UPSC Prelims 2018 Q81: Environment & Ecology – Water & Wetland Conservation
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (b) 2 and 3 only
Explanation
Heavy Sand Mining in Riverbeds - Consequences
| Consequence | Occurs? | Detail | Detail |
|---|---|---|---|
| 1 | Decreased salinity in the river | NO | Heavy sand mining often INCREASES salinity, especially in coastal river stretches, because deepening the channel allows seawater intrusion. Sand mining does NOT reduce salinity. |
| 2 | Pollution of groundwater | YES | Sand mining exposes aquifers, allowing pollutants (heavy metals, effluents, sewage) to seep directly into groundwater, contaminating drinking water sources. |
| 3 | Lowering of the water table | YES | Removing sand disrupts the natural filter that recharges aquifers - the water table drops as recharge fails and evaporation increases from exposed water. |
Answer: (b) 2 and 3 only.
Why each option is right or wrong
- (a) Incorrect. Statement 1 is wrong - sand mining does not decrease salinity; it often increases it via seawater intrusion.
- (b) CORRECT. Groundwater pollution (2) and lowering of the water table (3) are established consequences of heavy sand mining.
- (c) Incorrect. Statement 1 (decreased salinity) is not a correct consequence.
- (d) Incorrect. Salinity typically increases (not decreases) with heavy sand mining.
Key point
Sand mining harms: Riverbed lowering, bank erosion, aquifer exposure, groundwater pollution, water table decline, saltwater intrusion (near coast), habitat destruction, changes in flow hydrodynamics. National Sand Mining Framework 2018 and NGT orders regulate it.
Remember
Heavy sand mining in riverbeds causes pollution of groundwater by exposing aquifers to surface contaminants and lowers the water table by disrupting the natural sand-filter aquifer recharge mechanism. It does NOT decrease salinity - if anything, it can INCREASE salinity in tidal river stretches by enabling seawater intrusion into the deepened channel.
Common mistakes
- Assuming any river disturbance dilutes salinity - actually deepening the channel enables seawater intrusion, INCREASING salinity in tidal zones.
- Overlooking the water-table impact - sand acts as a natural aquifer recharge medium; removing it starves aquifers.
- Missing that groundwater pollution is a critical impact - exposed aquifers are directly contaminated by surface effluents.
Exam tip
Sand mining regulation in India: Environment (Protection) Act 1986, EIA Notification 2006, NGT orders (Deepak Kumar 2012), National Sand Mining Framework 2018 by MoEFCC. State-level District Survey Reports mandatory.
Sources
- MoEFCC - National Sand Mining Framework (2018)
- CPCB - Guidelines on Environmental Aspects of River Sand Mining