Groundwater model

Groundwater models are conceptual, analytical or numerical tools, which provide the necessary information for the quantitative and qualitative management of an aquifer available.

Generally

A groundwater model allows the simulation of different sizes as

• The flow field in the unsaturated or saturated soil area,
• The diffusive, dispersive and convective transport of dissolved substances in water ( transport model ) and the
• Heat propagation.

Mathematical Model

A mathematical groundwater flow model basically consists of a combination of the Darcy equation with a balance relationship, as it represents the Laplace equation, for example. A transport model is based on the calculated flow field and uses the advection- dispersion equation, a combination of the dispersion approach and a balance sheet relationship to calculate the spread of the water constituents. Alternatively, the calculation of the heat propagation in the flow field by means of the equation of heat conduction can take place.

Compulsory for the use of a mass transfer or heat propagation model is thus always the preliminary calculation of the flow field.

Numerical model

In addition to analytical solutions, such as the flow network, which mostly come from very simple ( one-dimensional or two-dimensional ) model concepts with simple geometric boundary conditions and homogeneous conditions in the model area, there are numerical models for the solution of the equations of the mathematical model.

Mathematical models are only approximately solved for practical applications with complex constraints, but allow the simulation of heterogeneous and anisotropic three-dimensional systems.

The solution with a numerical model is carried out either with the so-called Eulerian approaches such as the finite difference method, finite volume method or the finite element method or by Lagrangian approaches such as the particle tracking and the random walk method.

The groundwater model takes into account the geological and hydrogeological knowledge of the model area ( concept model or Hydrogeological model) or the requirements of an experimental setup. Part of a numerical groundwater modeling is the calibration of the model and performing a sensitivity analysis.

Calibration

The calibration, the verification of the calculated from the model results with the standard ( in practice: the measured field groundwater levels, concentrations or temperatures) results represents the difference between the measured to the calculated results as well as the groundwater balance of the model, the balanced wherever possible be is is a measure of the quality of the calibration, the stationary, ie time-independent, or non-stationary, that is, time-dependent, can occur.

Stochastic analysis

Since the underlying the model ( hydro) geological knowledge ( for example, the hydraulic permeability ) often ambiguous and especially can not be comprehensively quantified by field tests, it is advisable to vary these parameters in a sensitivity analysis, and thus their influence on the model results estimate.

Application

Based on the calibrated groundwater model to given conditions and model ideas using the calibrated parameter set checking, or simulated by the Verwending predicted, even time-dependent boundary conditions ( for example, groundwater recharge ), future trends, and the impact of planned human impact.