Arrange the various zones of distribution of soil moisture in the infiltration process. A. Saturation zone B. Wetting zone C. Transmission zone D. Transition zone
- AA, B, C, D
- BC, D, B, A
- CA, D, C, BCorrect
- DC, A, D, B
Solution
Concept
During infiltration, soil moisture zones from the ground surface downward are: saturation, transition, transmission, wetting zone (then wetting front).
Step-by-step solution
1. At the top, just below the ground surface, the soil is fully saturated: Saturation zone (A) 2. Below it, moisture content drops quickly: Transition zone (D) 3. Next, a thick zone with nearly uniform moisture: Transmission zone (C) 4. Then moisture drops sharply near the front: Wetting zone (B) 5. Order = A, D, C, B
Explanation
Water enters from the top, so the top layer is saturated first. Below come the transition zone, the long transmission zone, and then the wetting zone that ends at the wetting front. So the correct order is A, D, C, B.
Why the other options are wrong
Option A puts the wetting zone second, but it is the deepest zone. Option B starts with the transmission zone, but the top layer is saturated. Option D puts the transmission zone above the saturation zone, which is wrong.
Shortcut
Remember 'S-T-T-W': Saturation, Transition, Transmission, Wetting (top to bottom).
Common mistake
Mixing up transition and transmission. Transition is the thin layer just below the saturation zone.
Correct answer: C) A, D, C, B