Introduction to Hydrology (Geog 3511)

Fall 2012

Assignment 7: GROUNDWATER

Section | Lab | Assigned | Due |

012, 013 | Tuesday | Tuesday, Oct 23 |
Friday, Oct 26 |

011 | Thursday | Thursday, Oct 25 | Monday, Oct 29 |

40 possible points.

SHOW ALL YOUR WORK.

CITE SOURCES OF EQUATIONS USED.

WRITE THE QUESTION AT THE START OF EACH ANSWER.

TYPE YOUR LAB UP

**Q1) Calculate the vertical flow rate (Q) using Darcy's Law for the
following sandstone block. (3 points)**

**A equals 1.5 m x 1.5 m **

**the change in elevation is (** **)
is ** **
**

** is
**

** is
** **
**

** is **
**day**

**Q2) Calculate the flow rate (Q) using Darcy's Law for a
silt block. All parameters are the same except that ** ** for
silt is ** ** **
**day.
(3 points)**

**Q3) Over a 24-hr period, how much more water moves through
the sandstone block compared to the silt block? (2 points)**

**Q4) Which of these formations would be considered an
aquifer and which an aquiclude? Why? (2 points)**

**Given the following unconfined aquifer system: **

**The average width (** **) is **
** km **

**The length (** **) is **
**
km**

**The average thickness (** **) is **
** m **

**Hydraulic conductivity (** )** is **
** m/day
**

**The elevation at point 1 (** **)
is ** ** m **

**The elevation at point 2 (** **)
is ** ** m **

**Q5) Calculate the horizontal flow rate (** **)
using Darcy's Law. The following image is a schematic of an unconfined
aquifer from the San Luis Valley in Colorado. Which way is the water
flowing and why? **

**Be sure to show all formulas and the calculations for each
parameter in the formulas. (3 points)**

**Q6) What is the transmissivity of the aquifer in Q5? (2
points)**

**Q7) Two piezometers are installed in the unconfined
aquifer. Calculate the hydraulic gradient using the data from
piezometers A and B. Which way is the water flowing? Use ** ** from Q5. How would you use this information to calculate specific discharge? (4 points)**

**Piezometer A, land surface is 450 m above the datum, depth
to water is 75 m.**

**Piezometer B, land surface is 450 m above the datum, depth
to water is 150 m. **

**The distance between A and B is 300 m. **

**Following is an image of a plan view of a field of
piezometers. Hydraulic heads at each of the wells are as follows: **

**A = 375 m **

**B = 300 m **

**C = 375 m **

**D = 400 m **

**E = 375 m **

**F = 300 m **

**Print out the image. **

**Q8) Add the values for hydraulic head to each of the wells
**

**Q9) Draw equipotential lines at 300 m, 375 m, and 400 m.
Use solid lines. **

**Q10) Draw three flowlines perpendicular to the
equipotential lines, using dashed lines. One line should be to the left
of C, one line should be between C and E, and one line should be to the
right of the E. **

**Q11) On each flow, add an arrow indicating direction of
flow. **

**Lets apply our new understanding of groundwater flow to
investigate a general assumption that groundwater losses from a
catchment are negligible. We'll use some data from Nel Caine's research
on the Martinelli catchment on Niwot Ridge. The Martinelli catchment is
a small (8-ha) alpine basin with colluvium deposits at the basin outlet
where the gaging station is located. **

**Data available:**

**a) Two wells located 10 m apart, in a line perpendicular
to the stream. **

**b) The water table is 5 m lower at the well closest to the
stream than at the well further away from the stream.**

**c) The saturated thickness of the colluvium deposit is 3
m. **

**d) The length (along the stream) of the colluvium deposit
is 20 m. **

**e) Saturated hydraulic conductivity is 0.15 m/day. **

**f) Stream discharge (** **)
was 25 m** ** on
21 August 1986. **

**Q12) What is the hydraulic gradient in the horizontal
direction? (2 points)**

**Q13) What is the transmissivity? (2 points)**

**Q14) What is the volume of groundwater discharged for 21
August 1986 in cubic meters? (3 points)**

**Q15) What is the ratio of groundwater discharge to stream
discharge for that day? (2 points)**

**Q16) In the simplified hydraulic equation (drats, vertical
learning), ** **
and the groundwater component (** ** or **
**)
is ignored. Is that assumption valid here? Why or why not? (2 points)**