Environmental Geology of Peninsular River Basins of India

An attempt is made to evaluate the environmental geology of non-Himalayan rivers of India. These twenty river basins including eleven medium basins together drain nearly 25 per cent of the sub-continent. The annual transport of suspended sediments and dissolved salts by these rivers have been estimated to be around 370 million tonnes and 61 million tonnes respectively. The rate of physical erosion among these basins range from 799 tonnes/km²/yr to 16 tonnes/km²/yr. Similarly, chemical erosion ranged from 110 tonnes/km²/yr to 22 tonnes/km²/yr.

Among the rivers considered, the chemical composition of water indicates that Cauvery carries a large silica load (39 ppm), while the TDS is low (172 ppm), whereas Sabarmati has the highest TDS (352 ppm). Krishna waters show the highest alkalinity. In all the rivers, conductivity shows good correlation with TDS. Sediment chemistry indicates that Cauvery river sediments are most siliceous while that of Godavari are least siliceous. In both these cases, average SiO₂ is higher than the Indian average river sediment. Similarly, Fe in southern river sediments is very high while P is very low compared to the Indian or world average. Apparently local geology (Shield area hard rocks in southern India and Deccan Traps in central India) control the water and sediment characteristics of the peninsular rivers.