Exercise - Darcy's Law Calculations

Part 1 - Travel Time Problem

You have been hired as a consultant for the Hanford DOE site in Washington state and you are reviewing the output from a groundwater model developed as part of an earlier study. The computed heads and pathlines from the model are shown below. You are asked what is the minimum travel time from the 200 west site to the Columbia river. Assume that the length of the flow path shown on the diagram is 20 miles. The head contours are in meters. The hydraulic conductivity is 150 ft/day and the porosity is 0.3. What is your answer?

Solution: columbia_key.md

Solution file (ppt): columbia (key).pptx

Part 2 - Travel Time

Consider the following flow path:

The water level in an observation well A is measured at 1274.4 m. At a point 406 m downgradient from that point, the water level in a second well (B) is measured at 1258.3 m.
a. What is the hydraulic gradient between well A and well B?
b. Assuming that the hydraulic conductivity is 1 m/day and the effective porosity is 0.15, what is the seepage velocity between the two point? [m/day]
c. How long would it take for a particle to travel from well A to well B? [days]

Excel starter file: darcy.xlsx

Excel solution: darcy (key).xlsx

Part 3 - Flow Volumes

Consider the following cylinder:

Water is flowing through the column of soil on the left. Assume that the cross-sectional area of the column = 0.8 ft^2 and K = 8.5 ft/day. How much water will flow through the column in 5 days time?

Excel starter file: darcy.xlsx

Excel solution: darcy (key).xlsx