By Professor Marek Zreda, University of Arizona, 10/3/2020  

Farmer Buck wants to install a new pump to aid in the irrigation of his crop of… (well, we couldn't tell you that or Farmer Buck would be in a lot of trouble!).  Buck's neighbor Willie doesn't want the new well to interfere with his own well's production.  Willie has said that he doesn't care how much Buck pumps as long it doesn't draw down the existing well by more than 0.5m.  It is up to you to maximize Buck's pumping rate without making Willie go dry.  Write a short report that describes how you set up your model and discusses your results.

You  know the following about the area:

  • There are 3 constant head boundaries and 3 impermeable boundaries
  • The basin is heterogeneous with 5 different units
  • Each unit is homogeneous
  • The area you should model is 2km x 2km.
  • The average land surface elevation in the area is 1500m
  • The average bottom elevation of the aquifer is 1450m 

MAGNET/Modeling Hints:

  • Use ‘Synthetic mode’ in MAGNET to create a model domain with the same dimensions as shown in the map
    •  Go to: 'Other Tools' > 'Utilities' > and click "Go to Synthetic Case Area' to access Synthetic mode. (Click OK to prompts that appear).
    • Once synthetic model domain appears, go to 'Utilities' > and click 'Geometry Locked' and then 'Geometry unlocked'. Then click anywhere inside the model domain. After answering OK to the prompts that appear, you will be able to click-drag any of the vertices to see the distance between vertices. NOTE: vertices are numbered and distances are indicated by d##, e.g., d21 is the distance from vertex 1 to vertex 2.
    •  Once you have the correct dimensions, you can click 'Geometry Locked' once more to lock-in the shape. 
  • Overlay the provided SiteMap image file included at the top of the problem description page (use the .jpg file).
    •  Go to: 'Other Tools' > 'Utilities' > 'Overlay myImage' and follow the instructions in the Help Page ('?' button)
    • Click the 'Use Domain Extent' button to fix the image to the established domain size. (This should be after choosing the image file but before clicking 'Upload'.)
  • Conceptualize the model as 1-layer aquifer. 
  • Use zone features to assign the appropriate hydraulic conductivity to each of the colored units shown above. The grey area can be parameterized with the domain hydraulic conductivity assigned in the Domain Attributes menu. 
  • Conceptualize the constant head boundaries using Line features; by default, the domain boundary follows a "no flow" condition (impermeable boundary)
  • Make sure you establish the equilibrium baseline flow before you turn on Buck's well!
  • Use a relatively fine grid to resolve the cone of depression due to pumping (e.g., Nx=80)
  • To analyze the head at a particular location in the model:
    • Go to: 'Analysis Tools' > 'Analysis' > and click 'NodalValues'.  Then, when you use the cursor to click anywhere on the map, a "flag" marker will appear. 
    • When you click on the flag, model results for that location will be shown in a pop-up window, including the simulated head.