TRANSIENT GROUNDWATER FLOW SURROUNDING A RECHARGE SLOUGH IN A TILL PLAIN

1986 ◽  
Vol 66 (1) ◽  
pp. 121-134 ◽  
Author(s):  
J. G. MILLS ◽  
M. A. ZWARICH
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Transient Flow ◽  
Flow System ◽  
Water Levels ◽  
Local Flow ◽  
Wide Range ◽  
Conductivity Water ◽  
Surface Saturation ◽  
The One

Knowledge of the groundwater flow system around a slough aids in the resolution of conflicting opinions on slough drainage. This study reports on the flow system around a typical temporary slough in a low relief till plain landscape. The site is located in a regional groundwater recharge area, with till of low hydraulic conductivity overlying a shale aquifer. The distribution of soil profile types in the landscape reflects a wide range of soil water regimes. Instrumentation at the site revealed an annual cycle of water levels and transient flow that was related to spring ponding of water in the slough. Numerical simulation of the flow system, under conditions of ponding, surface saturation, and evapotranspiration, helped to clarify and extend the field observations. Each depression in the landscape has a local flow system that is superimposed on the regional system. Hydraulic conductivity, water supply to the slough, and the amount and timing of infiltration and exfiltration all affect the local flow system. Temporary sloughs, such as the one studied, do not benefit agriculture, but drainage of these sloughs raises other concerns. Key words: Groundwater, transient flow, recharge, slough, pothole, simulation

Groundwater flow systems in the crystalline rocks of the Okanagan Highland, British Columbia

1968 ◽  
Vol 5 (4) ◽  
pp. 813-824 ◽  
Author(s):  
D. W. Lawson
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Flow System ◽  
Crystalline Rock ◽  
Crystalline Rocks ◽  
Two Dimensional ◽  
Local Flow ◽  
Groundwater Flow Systems ◽  
Flow Systems ◽  
Two Dimensional Flow

An investigation of the groundwater flow systems associated with the most prominent topographic expression in the Okanagan Highland (a U-shaped valley) revealed that the hydraulic conductivity of the crystalline rock varies exponentially with depth, and that the local flow systems within the upper 125 to 150 ft of the crystalline rock conduct an estimated 10 to 17 Imperial gallons per day per foot thickness in a two-dimensional flow system. These local flow systems are quantitatively the most significant in the Okanagan Highland.

scholarly journals The Effect of River Valleys and the Upper Cretaceous Aquitard on Regional Flow in the Dakota Aquifer in the Central Great Plains of Kansas and Southeastern Colorado

1995 ◽  
pp. 11-30
Author(s):  
P. Allen Macfarlane
Keyword(s):  
Hydraulic Conductivity ◽  
Great Plains ◽  
Upper Cretaceous ◽  
Flow System ◽  
Arkansas River ◽  
Local Flow ◽  
Discharge Area ◽  
Regional Flow ◽  
Regional Hydrogeology ◽  
Vertical Hydraulic Conductivity

In his reports on the regional hydrogeology of the central Great Plains, in particular southeastern Colorado and southwestern and central Kansas, Darton considered the Dakota aquifer to be a classic example of an artesian system. Computer simulations of the flow system in this study, however, suggest that the Dakota is not a regional artesian aquifer in the classic sense. Sensitivity analysis of a steady-state vertical profile flow model demonstrates that the flow system in the upper Dakota in western Kansas is heavily influenced by the Upper Cretaceous aquitard, the Arkansas River in southeastern Colorado, and rivers in central Kansas, such as the Saline, that have eroded through the aquitard and into the Dakota to the west of the main outcrop area of the aquifer. The model shows that local flow systems and the vertical hydraulic conductivity of the Upper Cretaceous aquitard heavily influence the water budget and the flow patterns. The aquitard restricts recharge from the overlying water table to underlying aquifers in western Kansas because of its considerable thickness and low vertical hydraulic conductivity. The Arkansas River intercepts ground-water flow moving toward western Kansas from recharge areas south of the river and further isolates the upper Dakota from sources of freshwater recharge. In central Kansas, the Saline River has reduced the distance between confined portions of the aquifer and its discharge area. In essence, this has improved the hydraulic connection between the confined aquifer and its discharge area, thus helping to generate subhydrostatic conditions in the upper Dakota upgradient of the river.

