Ground water modelling

Ground water plays an important role in the transport of pollutants in the environment. The movement of groundwater (and thus, pollutant transport) is governed by a number of processes. Geological characteristics, e.g. fracture zones in the bedrock, aquifers in the soft/ soil layers such as eskers influence the presence of ground water. Hydrogeological factors, such as ground water formation and the permeability of a certain geological material, determine the rate and pathways of ground water flow. The chemical and physical properties of the groundwater, pollutant and the geological materials, such as solubility, sorption mechanisms, and the density of water, govern the spreading of the pollutant. Multiple phase flow may occur with some pollutants, for example when insoluble liquids do not mix with the ground water or when gases are transported through the soil. Models can be constructed to represent the relevant environmental characteristics and processes, allowing calculations to be performed to evaluate pollutant transport and to analyse the importance of different factors and processes. However simplifications must be made, as reality never can be completely described. The model should focus on the most significant processes for each specific case. Kemakta has the competence to carry out model calculations and evaluate the results in order to facilitate the assessment of a pollution problem. Groundwater modelling also forms an important basis for transport calculations performed within safety assessment of final repositories for spent nuclear waste and hazardous chemicals. Kemakta has a long experience of this type of modelling.

Different pollution problems demand different models. Kemakta has at its disposal a number of different models, including those presented on this page.

General models GMS: Can handle both stationary and non-stationary flow calculations. Simulations can be made in both 2D and 3D. TWODAN - Simple 2D model suitable for simple problems, e.g. to illustrate flow paths. Unsaturated multiple phase. TRUST/TOUGH - TRUST is good for unsaturated flow and TOUGH calculates multiple phase flow. They are most suitable for 2D modelling.

Stochastic models HYDRASTAR - Restricted to flow in a 3D stochastic continuum. CHAN3D - Stochastic 3D network of 1D channels. Calculates flow and transport.

The figures show the main stages in the process of ground water.

Description of the problem, e.g. topography, contaminants, stratigraphy, hydrology, climate

Construction of a conceptual model, simplification of reality.

Calculations are carried out with the model, and the result evaluated and presented in a graphic form.