Residence times and mixing of water in river banks: implications for recharge and groundwater–surface water exchange

Unland, Nicolaas Peter Hendrikus; Cartwright, Ian; Cendón, Dioni I.; Chisari, Robert

doi:10.5194/hess-18-5109-2014

Cited by 15 publications

(9 citation statements)

References 51 publications

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“…Leakage also appears to increase with proximity to the Tambo River, with generally greater EC responses at TU2 compared with TU5 and generally greater EC responses at TU1 compared with TU2. This is consistent with trends in isotope data at this site (Unland et al ., ). This effect of proximity is illustrated in Figure f, which suggests that an increase in groundwater elevation of 0.25 m is not significant enough to drive EC changes at TU5, minor changes at TU2 and significant changes at TU1.…”

Section: Discussionmentioning

confidence: 97%

“…Where the thickness of the confining layer is reduced, the thickness of the unconfined aquifer is increased (to a maximum of 26 m where the confining layer is absent). The hydraulic conductivities (K) of the unconfined aquifer and the confined aquifer are 3.0 × 10 À4 and 2.0 × 10 À5 m/s, respectively, which are the values estimated from the rising head tests (Unland et al, 2014). The hydraulic conductivity of the confining layer has been set at 1.0 × 10 À9 m/s, which is appropriate for clays (Freeze and Cherry, 1979).…”

Section: Data Collectionmentioning

confidence: 99%

“…As river EC at both the Bruthen and Tambo Upper transects is lower than groundwater EC and high EC waters through the area are dominated by Cl (Unland et al, 2014), which is largely conservative, the movement of river water into and out of the river bank can be traced using EC. Bank infiltration will occur when stream stage increases above groundwater elevation (Hantush et al, 2002;Sophocleous, 2002).…”

Section: The Dynamics Of Groundwater-surface Water Exchangementioning

confidence: 99%

“…In a companion paper (Unland et al, 2014), it was shown that the unconfined aquifer adjacent to the Tambo River in southeast Australia contains relatively young (<100 years old) and low-salinity groundwater. The observations that groundwater residence times and salinity increase towards the river are most consistent with regional groundwater inflows into the river banks rather than mixing between groundwater and river water.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic river–groundwater exchange in the presence of a saline, semi‐confined aquifer

Unland

Cartwright

Daly

et al. 2015

Hydrological Processes

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Understanding groundwater–surface water exchange in river banks is crucial for effective water management and a range of scientific disciplines. While there has been much research on bank storage, many studies assume idealized aquifer systems. This paper presents a field‐based study of the Tambo Catchment (southeast Australia) where the Tambo River interacts with both an unconfined aquifer containing relatively young and fresh groundwater (<500 μS/cm and <100 years old) and a semi‐confined artesian aquifer containing old and saline groundwater (electrical conductivity > 2500 μS/cm and >10 000 years old). Continuous groundwater elevation and electrical conductivity monitoring within the different aquifers and the river suggest that the degree of mixing between the two aquifers and the river varies significantly in response to changing hydrological conditions. Numerical modelling using MODFLOW and the solute transport package MT3DMS indicates that saline water in the river bank moves away from the river during flooding as hydraulic gradients reverse. This water then returns during flood recession as baseflow hydraulic gradients are re‐established. Modelling also indicates that the concentration of a simulated conservative groundwater solute can increase for up to ~34 days at distances of 20 and 40 m from the river in response to flood events approximately 10 m in height. For the same flood event, simulated solute concentrations within 10 m of the river increase for only ~15 days as the infiltrating low‐salinity river water drives groundwater dilution. Average groundwater fluxes to the river stretch estimated using Darcy's law were 7 m3/m/day compared with 26 and 3 m3/m/day for the same periods via mass balance using Radon (222Rn) and chloride (Cl), respectively. The study shows that by coupling numerical modelling with continuous groundwater–surface water monitoring, the transient nature of bank storage can be evaluated, leading to a better understanding of the hydrological system and better interpretation of hydrochemical data. Copyright © 2015 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 97%

Section: Data Collectionmentioning

confidence: 99%

Section: The Dynamics Of Groundwater-surface Water Exchangementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamic river–groundwater exchange in the presence of a saline, semi‐confined aquifer

Unland

Cartwright

Daly

et al. 2015

Hydrological Processes

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“…Well pumping in aquifers near streams may cause groundwater-surface water interactions (e.g., Rodriguez et al, 2013;Chen et al, 2013;Zhou et al, 2013;ExnerKittridge et al, 2014;Flipo et al, 2014;Unland et al, 2014). The stream depletion rate (SDR), commonly used to quantify stream water filtration into the adjacent aquifer, is defined as the ratio of the filtration rate to a pumping rate.…”

Section: C-s Huang Et Al: Approximate Analysis Of Three-dimensionamentioning

confidence: 99%

Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

Huang

Chen

Yeh

2016

Hydrol. Earth Syst. Sci.

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Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

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The impact of well drawdowns on the mixing process of river water and groundwater and water quality in a riverside well field, Northeast China

Zhu

Zhai

et al. 2019

Hydrological Processes

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Riverbank filtration (RBF) has been widely used throughout the world as an effective means to regulate surface water and groundwater resources and pretreat raw water for municipal water supply. The quality of the water from a riverside well field and the mixing ratios of surface water and groundwater is primarily impacted by the hydrodynamic processes in the RBF system. The RBF system is largely controlled by the water exploiting system in addition to the natural hydrologic condition of the river–aquifer system. As one of the most important design parameters of the riverside well field, the drawdown of groundwater level greatly determines the water head differences between the river water and groundwater as well as the field flow net, which subsequently impacts the mixing of river water and groundwater and water quality significantly. This study aimed to improve the understanding of the mixing process between the surface water and groundwater and estimate the impact of the RBF on the mixing ratio of surface water–groundwater and water quality quantitatively. A set of field pumping tests with various groundwater level drawdowns were carried out independently and successively at a riverside field with a single pumping well near the Songhua River in Northeast China in August 2017. During these tests, the water levels and hydrochemical parameters of the Songhua River, the adjacent aquifer, and the pumping well were monitored. The dynamic mixing process of the river water and groundwater and water quality under various drawdown conditions were analysed systematically using analytical methods. The results obtained from Dupuit method and the Mirror Image method in conjunction with the Hydrochemical Tracing method showed that the pumping water directly from the river water reached 60% ± 10% after a steady flow net was established. The larger the proportion of the pumping water captured from the river, the better quality of the pumping water was, because the quality of the river water (only limited to some water quality parameters monitored which were minority) was better than that of the groundwater. The results also showed that total Fe, TDS, total hardness, CODMn, and K+ were relatively sensitive to the changes of groundwater drawdown, and their concentrations decreased with an increase in the groundwater drawdown. It can be concluded that both the mixing ratio of the surface water and the groundwater and the water quality of the riverside well field can be regulated through adjusting the designed drawdown of the groundwater level, which is helpful for the design and the optimization of the riverside well water intake engineering.

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Residence times and mixing of water in river banks: implications for recharge and groundwater–surface water exchange

Cited by 15 publications

References 51 publications

Dynamic river–groundwater exchange in the presence of a saline, semi‐confined aquifer

Dynamic river–groundwater exchange in the presence of a saline, semi‐confined aquifer

Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

The impact of well drawdowns on the mixing process of river water and groundwater and water quality in a riverside well field, Northeast China

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