There are instances when we are interested in groundwater conditions in different geological layers (sometimes called hydrostratigraphic units) - or how a leaky confining layer impacts groundwater conditions in an adjacent aquifer layer.  These situations require a 3D model with two or more aquifer layers.  Other times, we may need to resolve vertical processes within one or more aquifer layers (e.g., flow around a subsurface barrier or infrastructure, contaminant transport prediction, etc.). 

MAGNET enables flexible, interactive implementation of both types of 3D modeling approaches. When sub-dividing one or more aquifer layers into multiple vertical (computational) layers, an iterative, curvilinear vertical discretization scheme is used. First the model is discretized using one computational layer for each aquifer layer to solve the head distribution, which is then used in the next iteration to subdivide the saturated thickness of the aquifer(s) into multiple computational layers, say 2 or 3, which are solved. The process is repeated until a steady-state head distribution is solved for the desired number of total computational layers. The resulting layer configuration is then used for further simulation (e.g., transient modeling). 

TASKS

A - Study the step by step short video tutorial under MAGNET Quick Tutorials: 3D Flow, Multiple Computational Layers

B -  Develop a MAGNET model that reproduces the simulation as depicted in the tutorial.

C - Study the step by step short video tutorial under MAGNET Quick Tutorials: Aquifer Layers

D -  Develop a MAGNET model that reproduces the simulation as depicted in the tutorial.

E - Now visit the Woburn superfund site problem on the MAGNET Curriculum Network. This problem requires students to build a model with 3 aquifer layers (conceptual layers) to represent the groundwater conditions in the valley filled with unconsolidated glacial sediments. 

• Explain how you might create an 'equivalent' 3D model using one conceptual layer with 3D zones of different K (Hint: review the partial penetration elevation feature). 
• Discuss the realtive advantages and disadvanages of the two approaches for representing 3D groundwater conditions.