1. **Porosity**: The ratio of the volume of voids (pores) to the total volume of the porous material. It is a measure of how much water the material can hold.
2. **Permeability**: A measure of the ability of a porous material to allow fluids to pass through it. It is influenced by factors such as the size and arrangement of pores.
3. **Hydraulic Conductivity**: The rate at which water can flow through a material, taking into account both permeability and the viscosity of water.
4. **Groundwater Flow**: The movement of water through the subsurface, driven by factors such as gravity, pressure gradients, and topography.
5. **Boundary Conditions**: The conditions at the edges of the model domain, which can include specified head (water level), specified flux (water flow rate), or no-flow boundaries.
- **Environmental Impact Assessment**: To evaluate the potential effects of human activities on groundwater systems.
- **Hydrological Modeling**: To simulate the overall water cycle, including surface water and groundwater interactions.
The model is often implemented using numerical methods, such as finite difference or finite element methods, to solve the governing equations of fluid flow in porous media. It requires input data such as geological and hydrological properties of the subsurface, as well as boundary conditions and initial conditions.