Soil, Water, and Weather (SOIL 4683)
Solution for homework # 2
1. A cylindrical soil sample of 3.85 cm diameter and 10.00 cm height weights 201.13 g. The
sample is then oven dried at 105 oC until a constant weight, being 177.75 g, is reached.
Assuming the particle density of 2.65 g/cm3 and a density of water 1.00 g/cm3:
Calculate
The bulk density of the soil sample
Gravimetric and volumetric moisture content
Porosity
Equivalent depth of water contained in the soil sample
Solution
Volume of soil sample,
Bulk density of soil sample,
Gravimetric water content,
Volumetric water content,
⁄
⁄ ⁄
⁄
Porosity, f
⁄
( ) ( )
⁄
Equivalent depth of water,
⁄
Soil, Water, and Weather (SOIL 4683)
2. From the previous question, before oven drying how much water do we need to bring
the soil water content to 0.35m3/m3?
Solution
⁄ ; And ⁄
Change in equivalent depth of water = ⁄ * 10.00 cm = 1.5 cm = 15 mm
Total amount of water needed = = (= 17 ml of water)
3. Calculate the soil water storage in mm for a 25" deep soil profile in which the A horizon
is 10" thick and has a volumetric water content of 0.25 cm3 cm-3 and the B horizon is 15"
thick and has a volumetric water content of 0.35 cm3 cm-3.
Solution:
A = 10’’ ⁄
B = 15’’ ⁄
Soil water storage in the soil profile, S
( ⁄ ) ( ⁄ )
Soil, Water, and Weather (SOIL 4683)
4. Calculate the average volumetric water content after rainfall event for a 68 cm deep soil
profile which had an average volumetric water content of 0.27 cm3 cm-3 before getting
6.4 cm of rain. Assume 28% of the rain was lost to interception and there were no other
losses.
Solution
68cm
⁄ ⁄
