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 Koil = Kw 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.