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Accurate Estimation of Initial Saltwater-freshwater Interface for Simulating Saltwater Intrusion using numerical methods
  • Subhajit Dey,
  • om Prakash
Subhajit Dey
Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihta-801103

Corresponding Author:[email protected]

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om Prakash
Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihta-801103
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Abstract

Coastal aquifers are prone to saltwater intrusion as increased demand for freshwater leads to heavy, unregulated pumping from these coastal aquifers. Under sustainable pumping conditions, the saltwater-freshwater interface is stable but rarely monitored. When saltwater intrusion is first detected, saltwater-freshwater interface is already disturbed and starts moving inland. Any numerical simulation-based methodology to manage saltwater intrusion requires the initial saltwater-freshwater interface to be known. Numerical models need to satisfy the boundary conditions and the initial conditions (Cauchy–Riemann equation) for the solution to exist. However, in the absence of any monitoring, the initial position of the saltwater-freshwater interface is unknown, which forms the initial condition for numerical models and thus fall in the category of initial value problem. Pool and Carrera’s correction factor for the sharp interface approach is used to estimate the initial saltwater-freshwater interface. Generally, groundwater head information is readily available, which can be used to locate the saltwater-freshwater interface. Ghyben-Herzberg relation is used for estimating the initial position of the interface, but the level of accuracy of the information derived from Ghyben-Herzberg relation is low. Hence, in this study Pool and Carrera’s correction factor for density ratio is used in Ghyben-Herzberg relation for accurate estimation initial interface location. The developed method is applied to a real coastal site in Puri, India, where the aquifer is encroached by saltwater intrusion. The performance evaluation results show the applicability of this methodology