Which of the following is/are the possible consequence/s of heavy sand mining in river beds? 1. Decreased salinity in the river 2. Pollution of groundwater

1. A. 1 only
2. B. 2 and 3 only
3. C. 1 and 3 only
4. D. 1, 2 and 3

Answer: B

Explanation

Excessive instream sand-and-gravel mining causes the degradation of rivers. Instream mining lowers the stream bottom, which may lead to bank erosion. Depletion of sand in the streambed and along coastal areas causes the deepening of rivers and estuaries, and the enlargement of river mouths and coastal inlets. It may also lead to saline-water intrusion from the nearby sea. The effect of mining is compounded by the effect of sea level rise. Any volume of sand exported from streambeds and coastal areas is a loss to the system. Excessive instream sand mining is a threat to bridges, river banks and nearby structures. Sand mining also affects the adjoining groundwater system and the uses that local people make of the river. Sand aquifer helps in recharging the water table and sand mining causes sinking of water tables in the nearby areas, drops leaving the drinking water wells on the embankments of these rivers dry. Turbidity increases at the mining site.