Physical Geology Helpful Lab Hints
Guide to the Sand Hills of Nebraska, map
Exercise 9, Problem 1:
a. Contouring is discussed on page 100. You are drawing lines of equal elevation above sea level on the groundwater surface, so ignore the brown contour lines and other indications of surface elevation.
b. Two part question. Look at the contour lines you drew for a.; which way is down hill? For the gradient, select two lakes on opposite sides of the map. The gradient is the difference in lake elevation divided by the distance between the two lakes.
c. Use the equation on page 163. Do what the hint suggests (Divide feet/mile from b. by the number of feet in a mile.) You will get a very small number (your calculator may display the number in scientific notation).
d. If V=d/t, then t = d/V. You determined velocity (c.) they give you the distance in cm. The result will be in seconds (and will be very large); divided by the number of seconds in a minute, minutes in an hour, hours in a day, and days in a year to give you the number of years. How long will it take for groundwater to travel across the map?
e. Use the contours you drew (a.) to compare the surface elevation to the groundwater elevation.