Assertion–Reason (North Indian rivers flood in summer)\nAssertion (A): Most rivers in the North Indian plains experience flooding during the summer season.\nReason (R1): Many rivers originate in the Himalayas and are fed by melting snow.\nReason (R2): The rivers are also fed by monsoon rains during the summer months.\nIdentify which reason(s) truly explain A.

Difficulty: Easy

Correct Answer: If both (R1) and (R2) are reasons for the assertion (A).

Explanation:


Introduction / Context:
Flood seasonality in North Indian plains reflects dual inputs: Himalayan snowmelt and monsoon rainfall. The item asks if both reasons explain observed summer flooding.



Given Data / Assumptions:


  • A: Summer flooding is common.
  • R1: Snowmelt augments discharge from Himalayan catchments.
  • R2: Monsoon rains peak in summer, further increasing flows.


Concept / Approach:
Hydrographs in snow–monsoon regimes show combined contributions. When both inputs overlap temporally, peak flows and flood probability rise.



Step-by-Step Solution:


1) R1 adds sustained baseflow and diurnal melt pulses.2) R2 adds intense rainfall-runoff, sometimes overwhelming river capacity.3) Superposition of inputs explains seasonal floods—thus both reasons are valid.


Verification / Alternative check:
Historical flood records align with monsoon onset and elevated melt periods.



Why Other Options Are Wrong:
A/B understate the dual-driver nature; D contradicts hydrology.



Common Pitfalls:
Treating snowmelt and monsoon as mutually exclusive.



Final Answer:
If both (R1) and (R2) are reasons for the assertion (A).

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