Q ST QUA TAT ALIT US O TY IN OF W N IN WA NDIA ATER A- 2 R ...

CHAPTER VIWater Quality of Rivers in Brahmaputra Basin6.1 Brahmaputra River SystemThe Brahmaputra basin extends over an area of nearly 5, 80,000 sq km andtraverses a distance of about 2900 km through Tibet (China), India andBangladesh. In India, the basin lies in the states of Arunachal Pradesh, Assam,Nagaland, Meghalaya and West Bengal. The river rises in the Great glacier in thenorthern-most chain of the Himalayas in the Kailash range at an elevation ofabout 5,510 m. It enters India across the Sadiya frontiers tract, west of Sadiyatown into the Assam valley. Here it is joined by two more tributaries viz. theDibang or Sikang and the Lohit, from here onwards the river is known as theBrahmaputra. The river then descends down into the Assam valley from east towest for a distance of about 720 km with its channels meandering from side toside and forming several islands, one of these islands, Majuli covers an area of1,250 sq. Km. during its course the river receives many more tributaries bothfrom the north and the south while some of them are trans-Himalayan rivers withconsiderable discharges.The Brahmaputra has the highest discharge of all the rivers, in India, because ofheavy annual average rainfall in the catchment area. The river has eightsignificant tributaries in India, three from the north are the Manas, the Kameng(or the Jia Bharali) and the Subansiri and three from the east are the Dibang orSikang, the lohit and the Buri Dihing and two from the North West are the Tistaand the Jaldhaka.The basin area of Brahmaputra is covering the States of Arunachal Pradesh,Assam, Nagaland, Meghalaya, Sikkim and West Bengal. The important urbancentres in these States are Shillong (Meghalaya), Guwahati, Jorhat, Dilbrugarh,Siliguri, Alipurduar, Dhubri, Nagaon, Tezpur, Tinsukia (Assam), Dimapur(Nagaland), Kohima (Sikkim), Darjeeling, Dabgram Jalpaiguri, Koch-Bihar(West Bengal).6.1.1 Water Quality Monitoring in Brahmaputra BasinThe State Pollution Control Boards of Assam, Nagaland and Sikkim are doing thewater quality monitoring of the River Brahmaputra and its several tributaries inthe basin. The tributary streams covered under the monitoring programme areBurhidihing, Dhansiri, Disang, Jhanji, Subansiri, Bhogdoi, Bharalu, Borak,Deepar Bill, Digboi, Mora Bharali, Teesta, Dickhu, Maney Khola, Ranichu,Rangit, Jai Bharali, Kathakal, Kharsang, Kolong, Manas, Pagldia, Chathe, Dzu,Kapili, Beki, Kundli, Kushiara, Panchnai, Sankosh, Sonai, Kohara, Ranga,Boginadi, Dikhow, Kaljani, Karola, Dzudza, Dzucha, Dzuna, Sano and Milak.The ranges of water quality observed in the mainstream and tributaries with77