The river Bharalu and Kolong are among the 71 most polluted stretch of river in the country, according to a study by the Central Pollution Control Board (CPCB).
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/bharalu-kolong-among-71-most-polluted-rivers
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/assam-tribune
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/kolong
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/national-river-conservation-directorate
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/assam
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/meghalaya
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nagaland
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sikkim