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Questions on Hydrogeology - Exam II | GEOL 127, Exams of Hydrogeology

Material Type: Exam; Class: HYDROGEOLOGY; Subject: Geology; University: California State University - Sacramento; Term: Fall 2006;

Typology: Exams

2009/2010

Uploaded on 03/28/2010

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Name _______________________________ Geology 127 (Hydrogeology)
Exam #2 Fall, 2006
Short answer questions (5 points each):
1) Define the water table in terms of atmospheric pressure and total hydrostatic pressure (words
only- no equations necessary!)
2) Draw a simple sketch to show the difference between an artesian well and a flowing artesian
well.
3) Which way do potentiometric lines bend (“v”) when they cross a losing stream? Illustrate
your answer.
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Name _______________________________ Geology 127 (Hydrogeology) Exam #2 Fall, 2006 Short answer questions (5 points each):

  1. Define the water table in terms of atmospheric pressure and total hydrostatic pressure (words only- no equations necessary!)
  2. Draw a simple sketch to show the difference between an artesian well and a flowing artesian well.
  3. Which way do potentiometric lines bend (“v”) when they cross a losing stream? Illustrate your answer.
  1. How is vertical hydraulic gradient calculated? Draw two wells and label variables to explain your answer.
  2. A monitoring well is fully penetrating, but the nearby pumping well only extends through 90% of the aquifer. These wells are 150 m apart, the aquifer is 10 m thick, and the aquifer is essentially isotropic. Are assumptions about radial flow to the pumping well valid in this case? Why or why not?
  3. How would you model (predict) drawdown in a pumping well that is located near an impermeable boundary? Draw a sketch to show how multiple wells could be used to solve this problem.
  1. A confined aquifer consists of a sandy interval that is 25.3 ft thick. Two wells that are completed in this aquifer are 1018 m apart (along the trend of the groundwater flow lines). The potentiometric surface drops 2.25 m between these wells, and the hydraulic conductivity of the aquifer is 55 m/d. How much water is moving through the aquifer per unit width? (10 points) 8b) If the aquifer is a buried stream deposit that extends laterally for 5400 m to the edge of the valley wall, how much water is flowing through the entire unit? (5 points)
  1. A monitoring well has a land surface elevation of 29.15 ft, and is 27.00 ft deep. Depth to water is 15.27 ft. What is the pressure head in this well? What is the elevation head? What is the total hydraulic head? Assume that the screen length is short enough so that it does not affect your calculations. Draw a simple sketch to illustrate your answer. (10 points) 9b) If the water in the well is salt water with a density of 1024.505 gm/cm3 at a temperature of 14° C, and the density of fresh water at an equivalent temperature is 999.244 gm/cm3, what is the equivalent freshwater pressure head? What is the total equivalent freshwater head? Show all work. (5 points)
  1. A large agricultural supply well is installed in a completely confined aquifer. The confined interval has a transmissivity of 2975 ft^2 /d, aquifer thickness of 255 ft, and a storativity of 0.0002. During a test, the well was pumped at 750 gpm for 21 days. The farmer wants to know if his well is likely to impact a neighboring well that is 3000 (3.0 x 10^3 ) ft away. How much drawdown would you predict in the remote well? Show all work. (20 points)