Analytical Solution for Multi-well System of Groundwater Remediation in the vicinity of a Permanent Stream

Document Type : Original Research

Authors
A. Ramezani-Charmahineh 1
M. Asadi-Aghbolaghi 2
R. Mirabbasi Najafabadi 2
S. Tabatabaei 2
1 PhD Student of Water Resources, Department of Water Engineering, Shahrekord University
2 Associate Professor, Department of Water Engineering, Shahrekord University
A-10-12232-4
Abstract
Human civilizations have always depended on freshwater to form, develop and fulfillment of various needs. With increasing urbanization, not only has the need for freshwater not diminished, but also some new technologies and industries have increased water consumption, and the pollution of water sources has increased significantly. Since groundwater resources are far from surface pollution and have their natural remediation ability, protection and remediation have not been given sufficient and appropriate attention. This issue and the overexploitation of aquifers have resulted in the quantitative and qualitative balance of groundwater resources being unsustainable. These issues show that further research is needed on various aspects of groundwater remediation. By developing the equations for water movement in porous media and analyzing them, it is possible to simulate groundwater flow. In this study, the double-well pumping system has been investigated analytically as one of the effective methods for aquifer remediation. In this system, pumping wells provide a return to natural conditions by draining polluted water and preventing it from spreading in the aquifer. For this purpose, the equations of the groundwater potential function and the stream function were determined for two pumping wells near a permanent stream. In other words, the real part of the complex potential equation represents the potential function and its imaginary part specifies the stream function; using the image well theory, the effect of the stream was also applied in the problem relations. By determining the coordinates of the stagnation points, the capture zone of the multi-well system was delineated in various configurations and the amount of stream withdrawal was also calculated. The capture zone describes the behavior and capability of the multi-well system by indicating the capture domain of discharge wells for different distances and different pumping rates. Three configurations of the remediation system are presented for two types of critical pumping rates. Under these conditions, it is possible to control the capture zone without intercepting the stream boundary and creating gaps in the extraction region at different distances of the wells with certain pumping rates. At the first critical pumping rate, the capture zone of the double-well system is tangent to the permanent stream boundary, and at a pumping rate below this threshold, groundwater pollution does not reach the surface waters. At the second critical pumping rate, capture zones of two wells merge together. Indeed, in discharges less than this critical rate, there is a distance (gap) between capture zones of the wells and pollution can enter the surface water through this gap. Also, the distance between two wells was determined in the state that both types of critical pumping rate are equal. This case shows a state of capture zone whose boundary is tangent to the stream boundary, and the capture zones of two wells are merged together. In the mentioned state, the dimensionless distance between two pumping wells (the distance between the two wells divided by their distance from the stream boundary) and the dimensionless critical pumping rate are equal to 2×0.58 and 0.33, respectively.

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Modares Civil Engineering journal
Volume 24, Issue 2
May and June 2024
Pages 125-138