An integrated three-dimensional surface water and groundwater model to simulate hydrodynamics and thermal and salinity transport

This paper presents the development and application of an integrated surface water and groundwater model to simulate hydrodynamics and thermal and salinity in tidal water bodies and subsurface media. The hydrodynamic module for tidal waters solves three-dimensional Navier-Stokes equations with or without the hydrostatic assumptions. Richards' equation is used to simulate the subsurface flow in both vadose and saturated zones. The boussinesq approximation is employed to deal with the buoyancy force due to temperature and salinity variations. The moving free surface is explicity handled by solving the kinematic boundary condition equation using a node-repositioning algorithm. The transport module solves the energy equation for temperature distribution and a mass transport equation for salinity fields. The Arbitrary Lagrangian-Eulerian (ALE) representation is adopted for all transport equations including momentum transport. The solution is obtained with finite element methods or a combination of finite element and Semi-Lagrangian (particle tracking) methods. The model is applied to Loxahatchee Estuaries for the investigation of its minimum flow requirements to maintain ecological balance.