Groundwater age gradient to infer flow rates, hydraulic parameters, aquifer abstraction limits, and storage in the Wairau Plain, New Zealand

2020 ◽  
Author(s):  
Uwe Morgenstern ◽  
Mike Stewart
Keyword(s):  
Hydraulic Conductivity ◽  
Time Series Data ◽  
Flow System ◽  
Groundwater Age ◽  
Mean Transit Time ◽  
Water Levels ◽  
Estuarine Sediments ◽  
Series Data ◽  
Flow Rates ◽  
River Temperature

<p>Groundwater is an important source of water for the Wairau Plain, and there is concern about its sustainable yield because of declining water levels and spring flows in the Wairau Fan. The Wairau Fan is comprised of highly permeable fluvial gravels. The main source of groundwater is loss from the Wairau River channel. The underlying Pleistocene gravels form a significantly less permeable aquifer. Near the coast, estuarine sediments form an aquiclude over the Pleistocene gravels. The main groundwater flow from the gravel fan is forced back to the surface near the confinement boundary feeding highly valued streams with crystal-clear water but declining flow.</p><p>To understand the flow dynamics of the groundwater, we utilised tritium, SF6, and 14C. For the extremely young groundwaters in the unconfined Wairau Fan, <1 year, we developed a dating method that traces the seasonal river temperature variability through the aquifer. The lags of the temperature synodal signal were calibrated to true age via the <sup>18</sup>O synodal signal.</p><p>All groundwaters within the Pleistocene gravels are very old, >100 years, and up to 39,000 years in the Deep Wairau Aquifer. In contrast, throughout the unconfined Wairau Fan we observed only very young groundwater, with mean residence time of 0–1 years, even in the deeper wells of >20 m.</p><p>Flow rates estimated from groundwater age gradients show that in its upper part the unconfined Wairau Fan is well connected to the Wairau River. Extremely high flow rates of up to > 30 km/y in this area indicate extremely high hydraulic conductivity in these Holocene deposits near the river. Towards the coast, the flow rates reduce considerably, to 13 km/y at around the boundary of the confinement, thereafter slowing further to 0.7 km/y near the coast. The reduction in flow rate near the coast, by a factor >20, is related to the flow loss from the aquifer, mainly to the spring belt and through abstraction.</p><p>Hydraulic conductivities, derived from the flow rates, are c. 12,000 m/day in the unconfined Wairau Fan near the river and in the central part of the unconfined Wairau Fan. Near the coast the estimated hydraulic conductivity is 800 m/day. Despite relatively uniform hydraulic conductivities, the Wairau Fan becomes less transmissive downstream due to decreasing piezometric gradients. This is likely to cause the restriction in the flow system. The ‘choking point’ in the flow system of the unconfined Wairau Fan appears to be not the recharge zone near the river but the lower Wairau Fan due to its lower transmissivity by a factor of two.</p><p>To understand the buffer of the entire system against prolonged drought, the mean transit time of the water through the Wairau River catchment was estimated from tritium time-series data to four years, and the active groundwater storage to approximately 6,200M m<sup>3</sup>. The Wairau catchment would be able to maintain baseflow in the river and the aquifer for several years.</p>

Groundwater flow pattern and age distribution under transient conditions

2021 ◽  
Author(s):  
Menggui Jin ◽  
Yan Li ◽  
Jiale Wang ◽  
Xing Liang
Keyword(s):  
Probability Density Function ◽  
Groundwater Flow ◽  
Probability Density ◽  
Stagnation Point ◽  
Residence Time ◽  
Flow System ◽  
Local Flow ◽  
Groundwater Flow System ◽  
Flow Systems ◽  
Upper Boundary

