# Soil Water

Set II   Soil Water
Gravitational potential is determined by the height of the points above the reference level.
Capillary or matric potential must be measured and, therefore, is provided.
Total potential energy is simply the sum of the component potentials.
Water flows from higher energy to lower energy.
The Gradient is determined by the _______ between the two points divided by the _____ between the points.
Multiplying the gradient by the hydraulic conductivity yields the total flow.
1. Soil water potentials:
100 cm
75 cm
50 cm
25 cm
0 cm
Note the soil diagram above. Point A is at 75 cm; point B is at 25 cm above the reference.
The capillary potential energy at point A is -100 cm.
The capillary potential energy at point B is -200 cm.
What is the total potential energy at point A? ______
What is the total potential energy at point B? ________
Will water flow between the points? _____ ___________________________
If so, in what direction? ____ _________
What is the gradient between the two points? ____ _______
If K = 10 cm/hr, determine the flow, Q between the points. __ __

2. Soil Water potential:
400 cm
300 cm
200 cm
100 cm
Note the soil diagram above. Point A is at 300 cm; point B is at 100 cm.
The capillary potential energy at point A is -400 cm.
The capillary potential energy at point B is -300 cm.
Note the reference level on the Figure
What is the gravitational potential energy at point B? _____________

What is the height of point A above the reference level? _________
What is the gravitational potential energy at point A? ___________
What is the total potential energy at point A? ___ ____
What is the total potential energy at point B? ______________
Will water flow between the points? _____ _______________________
If so, in what direction? _____ _____
What is the gradient between the two points? _ ____
If K = 5 cm/hr, determine the flow, Q between the points.

3. Soil Water potential:

400 cm
A
B Reference
300 cm
200 cm

100 cm

10 cm      20 cm
Note the soil diagram above. Points A and B are at 300 cm.
The capillary potential energy at point A is -200 cm
The capillary potential energy at point B is -100 cm.
Note the reference level for gravitational Potential.
Will water flow between the points? ________
If so, in what direction? __
What is the difference in total potential energy between the points? _
What is the gradient between the two points?____
If K = 10 cm/hr, determine the flow, Q between the points. _