Objectives 1
Department of Earth Science |Northeastern Illinois University

ESCI 337
Spring, 2009

Daily Objectives #22 (April 14, 2009)                                        Dr. Sanders

By the end of today's class, you should be able to do the following: 
Complete your modeling project paper:

n Use scientific language.  (use third person, "impersonal", active voice as much as possible.   But when necessary, to avoid the use of "I" or "we", it's okay to use passive voice.)
n Cite all sources of information that did not come out of your own brain.
n Use headings and sub-headings to help the reader organize the information.

n Include the following information, in the order described below.

A) The report itself, compiled into a coherent document:

    1) Your Recommendations to your clients.  (How many wells will they need?  Where should they be placed?  How deep should they be?  What should their pumping rates be?)

    2) A statement of the Objectives of your study.

    3) The information you wrote on the Geology of the Study Area.

    4) A map showing the line of cross section.  Eliminate extraneous material!  (Trim it off.)  Be sure your map shows the line along which the cross section is drawn; it also should give the numbers of the borings used in the cross section.  Don't forget to label A and A'.

    5) Your finished cross section of the study area.  (Do not turn in the original!  Correct any errors or re-draw whatever is needed; then make a photocopy on 11" x 17" paper.  This version will not show the grid lines, and that makes for a neater presentation.)

    6) Your description of the numerical model.  Include these components:
         a) Explanation of the conceptual model for the study area.  Include a very brief (a few lines each) discussion about each of these components:
                 i) The hydrostratigraphy of the study area
                ii) The boundaries to the flow system
               iii) The stresses to the flow system (recharge, pumping)

         b)  Your list of the variables in the model, telling in no more than a few sentences each why you chose the values you did. 

         c) A few sentences telling what the results of the model (equipotential lines and particle tracking) show for the study area. 

         d) A few sentences describing the results of you sensitivity analysis (see below).  (Which variables is the model most sensitive to?)

     7) Discusson: A few lines explaining why you recommend the number, depth, placement, and pumping rates of wells described in the Recommendations.

B) The model itself.  Please save your completed model as "yourname.ggw".   E-mail it to me as an attachment.
Ground Water Modeling: Practice

     Perform a sensitivity analysis of your model:

Try changing some variables and see what happens.  Consider how good your estimates are.  How reliable is your estimate of, for example, hydraulic conductivity?  Could the actual value reasonably be higher?  Lower?  By how much?  Change the values and re-run the model; see how the results differ.  Here are some suggested approaches; keep notes on your work, as you'll need it to write up your results later. 

  • top elevation of the aquifer:  How close to reality do you think your input data are?  What happens if you change them?
  • bottom elevation of the aquifer:  What if these data were changed?  What would the results look like?
  • hydraulic conductivity:  What's a reasonable range of possible values?  How much difference does it make?
  • recharge to the aquifer through infiltration:  What if recharge is doubled?  Halved?
  • porosity:  What difference would it make if the porosity were 30%?  20%?  Some other value?
  • initial head:  How does changing initial heads change the model results?  (Consider the constant head cells and active cells separately.)
  • rate of pumping from wells:  What if your clients' industrial production increases, and they need to increase pumping of the wells by 20%?  50%?
Finally, now that you know the effect of changing each variable, rate the effect as "strong", "moderate", or "minimal".  You may wish to use this document to help yourself organize your results. 

Department of Earth Science | Northeastern Illinois University

Copyright 2009 Laura L. Sanders.  Last updated April 14, 2009.