Modeling steady sea water intrusion with single-density groundwater codes

Area of Science:

• Hydrogeology
• Environmental Engineering
• Computational Fluid Dynamics

Background:

• Groundwater flow in heterogeneous aquifer systems often involves complex interfaces, particularly with saltwater intrusion.
• Simulating these interfaces accurately requires sophisticated numerical models, which can be computationally intensive.

Purpose of the Study:

• To develop and validate a transformation method for simulating steady-state interface flow in heterogeneous aquifers using single-density groundwater flow codes.
• To provide an efficient alternative to traditional transient saltwater intrusion modeling.

Main Methods:

• Transformed aquifer properties (hydraulic conductivity and thickness) are used to represent interface flow within single-density groundwater codes.
• The method involves adjusting parameters like aquifer base elevation and multiplying hydraulic conductivity by a density-dependent factor.
• The Ghyben-Herzberg formula is applied to determine the interface location, and specific code capabilities (e.g., MODFLOW) for handling unconfined flow and dry cells are discussed.

Main Results:

• The transformed model domains yield identical head and flow distributions compared to original models.
• The approach is validated against exact solutions and shows good agreement when using codes like MODFLOW.
• The method effectively simulates unconfined and confined multi-aquifer interface flow, including vertical leakage.

Conclusions:

• The proposed transformation technique offers an efficient and accurate method for simulating steady-state groundwater interface flow.
• This approach simplifies the modeling of saltwater intrusion by leveraging existing single-density groundwater flow codes.
• The study demonstrates the applicability and limitations of the method, particularly with MODFLOW, for heterogeneous aquifer systems.