Context: According to the Karnataka State Pollution Control Board (KSPCB), the strict enforcement of 21-day lockdown due to the COVID-19 pandemic has reduced the pollution in Kaveri river and its tributaries.

• According to the Karnataka State Pollution Control Board (KSPCB), the Cauvery and tributaries like Kabini, Hemavati, Shimsha, and Lakshmana Tirtha are regaining their decades-old status in terms of water quality.
• Also the untreated sewage from residential areas, pollutants from industries, religious waste material from pilgrims, and construction debris had been polluting the rivers.
• These rivers were flowing with hazardous elements such as lead, fluoride, faecal coliform, and some suspended solids in highly dangerous quantities. 
• It is evident that the lockdown has significantly brought down the pollution level in rivers, said sources in KSPCB.
• However, the board will test the water samples at the regional laboratory in Mysuru under the national programme Monitoring of Indian National Aquatic Resources and Global Environmental Monitoring Scheme.

About Global Environment Monitoring System (GEMS)

• It was introduced in 1975 at the United Nations Conference on the Human Environment.
• It is a global operation that collects information to better understand and protect the Earth’s environment.
• This effort is made with the cooperation of other countries, who contribute data to the GEMS.

About Monitoring of Indian National Aquatic Resources (MINARS)

• It is a National Programme of monitoring national aquatic resources.
• It was started in 1984, with a total of 113 stations spread over 10 river basins.
• The present network comprises 870 stations on rivers, lentic water bodies and subsurface waters.

About Cauvery River

• It also Known as Dakshina Ganga or the Ganga of the South.
• It rises at an elevation of 1,341 m at Talakaveri on the Brahmagiri range near Cherangala village of Kodagu (Coorg) district of Karnataka.
• The total length of the river from origin to outfall is 800 km.
• The Cauvery basin extends over states of Tamil Nadu, Karnataka, Kerala and Union Territory of Puducherry draining an area of 81 thousand Sq.km.
• It is bounded by the Western Ghats on the west, by the Eastern Ghats on the east and the south and by the ridges separating it from Krishna basin and Pennar basin on the north.
• The Nilgiris divide the basin into two natural and political regions i.e., Karnataka plateau in the North and the Tamil Nadu plateau in the South.

Tributaries of the Cauvery River

• Left Bank: the Harangi, the Hemavati, the Shimsha and the Arkavati.
• Right Bank: Lakshmantirtha, the Kabbani, the Suvarnavathi, the Bhavani, the Noyil and the Amaravati joins from right.