Semi-analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge

2020 ◽  
Vol 584 ◽  
pp. 124691 ◽  
Author(s):  
Mohammad M. Sedghi ◽  
Hongbin Zhan
Keyword(s):  
Analytical Solutions ◽  
Unconfined Aquifer ◽  
Discharge Variation

Diffusive contaminant transport in a multi-layered aquifer-aquitard system

2021 ◽  
Author(s):  
Seonggan Jang ◽  
Minjune Yang
Keyword(s):  
Analytical Solutions ◽  
Experimental Validation ◽  
Finite Thickness ◽  
Unconfined Aquifer ◽  
Flow Chamber ◽  
Measured Data ◽  
Solute Diffusion ◽  
Confined Aquifer ◽  
State Diffusion ◽  
Two Dimensional Flow

<p>A flow chamber experiment was conducted to investigate solute diffusion in a multi-layered aquifer-aquitard system. The two-dimensional flow chamber consisted of a finite thickness aquitard (kaolinite, 2 cm) bounded by two parallel aquifers at the top (unconfined aquifer, 2 cm) and bottom (confined aquifer, 4 cm). New Coccine (red dye) of 500 mg/L in the top aquifer and distilled water in the bottom aquifer were injected with 0.02 mL/min for 13 days. One-dimensional analytical solutions were developed for advection and diffusion through a finite aquitard and compared with the measured data to evaluate experimental validation. The simulated aquitard concentration profiles (E > 0.97) and breakthrough curve (E = 0.95) showed good agreement with the measured data. During the experiment, the penetration distance in the aquitard increased over time and the vertical concentration distribution showed a linear profile through the aquitard after 7 days of loading in the top aquifer, indicating steady-state diffusion. The New Coccine diffused across the aquitard to the bottom aquifer after 1 day of loading. The bottom aquifer concentration increased at early times and was maintained after 7 days of loading (11 ~ 12 mg/L). This study provides experimental validation of the developed analytical solutions and quantitatively evaluates contaminant occurrences of the confined aquifer through the aquitard.</p>

Écoulement saturé et non saturé de l’eau souterraine vers des drains en aquifère à nappe libre

2008 ◽  
Vol 45 (9) ◽  
pp. 1210-1223 ◽  
Author(s):  
Robert P. Chapuis ◽  
Adrienne Dénes
Keyword(s):  
Hydraulic Conductivity ◽  
Vadose Zone ◽  
Analytical Solutions ◽  
Unconfined Aquifer ◽  
Soil Characteristic ◽  
Flow Rates ◽  
Simplifying Assumptions ◽  
Construction Schedule ◽  
Engineering Projects ◽  
Unsaturated Seepage

The drainage of sports fields, highways, farm lands, and covers for wastes corresponds to the drainage of a shallow unconfined aquifer resting on a horizontal or sloping impervious substratum. The seepage, partly saturated and partly unsaturated, is thus described by nonlinear equations that are not easy to solve. A few analytical solutions exist; they were obtained after several simplifying assumptions. Are they realistic? In this paper, comparisons are made between predictions from analytical solutions and those from numerical resolutions (for saturated and unsaturated seepage) under steady and transient states. The analytical solutions predict a water table and flow rates that differ significantly from those of the numerical resolutions, and are sometimes unrealistic. Corrections to the analytical solutions have already been proposed to account for the vadose zone. Despite such corrections, the published solutions to drainage problems may be inaccurate. In engineering projects where the duration of drainage may be critical for the construction schedule, it is recommended to avoid the analytical equations and to use numerical codes that solve the complete differential equations by taking into account the complete soil characteristic curves for hydraulic conductivity and capillary retention, which can be obtained using permeability tests and capillary-retention tests.

scholarly journals Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 625
Author(s):  
Ran An ◽  
Pei Dong ◽  
Jun-Zhi Wang ◽  
Yifan Zhang ◽  
Xianfang Song ◽  
...  
Keyword(s):  
Water Flow ◽  
Water Table ◽  
Vadose Zone ◽  
Analytical Solutions ◽  
Air Flow ◽  
Thick Layer ◽  
Unconfined Aquifer ◽  
Positive Pressure ◽  
Low Permeability ◽  
Cap Layer

The rise and fall of the groundwater level can drive air flow in the vadose zone. In turn, the air flow can interact with the water flow. When the unconfined aquifer is covered by a low-permeability media, the coupling of the water flow and the air flow is more obvious. In this study, a conceptual model is established for coupling of air flow and water flow in the vadose zone in response to rapid fluctuations of the water table. Water injection and drainage experiments are conducted in a double-layered sand column with a thick layer (80.5 cm) of coarse sand and a thin layer of fine sand as a low-permeability cap. Different cap thickness (2 cm, 5 cm, 7.5 cm) and different thickness of the vadose zone (30 cm, 40 cm) are set for the experiments. Negative pressure (NP)/positive pressure (PP) of the air in the vadose zone is observed in the drainage/injection experiments, with higher pressure in experiments of thicker cap layer. In each experiment, NP or PP increases rapidly to reach a maximum in the early stage, and gradually becomes zero in the late stage. Analytical solutions on three subdivided stages indicate the permeability and thickness of the cap layer, as well as permeability and porosity of the media in the vadose zone are the key controlling factors on the process of coupling of air flow and water flow. The solutions also reveal the formation mechanism of air pressure in the vadose zone with a low-permeability cap. This study has both theoretical significance and engineering applications.

scholarly journals Integral transforms for three-dimensional pumping in confined, leaky, and unconfined aquifers

2021 ◽  
Vol 69 (3) ◽  
pp. 319-331
Author(s):  
Elizeu Melo da Silva ◽  
João N. N. Quaresma ◽  
Emanuel N. Macêdo ◽  
Renato M. Cotta
Keyword(s):  
Analytical Solutions ◽  
Integral Transform ◽  
Three Dimensional ◽  
Integral Transforms ◽  
Problem Formulation ◽  
Unconfined Aquifer ◽  
Physical Parameters ◽  
Unconfined Aquifers ◽  
Solution Verification ◽  
Pumping Rates

Abstract Analytical or hybrid numerical-analytical solutions based on the Generalized Integral Transform Technique (GITT) are obtained for the transient three-dimensional pumping problem of aquifers with a fully penetrating vertical well between two parallel streams. The problem formulation for confined and leaky aquifers allows for achieving exact analytical solutions through integral transforms, while the unconfined aquifer case introduces a fourth kind boundary condition which leads to a coupled transformed head ordinary differential system, that can be solved either analytically or numerically. A convergence analysis is performed to illustrate the consistency of the numerical results achieved for the head distribution, as well as for the related pumping rates. Results are obtained for selected cases and comparisons with literature results are performed. A solution verification confirms the agreement of the integral transform solutions with available simulations and provides additional confidence for the analysis of a few physical parameters that influence the hydrological behavior.

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