<p>The distribution of groundwater ages under transient conditions are investigated by a numerical model coupled groundwater flow and age, and the nested pattern of groundwater flow are determined by the probability density function of residence time. The variation of local groundwater flow system to the fluctuation of upper boundary head evolves rapidly. During the process from the initial steady to the unsteady state, the groundwater age field evolves with simulation time and gradually reaches a new dynamic equilibrium after about 50 years. The age abrupt interface between the local and intermediate flow systems gradually shifts upward, and the scale of the local flow system gradually decreases. The groundwater ages of the regional and intermediate flow systems are mainly controlled by the long-term dynamic component of the upper boundary head, while the local flow systems are mainly influenced by the transient periodic fluctuation. The location of the stagnation points are mainly controlled by the upper boundary head. The larger head difference between recharge and discharge area is, the greater penetrated depth of the stagnation point is. The location of the stagnation point indicates the penetrated depth of the local flow system. The larger head fluctuates, the deeper stagnation point is, leading to a greater penetration depth of the local flow system. Molecular dispersion causes the scatters of residence time probability density function to aggregate near the inflection point, and the aggregation area mainly locates at the junction of basin-scale flow systems. The transition of groundwater flow field will intensify the mixing of old and new water, leading to the blurring or even disappearance of the residence time abrupt interface. The dispersion of groundwater mixing is poor in steady state, and the convective-dispersive effect gradually increases with time in unsteady state. Traditional hydraulics methods based on flow nets and stagnation points can effectively identify the groundwater flow system, but the differences in groundwater chemical characteristics and ages at long-term scales cannot be clearly described by these methods, as well as the evolution of groundwater flow system at long time scale. The groundwater residence time distribution expressed by the probability density function, which comprehensively involves the spatial and temporal information of groundwater interaction, can help accurately distinguish different groundwater flow systems at long time scales. The methods proposed in this study will act as a meaningful guidance for the delineation of groundwater flow system in the real world.</p>

The evolution and non-fickian flow of local stagnant zones in hierarchically nested groundwater flow system under different rainfall infiltration intensity

2021 ◽  
Author(s):  
Ronglin Sun ◽  
Liqun Jiang ◽  
Xing Liang ◽  
Menggui Jin
Keyword(s):  
Climate Change ◽  
Groundwater Flow ◽  
Flow System ◽  
Rainfall Infiltration ◽  
Stagnant Zone ◽  
Local Flow ◽  
Discharge Area ◽  
Directional Flow ◽  
Regional Flow ◽  
Flow Systems

<p>Groundwater plays an active role in certain geologic processes that has been recognized in numerous subdisciplines for a long time. According to Toth (1963, 2009), gravity-driven regional groundwater flow is induced by elevation differences in the water table and its pattern is self-organized into hierarchical sets of local, intermediate and regional flow systems.  Convergence of two flow systems results in a stagnant zone called hydraulic trap which is under the discharge area, and diverge of two flow systems results in a stagnant zone called quasi-stagnant zone which is under the water divide. These stagnant zones have been found to be critical to accumulation of transported mineral matter. Based on analytical and numerical solutions, some researchers reported that the local stagnant point or zone that are located under the local counter directional flow system. There is a question that whether hydraulic trap and quasi-stagnant zone is separate or integrate, and whether they are located under the discharge area or water divide or counter directional flow systems.</p><p>In this study, two-dimensional numerical cross-sectional model is used to investigate the effect of climate change on local stagnant zones and whether the hydraulic trap and quasi-stagnant zone is separate or integrate. Considering the climate change of basin and the change of rainfall infiltration intensity, a flux upper boundary is used to simulate the rainfall recharge. Then a synthetic homogeneous sandbox with three potential sinks is used to validate the evolution of the hierarchical nested groundwater flow systems considering different rainfall infiltration intensity. Salt tracer test is used to investigate the effect of stagnant zones on solute transport.</p><p>According to numerical results, we concluded that the hydraulic traps and quasi-stagnant are possible to be separate only for simple local systems and the two local stagnant zones are located on two sides of the counter directional flow system. When nested flow systems occur, such as local-intermediate, local-intermediate-local, local-regional, the local hydraulic traps and quasi-stagnant zones are always integrated under the local counter directional flow systems. Laboratory results show that when the rainfall infiltration intensity reduce, the groundwater flow pattern will change and the penetration depth and scope of counter directional local flow system will decrease. The corresponding local stagnant zone will slowly be closing to the discharge area of that counter directional local flow system. Salt tracer tests show that there are obvious non-fickian phenomenon in the local stagnant zones in hierarchically nested flow systems even in the homogeneous aquifer.</p>

Abnormal groundwater flow system between two rivers: a numerical investigation

2020 ◽  
Author(s):  
Li Ruoyi ◽  
Wang Xu-Sheng ◽  
Han Peng-Fei
Keyword(s):  
Groundwater Flow ◽  
Water Level ◽  
Flow System ◽  
Groundwater Discharge ◽  
Local Flow ◽  
Groundwater Flow System ◽  
Through Flow ◽  
Flow Systems ◽  
Pass Through ◽  
Infiltration Recharge

