Among various software like Modflow, MikeSHE, ArcGIS etc. I wish to know the best for modelling the contaminate flow in groundwater from municipal solid waste dumping site.
The best code depends on what the objective(s) of your model is. Without more details, MODFLOW is widely used to simulate groundwater flow and MT3D can be used to simulate transport of contaminants from the landfill, if needed.
The best software for contaminate flow in groundwater depends on the objective and available input parameters for modelling. both ARC GIS , MODFLOW can use for modelling purpose.
The answer to the question 'best' depends upon the question you want to be answered using the numerical model. I can advise you that the choice 'best' also depends upon the amount of geological, hydrogeological, geochemical information available. Otherwise you can make the most simple model giving more information than the best and most complex model.
I agree that MODFLOW, FEFLOW, and ARCGIS are the most popular software for modeling contaminant flow in groundwater. It also s possible to visualize the contaminant plume using the 3D earth resistivity imaging tomography is the area is accessible and allows such survey.