3D Numerical Flow And Contaminant Transport Modelling

  

Numerical flow and contaminant transport modelling is one of the most specialised tools that we use in our groundwater studies and is normally used to consolidate all the findings of the baseline characterisation and as a platform from which to assess impacts from your operational activities on the surrounding aquifers and surface water bodies. We use a variety of internationally developed and recognised software packages based on either finite difference (MODFLOW) and finite element (Feflow) code depending on the project requirements.
 
Numerical groundwater flow and contaminant transport modelling is a powerful tool. It can be used to simulate the cumulative impacts on the surrounding groundwater environment from complex and dynamic processes such as those that would take place at a typical mining operation. The cumulative impacts from the proposed developments over time are simulated taking into account the influence of changes in groundwater quantities (for example through mine dewatering) and changes in groundwater quality from point or diffuse sources (for example a tailings dam or mined-out area).    

The numerical models are built around the conceptual groundwater flow model that is based on the baseline data collected during the study. This will include aspects such as:    

• The number and types of aquifers present in the area and their hydraulic interconnection;  

  

• The depths and yields of each of the aquifers; 
• Groundwater and piesometric levels;
• Aquifer parameters such as transmissivity, storage, and effective porosity;
• Recharge from rainfall;
• Groundwater / surface water interaction; and
• Features that control groundwater flows and contaminant migration such as dyke intrusions that act as flow barriers and fault zones that form preferential groundwater flowpaths.

Numerical models are typically applied to:    

• Simulate future impacts on groundwater levels, volumes and flow patterns due to removal (e.g. mine dewatering) or addition (e.g. artificial recharge into aquifers) of groundwater; 
• Simulate future impacts on groundwater qualities due to plume migration away from point and diffuse sources;
• Evaluate different mine closure scenarios and identify the optimum scenario from a groundwater quantity and quality point of view;
• Simulate historic impacts to identify pollution timelines and point sources;
• Evaluate different water management strategies and identify the optimum approach;
• Provide input into water balances by calculating the volume of groundwater that will seep into an excavation from the surrounding aquifers; and
• Design dewatering programmes including borehole depths, spatial distribution, number of boreholes, and pumping volumes and times.