Unit 1: Water In Soil

Question 1

Differentiate between Groundwater and Groundwater table (GWT)?

Answer 1

• Groundwater - all the water found underground, in the cracks and spaces in soil and rock.
• Groundwater table - an underground boundary where soil and rocks are filled with water. It changes with time depending on the season of the year.

Question 2

What is the portion below the GWT and the portion above?

Answer 2

• Phreatic zone - the portion below the GWT.
• Vadose zone - the portion above the GWT.

Question 3

What are the three types of groundwater flow?

Answer 3

1D Flow (parallel vectors), 2D Flow (plane-constrained), 3D Flow (varies in all directions).

Question 4

What is the difference between steady and unsteady groundwater flow?

Answer 4

Steady flow remains constant over time, while unsteady flow changes over time.

Question 5

What is soil permeability and how is it caused?

Answer 5

The capacity of soil to allow water to pass through it. This is due to the existence of interconnected voids through which water flows from points of high energy to points of low energy.

Question 6

Define the permeability of the following substances: gravels, clay and rock.

Answer 6

• Gravel: highly pervious - water flows through easily.

• Clay: impervious - water cannot flow through easily.

• Rock: impermeable - water cannot flow through at all.

Question 7

What is permeability?

Answer 7

The ability of soil to allow water flow, measured by the coefficient of permeability (k).

Question 8

What factors affect soil permeability?

Answer 8

1. Porosity
2. Particle size & shape
3. Degree of saturation
4. Clay mineral properties
5. Water viscosity

Question 9

What is the main difference between the constant-head and falling-head tests?

Answer 9

• Constant-Head Test: Used for coarse soils, water flows at a steady rate.
• Falling-Head Test: Used for fine soils, water level drops over time.