Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: The zone of aeration consists of three belts viz., (1) soil water belt (2) intermediate belt and (3) capillary fringe. Reason R: In the zone of saturation all the macropores are filled with air. In the light of the above statements, choose the most appropriate answer from the options given below
• Both A and R are correct and R is the correct explanation of A
• Both A and R are correct but R is NOT the correct explanation of A
• A is correct but R is not correct
• A is not correct but R is correct

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Important groundwater zones:
• Zone of Aeration:
• Contains air and water
• Includes soil water belt, intermediate belt and capillary fringe
• Zone of Saturation:
• All pores filled with water
• Lies below water table Memory Trick: \[ \boxed{ \text{“Aeration has air, saturation has water”} } \]

Answer 1

The Correct Option is C

Concept: Groundwater hydrology divides subsurface water into different zones depending upon the presence of water and air in soil pores. Broadly, the underground region is divided into:
• Zone of aeration (Vadose zone)
• Zone of saturation Understanding these zones is extremely important in:
• Groundwater movement
• Soil moisture studies
• Well hydraulics
• Irrigation engineering
• Geotechnical engineering The behavior of water and air in pores determines whether the soil belongs to the aeration zone or saturation zone. Zone of Aeration (Vadose Zone): The zone of aeration lies above the groundwater table. In this zone:
• Soil pores contain both air and water
• Water does not completely fill pore spaces The zone of aeration is further subdivided into:
• Soil water belt
• Intermediate belt
• Capillary fringe Zone of Saturation: The zone below the water table where all pores are completely filled with water is called the zone of saturation. In this zone:
• Both micropores and macropores are filled with water
• Air is essentially absent

Step 1: Analyzing Assertion A carefully. Assertion A states: \[ \text{“The zone of aeration consists of soil water belt, intermediate belt and capillary fringe.”} \] This statement is absolutely correct. The standard subdivisions of the vadose zone are:
• Soil water zone or belt
• Intermediate vadose belt
• Capillary fringe Hence: \[ \boxed{\text{Assertion A is correct}} \]

Step 2: Analyzing Reason R carefully. Reason R states: \[ \text{“In the zone of saturation all the macropores are filled with air.”} \] This statement is incorrect. In the zone of saturation:
• All pores are filled with water
• Air is absent Therefore the correct statement should be: \[ \text{“All pores are filled with water.”} \] not air. Hence: \[ \boxed{\text{Reason R is incorrect}} \]

Step 3: Selecting the appropriate option. From analysis:
• Assertion A is correct
• Reason R is incorrect Therefore the correct option becomes: \[ \boxed{ (C)\ \text{A is correct but R is not correct} } \] Final Conclusion: The zone of aeration indeed contains:
• Soil water belt
• Intermediate belt
• Capillary fringe But the reason statement is incorrect because the zone of saturation contains water-filled pores, not air-filled pores. Hence: \[ \boxed{(C)} \]