The Central Pollution Control Board (CPCB) in association with State Pollution Control Boards, monitors the water quality of rivers.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/rs-5800-crores-released-cleaning-34-polluted-rivers-government
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/asian-age-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rivers
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution