Environmental Impact of Sand Mining

Heavy sand mining in riverbeds has several documented environmental consequences. Sand mining lowers the water table as it removes the upper permeable layers that facilitate water infiltration and storage, so statement 3 is correct. Sand mining also exposes underground water reserves to direct contamination from surface pollutants, leading to groundwater pollution, making statement 2 correct. However, statement 1 is incorrect because salinity in rivers is determined by dissolved minerals and salt content, not by sand removal. Sand mining does not decrease salinity; in fact, it may concentrate salts if water levels drop. The correct answer includes statements 2 and 3, which address actual hydrogeological consequences of sand mining.

Answer: (b).