ECOSYSTEM STUDIES ON UPPER REGION OF GANGA RIVER, INDIA

A multi-disciplinary research programme on the Ganga River Ecosystem w as launched by the Government of India in 1983 to collect information on its attributes. Monitoring of the initial 509 km unpolluted and unm onitored region of the river falling in partly mountainous and partly upper plain stretches for two years revealed good water quality. The S ong River (a tributary) catchment, a victim of extensive mining activi ty in the past, was found to add maximum mineral load. The Bhagirathi River was found to carry maximum suspended solid load. Organic polluti on was low throughout, occasionally showing seasonal and local peaks. The river exhibited a high oxidative state with pH falling in a slight ly alkaline range and nutrient levels being very low. Diatoms formed a major part of the encountered genera of phytoplankton. Zooplankton we re mainly represented by protozoans. Saprophytic bacteria underwent la rge spatial and temporal fluctuations. Coliforms exhibited an increasi ng trend with downstream river distance. The source of pollution could not be specifically characterized from an FC/FS ratio. Only one sampl e tested positive for enteric virus. The forms of benthic macroinverte brates indicated a clean stream environment. It was observed that dive rsity indices, together with evenness and community comparison, could provide a promising approach to determine the state of the community. Eight heavy metals investigated, Cu, Zn, Fe, Cd, Mn, Pb, Ni and Co, we re found to be present in the river water and bed sediments. The promi nent mode of metal transport was found to be via the suspended load. T he concentration of dissolved metals was found within WHO permissible limits. The heavy metal status of the Ganga River was compared with ot her rivers of the world. Sorptive properties of sediments were found t o be similar to the general sorptive behaviour of the clays. Laborator y studies exhibited reasonable short t(90) values for coliform surviva l in Ganga water. Faecal streptococcus survived longer.