Given below are two statements: one is labelled as Assertion A and the other…
2022
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion (A): Large dams on rivers tend to reduce the fertility of land areas in the river flood plain.
Reason (R): Dams reduce the deposition of silt over land areas in the river flood plain.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer: A. Both (A) and (R) are correct and R is the correct explanation of A — ConceptRiver floodplains are naturally fertilized when floods spread fine, nutrient-bearing sediment over the land. A dam interrupts this sediment-transfer…
- 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
Show answer & explanation
Correct answer: A
Concept
River floodplains are naturally fertilized when floods spread fine, nutrient-bearing sediment over the land. A dam interrupts this sediment-transfer system because much of the river load settles in the reservoir instead of moving downstream.
Application
Large dams slow the river at the reservoir, so suspended silt is deposited there.
Downstream floods therefore carry and deposit less nutrient-rich silt on the floodplain.
With less periodic replenishment of mineral and organic matter, floodplain soil can lose fertility over time. Thus, both Assertion (A) and Reason (R) are correct, and (R) correctly explains (A).
Cross-check / Contrast
“Both are correct but not causally related” misses the sediment-to-soil-fertility link.
“A is correct but R is not” conflicts with sediment trapping by reservoirs.
“A is not correct but R is correct” ignores the role of fresh silt in renewing floodplain soil.