Ground Water Level: Groundwater Levels and Drainage

Question 1

What is the phreatic level?

Answer 1

The phreatic level (or groundwater table) is the depth at which soil pores are completely saturated with water.

Question 2

What is the capillary fringe?

Answer 2

The capillary fringe is the zone above the groundwater table where water is drawn upward by capillary action.

Question 3

What factors affect groundwater seepage?

Answer 3

1. Soil permeability (higher permeability = faster seepage).
2. Hydraulic gradient (difference in water pressure).
3. Drainage conditions (open vs. closed systems).

Question 4

How does groundwater affect dikes and embankments?

Answer 4

High groundwater pressure can cause erosion, piping, and seepage, weakening dike stability.

Question 5

What are the stages of dike failure due to seepage?

Answer 5

1. Observation – Water appears behind the dike but no issue.
2. Wells – Water concentrated without sand movement.
3. Erosion – Sand and water mixture, risk of failure.
4. Severe Erosion – More than 1m³ of sand per well, possible dike collapse.