Quantitative
6) A bucket (20 cm diameter by 10 cm depth) contains a loam soil with a particle density of 2.7
g/cm3 and a porosity of 40%. The soil is at a volumetric water content of 0.10. If the bucket
receives 2.0 cm of rainfall,
a. Determine the soil water content after the rainfall (you may assume that the rainfall
mixes uniformly throughout the soil volume).
Mass = density * volume
= 3.142 * 10*10*10
=3142cm3
=3142 * 2.7
= 8483.4 grams
Volume of the water
3.142 *10*10*2
=628.4cm3
Soil water content
Density = mass/volume
8483.4/628.4
=13.5
b. Determine the weight of the bucket of soil after the rainfall (you may disregard the
weight of the empty bucket).
Weight of the water
Mass = volume * density
3.142 *10*10*2*0.2
= 125.68 grams
Mass of the soil is 8483.4g
125.68 + 8483.4
=8,609.08 grams
7) A cylinder (4 cm diameter by 10 cm long) contains 210.0 g of oven-dry mineral soil. Estimate
the grams of water required to fully saturate the soil in the cylinder.
Density = mass/volume
3.142*2*2*10 = 125.68 cm3
210/125.68
= 1.67g/cm3
Volume is 1cm3
Mass = volume * density
=1*1.67
= 1.67 grams of water for every 1cm3
hence 125.68 cm3 * 1.67
=209.89 grams of water is needed to saturate the soil in the cylinder hence the soil water content is
1.67g/cm3
8) Suppose a layer of soil (20 cm thick, overlying impermeable bedrock) has a known θ(h)
Relationship
If the soil is initially at h= -1000 cm, how much rainfall would be required to increase h to -100 cm
throughout the soil layer? (You may assume that the added water is mixed uniformly throughout
the 20 cm layer and that there is no evaporation or drainage losses.)
11) a. What do you need to know in order to determine the direction of water flow between two
points?