared to a uniform porosity approach. Groundwater ages range from a few hundred years in the Pleistocene to several thousand years in Miocene aquifers. The advective age distributions derived from particle tracking at each sampling well show unimodal (for younger ages) to multimodal (for older ages) shapes and thus reflect the heterogeneity that particles encounter along their travel path. The estimated effective porosity field, with values ranging between 4.3 % in clay and 45 % in sand formations, is used in a direct simulation of distributed mean groundwater ages. Although the absolute ages are affected by various uncertainties, a unique insight into the complex three-dimensional age distribution pattern and potential advance of young contaminated groundwater in the investigated regional aquifer system is provided, highlighting the importance of estimating effective porosity in groundwater transport modelling and the implications for groundwater quantity and quality assessment and management.

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“…In this study, it is demonstrated how the travel time distribution can be derived from a passive heat tracer experiment. There are a variety of other methods that can be used to determine travel times in subsurface systems, see, for example, the recent summary by de Dreuzy and Ginn ().…”

Section: Introductionmentioning

confidence: 99%

Estimating Travel Time in Bank Filtration Systems from a Numerical Model Based on DTS Measurements

Tombe¹,

Bakker

Schaars³

et al. 2017

Groundwater

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An approach is presented to determine the seasonal variations in travel time in a bank filtration system using a passive heat tracer test. The temperature in the aquifer varies seasonally because of temperature variations of the infiltrating surface water and at the soil surface. Temperature was measured with distributed temperature sensing along fiber optic cables that were inserted vertically into the aquifer with direct push equipment. The approach was applied to a bank filtration system consisting of a sequence of alternating, elongated recharge basins and rows of recovery wells. A SEAWAT model was developed to simulate coupled flow and heat transport. The model of a two-dimensional vertical cross section is able to simulate the temperature of the water at the well and the measured vertical temperature profiles reasonably well. MODPATH was used to compute flowpaths and the travel time distribution. At the study site, temporal variation of the pumping discharge was the dominant factor influencing the travel time distribution. For an equivalent system with a constant pumping rate, variations in the travel time distribution are caused by variations in the temperature-dependent viscosity. As a result, travel times increase in the winter, when a larger fraction of the water travels through the warmer, lower part of the aquifer, and decrease in the summer, when the upper part of the aquifer is warmer.

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Residence times in subsurface hydrological systems, introduction to the Special Issue

Cited by 11 publications

References 124 publications

Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Estimation of effective porosity in large-scale groundwater models by combining particle tracking, auto-calibration and <sup>14</sup>C dating

Estimating Travel Time in Bank Filtration Systems from a Numerical Model Based on DTS Measurements

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Residence times in subsurface hydrological systems, introduction to the Special Issue

Cited by 11 publications

References 124 publications

Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers

Estimation of effective porosity in large-scale groundwater models by combining particle tracking, auto-calibration and &lt;sup&gt;14&lt;/sup&gt;C dating

Estimating Travel Time in Bank Filtration Systems from a Numerical Model Based on DTS Measurements

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Estimation of effective porosity in large-scale groundwater models by combining particle tracking, auto-calibration and <sup>14</sup>C dating