Surface Water Interaction Modelling Using Visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________11potential energy is also described as the hydraulic head – which is the sum of elevation and waterpressure divided by the weight density of water.The geology of an area governs movement and availability of surface and ground waters. Thepermeability of geologic materials and the intensity of precipitation determine the water flowsabove and below the land surface. Each geologic material exhibits its own permeability basedupon its chemical and structural composition.Much groundwater discharge into surface water is from local flow systems. Local flow systemsare the most dynamic and the shallowest flow systems; therefore, they have the greatestinterchange with surface water. Local flow system can be underlain by intermediate and regionalflow systems. Water in deeper flow systems have longer flow paths, but eventually discharge tosurface water and they can have a great effect on the chemistry of the receiving water.After rainfall events, materials with low permeability will cause water to pond whenever thewater input (recharge) exceeds the capacity of the materials to hold the water. Ponding of waterwill then cause water movement across the land surface and/or into the subsurface. Surfacemovement of water will follow elevation differences on the land surface, thus water willeventually spill into lakes, streams, rivers, etc. (Figure 3.1)Figure 3.1Flow through a Hypothetical aquifer system (GSFLOW model based on integration ofPRMS and MODFLOW 2005, Steven.L et.al USGS Techniques and methods 6-D1, 2008)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS