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
Reasons (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

Correct option is A

Large dams regulate the flow of rivers by controlling floods and storing water for various purposes, such as irrigation and hydroelectric power generation. However, by doing so, they reduce the natural deposition of nutrient-rich sediments (silt) on floodplains during seasonal floods. These sediments are crucial for maintaining soil fertility. Without regular silt deposition, floodplains become less fertile over time, leading to a decline in agricultural productivity.
Thus, Assertion (A) is correct.
Dams trap sediments, including silt, in their reservoirs. As a result, downstream areas, including floodplains, receive significantly less sediment deposition. This directly impacts the natural replenishment of nutrients in the soil of floodplain areas.
Therefore, Reason (R) is also correct and provides the logical explanation for the assertion.
Information Booster: · Floodplain Agriculture: Floodplains are traditionally fertile because they receive annual deposits of silt carried by river floods.
· Impact of Dams: By trapping silt, dams reduce soil fertility downstream, disrupt aquatic ecosystems, and affect agriculture-dependent communities.
· Examples: The Aswan High Dam on the Nile River has reduced the fertility of Egypt’s floodplains, leading to increased reliance on artificial fertilizers.