<p>Groundwater flow system has long been recognized as the local, intermediate and regional flow systems since Toth (1963). For groundwater flow in an unconfined aquifer between two parallel rivers (or ditches), as indicated by Hubbert (1940), there are two local flow systems contributing groundwater discharge to the two rivers from infiltration recharge. Surprisingly, this model has never been examined until Han et al. (2019) pointed out that something may be wrong: not only two flow systems exist. The problem was further investigated with a two-dimensional numerical model on MODFLOW for saturated groundwater flow below the arch-shape water table receiving a uniform infiltration recharge. Streamlines were obtained with MODPATH to identify the flow systems. We discovered that an abnormal groundwater flow system could emerge beneath the two local flow systems under some conditions, which forms a pass through flow from the high river to the low river. This pass-through flow system exists when the water level difference between the two rivers is sufficiently large and the infiltration recharge is sufficiently low. As a result, the base flow of the low river may be not only attributed to the captured infiltration recharge from the nearby local flow system but also partly originated from the high river. The ratio of the contribution from the pass-through flow system to the total groundwater discharge toward the low river could be higher than 20% and almost linearly increases with the water level difference between two rivers. More details of such an abnormal groundwater flow system were investigated as well.  </p>

scholarly journals Modeling Groundwater Flow System of a Drainage Basin in the Basement Complex Environment of Southwestern Nigera

2018 ◽  
Vol 1 ◽  
pp. 1-7
Author(s):  
Akinola S. Akinwumiju ◽  
Martins O. Olorunfemi
Keyword(s):  
Groundwater Flow ◽  
Drainage Basin ◽  
Flow System ◽  
Subsurface Water ◽  
Complex Environment ◽  
Basement Complex ◽  
Local Flow ◽  
Groundwater Flow System ◽  
Regional Flow ◽  
Flow Directions

This study attempted to model the groundwater flow system of a drainage basin within the Basement Complex environment of Southwestern Nigeria. Four groundwater models were derived from Vertical Electrical Sounding (VES) Data, remotely sensed data, geological information (hydrolineaments and lithology) and borehole data. Subsequently, two sub-surface (local and regional) flow systems were delineated in the study area. While the local flow system is controlled by surface topography, the regional flow system is controlled by the networks of intermediate and deep seated faults/fractures. The local flow system is characterized by convergence, divergence, inflow and outflow in places, while the regional flow system is dominated by NNE-SSW and W-E flow directions. Minor flow directions include NNW-SSE and E-W with possible linkages to the main flow-paths. The NNE-SSW regional flow system is a double open ended flow system with possible linkage to the Niger Trough. The W-E regional flow system is a single open ended system that originates within the study area (with possible linkage to the NNE-SSW regional flow system) and extends to Ikogosi in the adjoining drainage basin. Thus, the groundwater drainage basin of the study area is much larger and extensive than its surface drainage basin. The all year round flowing (perennial) rivers are linked to groundwater outcrops from faults/fractures and contact zones. Consequently, larger percentage of annual rainwater usually leaves the basin in form of runoff and base flow. Therefore, the basin is categorized as a donor basin but with suspected subsurface water input at its northeastern axis.

On the validity of the theory of flow in saturated swelling materials

Soil Research ◽  
1976 ◽  
Vol 14 (3) ◽  
pp. 389 ◽  
Author(s):  
DE Smiles
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Transient Flow ◽  
Initial Water Content ◽  
Approximate Theory ◽  
Initial Water ◽  
One Dimensional ◽  
Physically Based ◽  
Conductivity Water ◽  
The Relationship

Recently there has been concern that the reorientation of particles during transient flow of water in a saturated swelling material might result in the hydraulic conductivity and capillary potential not being well-defined functions of the water content. If this were the case, the conventional theory of one-dimensional liquid flow in these materials would be invalid. This paper shows that the hydraulic-conductivity/water-content relationship calculated using physically based approximate theory applied to outflow data obtained from red mud, is single-valued and independent of initial water content. Furthermore, the relationship permits recalculation, using a correct iterative procedure, of the data from which it was derived. It is concluded that the data provide no evidence to reject the theory, and that particle reorientation, if it occurs, is parametrized by the water content.

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

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