Eco. Env. & Cons. 29 (November Suppl. Issue) : 2023; pp. (S54-S58) Copyright@ EM International ISSN 0971–765X Classification of Rivers of Brahmaputra Basin in Assam, India Based on Designated Best Use Concept Rekha Bora, Lalit Saikia*, Larihun Jeengaph and Rupjyoti Payeng Department of Earth Science, University of Science and Technology Meghalaya, 9 th Mile, Meghalaya 793 101, India (Received 25 May, 2023; Accepted 2 July, 2023) ABSTRACT River water quality is an important issue as rivers are one of the major sources of fresh water for drinking, agriculture, residential use, hydroelectric power plant, tourism, transportation, and others. In spite of abundance of surface water in Brahmaputra basin, only 47% rural population of Assam has access to potable water. It is important to check water quality at regular intervals and prevent and control their pollution. An attempt was made to study water quality of rivers of the Brahmaputra basin in Assam focusing designated best use concept. Water quality status was evaluated from analysis of water samples and secondary data from reports of Central Water Commission and Pollution Control Board, Assam. It is found that water of most of the rivers fall under ‘B’ and ‘C’ class (as per designated best use concept, class ‘B’ water can be used for bathing and class ‘C’ water can be used as drinking water source with conventional treatment followed by disinfection). Most of the rivers of the Brahmaputra basin have moderate or low pollution, mainly due to rejuvenated life every year during monsoon. However, with contemporary issues of population explosion, increasing demand for water, flood, growing pollution and climate change, it is imperative to take precautionary approach to the pristine as well as ecologically challenged rivers of Brahmaputra basin in India. Key words: Brahmaputra basin, Assam, Water quality, Designated best use concept Introduction The Brahmaputra River basin occupies 30% of the country’s total water resources and are the highest among all the river basins in the Indian subconti- nent. The Brahmaputra along with the well-knit net- work of its tributaries controls the geomorphic re- gime of the entire region of the Brahmaputra valley (Mahanta and Saikia, 2015). The major rivers are mostly precipitation dominated during monsoon season and many are snow fed type during the lean flow period. In spite abundance of surface water, according to a UNICEF report, only 47% rural popu- lation of Assam has access to potable water. Due to contamination of ground water by arsenic, fluoride and iron, surface water sources, i.e., rivers are suit- able options as drinking water sources. It is neces- sary to monitor water quality of rivers to prevent and control pollution. Water quality of the Brahmaputra River in Assam have been extensively studied by many researchers (Dutta et al., 2020; Barbulescu et al., 2021). Multivari- ate statistical techniques were used in Jia Bharali river study for analysis and interpretation of com- plex datasets, and in water quality assessment, iden- tification of pollution sources/factors and under- standing temporal/spatial variations in water qual- ity for effective water quality management (Khound and Bhattacharya, 2017). The overall index of pollu- tion in Jia Bharali river was found to be 0.14 to 1.21 DOI No.: http://doi.org/10.53550/EEC.2023.v29i06s.008