Which of the following is/are the possible consequence/s of heavy sand mining in river beds?1.Decreased salinity in the river2.Pollution of groundwater3.Lowering of the water-tableSelect the correct answer using the code given below:

1. A

   1 only

   (a) 1 only. Heavy sand mining does not characteristically decrease river salinity; in coastal reaches it can worsen saline intrusion. Statement 1 is therefore not a valid consequence. This option is not the key.

2. B

   2 and 3 only

   (b) 2 and 3 only. Removing the sand aquifer’s filter and storage lowers the water-table and can pollute groundwater by exposing it to river contaminants and by damaging the hyporheic buffer. Statements 2 and 3 follow; 1 does not. This option is the official key.

3. C

   1 and 3 only

   (c) 1 and 3 only. Water-table fall (3) is real, but decreased salinity (1) is not the expected effect. This option is not the key.

4. D

   1, 2 and 3

   (d) 1, 2 and 3. Statement 1 is wrong, so the full set fails. This option is not the key.

Summary. Official key is (b) 2 and 3 only. River-bed sand stores and filters water. Mining it lowers the local water-table and can contaminate groundwater. Salinity in the channel is not thereby decreased; coastal mining may even pull the salt wedge inland. Statement 1 therefore drops. The surviving consequences are pollution of groundwater and lowering of the water-table.