Aquifer heterogeneity Aquifers Experimental and numerical methods Groundwater contamination Groundwater pollution Groundwater resources High-to-low Hydrogeology Image analysis Image-analysis Low permeability zone Mixing zones Numerical methods Refraction SUTRA Saline water intrusion Salt water intrusion Seawater Steady state aquifer aquifer heterogeneity groundwater contamination groundwater pollution hydraulic conductivity image analysis permeability saline intrusion saline water intrusion seawater