Which of the following is/are the possible consequence/s of heavy sand mining in riverbeds ? 1. Decreased salinity in the river 2. Pollution of groundwater 3. Lowering of the water-table Select the correct answer using the code given below :
- (a) 1 only
- (b) 2 and 3 only ✓ UPSC's answer
- (c) 1 and 3 only
- (d) 1, 2 and 3
Why the answer is (b)
• Riverbed sand acts as a natural aquifer and filter; removing it deepens the channel and cuts off recharge, so the water table in adjoining areas falls (3).
• Loss of the sand filter and exposure of the aquifer let pollutants enter groundwater (2); in coastal rivers it also allows seawater intrusion, increasing — not decreasing — salinity, so (1) is wrong.
• Sand mining also erodes banks and damages bridges and aquatic habitats; the Supreme Court and NGT have restricted it.
• Hence 2 and 3 only, option (b).
Why the other options are wrong
- (a) 1 only
- Salinity tends to increase, not decrease.
- (c) 1 and 3 only
- Statement 1 is wrong; groundwater pollution (2) is a real consequence.
- (d) 1, 2 and 3
- Statement 1 is wrong.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2018, held on 3 June 2018. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.