CE 473/573 Groundwater Fall 2011 Comments on homework 1

CE 473/573 Groundwater
Fall 2011
Comments on homework 1
1. Groups found interesting problems related to groundwater. Please see the compilation
for more details on these issues. Make sure to address the questions in the homework:
What is the effect of the engineering solution on the economy, environment, society,
etc.? What might you like to learn in CE 473/573 related to this problem?
2. I am not swayed by the argument of an ethanol plant simply continuing the natural
cycle of water. Groundwater naturally feeds surface water bodies, but if I built a
system to pump and transport Iowa’s groundwater into the Atlantic Ocean, I would
have a hard time arguing that what I am doing is “natural”.
3. Most groups had the right idea: Because the soil properties do not change, the difference in conductivities is due to differences in density and dynamic viscosity. Then
one can write
ρw μoil
ρoil μw
The conductivity of oil is lower than water’s because of the increased resistance caused
by the higher viscosity.
5. The main thing missing from the answers of most groups was a comparison of the
likely soil types determined from the value of K and the particle diameter. The
former suggests a well-sorted sand, while the latter suggests a silt. One improvement
in the model might be to try to relate the pore size and geometry to the particle size.
6. Most groups realized that larger values of K and d maximize the Reynolds number
and therefore give a conservative (i.e., safe) estimate.