Introduction to Hydrology (Geog 3511)

Fall 2012

Assignment 8: Material Properties of Soil Water in the Unsaturated Zone

Section | Lab | Assigned | Due |

012,013 | Tuesday | Tuesday, Oct 30 |
Friday, Nov 2 |

011 | Thursday | Thursday, Nov 1 |
Monday, Nov 5 |

40 possible points.

SHOW ALL YOUR WORK.

CITE SOURCES OF EQUATIONS USED.

WRITE THE QUESTION AT THE START OF EACH ANSWER.

Click here for a list of useful symbols

**We have collected a soil sample using a ** **
long cylindrical tube having a ** **
diameter. Wet weight of the soil sample was ** **.
After oven-drying at ** **
the sample weighed ** **.
Assume the particle density (** **)
was ** **. **

**Q1) What was the bulk density? **

**Q2) What was the porosity? **

**Q3) What was the water content? **

**Q4) What was the wetness (or degree of saturation)?**

**Use the following link to download pressure head and
volumetric moisture content data obtained from a fine sand. Data like
this are typically obtained from laboratory experiments.**

** DATA: pressure head vs
volumetric moisture**

**Q5) Graph pressure head (meters of water; x-axis) versus
volumetric moisture content (fraction; y-axis).**

**Q6) At what volumetric water content does the soil wetness
(S) equal 1? How did you figure this out?**

**Q7) What is the height of the capillary fringe? How did
you figure this out?**

**Q8) Is the volumetric water content of 0.05 less than,
equal to, or greater than the permanent wilting point? How did you
figure this out?**

**Q9) Graph volumetric moisture content (x-axis) versus
hydraulic conductivity (y-axis), using this data from a fine sand. Use
a linear-log plot, with hydraulic conductivity (y-axis) plotted on a
log scale.**

** DATA: volumetric
moisture content versus hydraulic conductivity**

**Q10) How does the hydraulic conductivity change with
increasing water content? **

**Q11) What is the hydraulic conductivity at Ksat? **

**Q12) What is the hydraulic conductivity at a pressure head
of -0.35 m? **

**Q13) What is the hydraulic conductivity at a pressure head
of -0.55 m?**

**Tensiometers are installed at 0.4 m and 0.5 m above the
water table in a uniform sandy soil with the moisture characteristic
and hydraulic conductivity curves from the two problems above. The
tensiometer readings are -0.45 m at 0.4 m above the water table and
-0.6 m at 0.5 m above the water table. Typical values of hydraulic
conductivity can be found in Dingman Table 6-1.**

**Q14) What is Darcy's Law? Give the equation and an
interpretation of each parameter. What is Darcy's law used for?**

**Q15) What is the hydraulic gradient (estimated from the
tensiometer measurements)? **

**Q16) Is the water movement up (towards the surface) or
down? Include your reasoning.**

**Q17) What is the moisture content at the 0.4 tensiometer? **

**Q18) What is the moisture content at the 0.5 tensiometer? **

**Q19) What is the hydraulic conductivity at the 0.4
tensiometer? **

**Q20) What is the hydraulic conductivity at the 0.5
tensiometer? **

**Q21) Calculate the specific discharge at the 0.4
tensiometer. **

**Q22) Calculate the specific discharge at the 0.5
tensiometer. **