CE En 547 - Midterm Exam #1 KEY

Fall Semester 2017

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Multiple Choice

(1.5 pts each)

2. (head-darcy) Effective porosity is defined as:

a. The volume of saturated voids divided by the total volume
   
b. The volume of saturated voids divided by the volume of the soil
   
c. The volume of saturated voids divided by the total volume of voids
   
d. The volume of voids which contribute to flow divided by the total volume of voids
   
e. The volume of voids which contribute to flow divided by the volume of the soil
   
f. The volume of voids which contribute to flow divided by the total volume

3. (modflow) Which of the following statements is FALSE about the ET package?

a. The ET rate is assumed to be zero if the head is below a certain depth.
   
b. The ET rate varies linearly between the extinction depth and the ET surface.
   
c. As the head goes above the ET surface, the ET rate is zero.
   
d. All of the above are false.
   
e. None of the above are false

4. (modflow) Which of the following statements is true about the Well Package in MODFLOW?

a. A single cell cannot contain multiple wells.
   
b. A single cell can contain any number of wells.
   
c. A single cell can contain multiple wells only if the user sums the well fluxes to a single flux value.

5. (modflow) Which of the following curves best represents the relationship between the river-aquifer flow rate (Q) and the computed head (H) for a river object in MODFLOW? The head values increase from left to right. RBOT is the river bottom elevation and STAGE is the stage in the river cell.

a.
   
b.
   
c.
   
d.

6. (modflow) Which of the following MODFLOW packages would be best-suited for simulating the effect of a slurry trench cutoff wall on the flow field?

a. LPF
   
b. CHD
   
c. HFB
   
d. STW

7. (modflow) Which of the following best describes the primary difference between the Stream-Aquifer interaction (STR) package and the River (RIV) package in MODFLOW?

a. The RIV package limits the maximum head difference to the stage minus the bottom elevation if the head drops below the bottom elevation. With the STR package, the flow is always proportional to the total head difference.
   
b. With the RIV package, the user specifies the stage. With the STR package, the stage is calculated by MODFLOW based on the water budget and Manning's equation for each river reach.
   
c. With the RIV package, the water always flows from the river to the aquifer. With the STR package, the water can also flow from the aquifer to the river.
   
d. With the RIV package, the flow in the river is computed using Manning's equation. With the STR package, the flow rate is computed using the net flow budget.
   
e. None of the above

8. (modflow) MODFLOW was developed by:

a. The United States Bureau of Reclamation
   
b. The United States Geological Survey
   
c. The United States Soil Conservation Service
   
d. The United States Environmental Protection Agency
   
e. None of the above

9. (modflow) When calculating a conductance term for the River package using the general form (directly from Darcy's Law) of the conductance equation:



the "L" term in the denominator represents:

a. The length of the river reach in the cell.
   
b. The width of the river
   
c. The vertical thickness of the river bottom sediments
   
d. The "leakance" coefficient for the river bottom sediments
   
e. None of the above

10. (modflow) The units for the value of conductance required for individual cells for stress packages (River, Drain, General Head, etc.) in MODFLOW is:

a. [L]/[T^2]
   
b. [L]/[T]
   
c. [L^2]/[T]
   
d. [1]/[T]
   
e. None of the above

11. (goveq) The following governing differential equation applies to which of the following conditions (circle all that apply)?

a. steady state
   
b. transient
   
c. isotropic
   
d. anisotropic with the major axes of permeability aligned with the xyz coord. axes.
   
e. internal sources and sinks
   
f. none of the above

12. (modflow) Which of the following packages are optional? Mark all that apply.

a. Basic/Global
   
b. River
   
c. Well
   
d. Recharge
   
e. Flow Package (BCF, LPF, HUF)
   
f. Drain

13. (goveq) Select all of the conditions that are compatible with the following governing equation:

a. Isotropic
   
b. Kx, Ky, and Kz correspond to the major principal axes of permeability
   
c. Transient
   
d. External sources and sinks
   
e. 3D