Question

Which among the followings provides the correct sequence of four zones of the infiltration profile (from top to bottom)?

• A. Transmission Zone - Wetting Zone - Transition Zone - Saturation Zone
• B. Saturation Zone - Transition Zone - Transmission Zone - Wetting Zone
• C. Transmission Zone - Transition Zone - Saturation Zone - Wetting Zone
• D. Wetting Zone - Transmission Zone - Transition Zone - Saturation Zone

Hint:

Water content is highest at the surface and falls sharply at the wetting front at the bottom.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
When water infiltrates into a dry soil column, it does not wet the whole profile at the same moisture level. It forms four fairly distinct zones from the surface downward, each with a different water content.

Step 2: Key Formula or Approach:
Starting from the surface where water enters, moisture content falls with depth in a fixed order. Knowing what each zone means lets us place them correctly.

Step 3: Detailed Explanation:
The saturation zone sits right at the surface, a thin layer that is fully saturated because that is where the water is entering.
Below it lies the transition zone, where water content drops off quickly over a short depth.
Next comes the transmission zone, a thick zone of fairly steady, unsaturated water content, this zone gets longer the longer irrigation continues, since it simply carries water down to the front.
At the very bottom lies the wetting zone, ending in the wetting front, where moisture content falls steeply to close to the original, dry soil moisture.
So reading top to bottom: saturation zone, transition zone, transmission zone, wetting zone.
Option 1 and option 4 both start from the wrong end, and option 3 leaves out the saturation zone at the top.

Step 4: Final Answer:
The correct top to bottom order is Saturation Zone, Transition Zone, Transmission Zone, Wetting Zone.
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