Environmental Geology of the Ganga River Basin

The lithology of the Ganga basin especially the carbonates of the recent alluvium, controls the river water chemistry. Illites and kaolinite are the dominant clay minerals in the suspended sediments. The average TOS is 171 ppm and essentially reflects the Indian river-water average.

Considering the sediment transport at Farakka (744 million tonnes/yr) as a measure, the Ganga is placed as the third largest sediment transporting river of the world after the Yellow and Amazon rivers. Basin area and discharge, rather than the basin elevation, control the erosion rate. The total erosion rate (549 t/km²/yr) of the basin at Calcutta is almost three times that of Amazon and three and half times that of the world average (150 t/km²/yr).

The high sedimentation fate (42 mm/yr) in the Yamuna around Delhi is mainly due to the solid waste supply from urban areas. For selective heavy metals, the total drain anthropogenic contribution to the river Yamuna is Mn (42%), Fe (76%), Cu (62%), Zn (90%) and Pb (50%) of the metal increase in the sediments from Wazirabad to Okhla. Excellent correlation among Cu, Zn and Pb in the core and in surface sediments indicates their common source. The additional metals carried into the surface and core sediments of the Yamuna due to increased human utilization of the river basin are in relatively mobile fractions of the sediments and hence pose clear environmental hazards.