Explanation:

The Ganga is India’s longest river (2,525 km) and is considered the holiest of rivers by Hindus. It was declared a national river by Prime Minister Manmohan Singh in 2008 in order to achieve the objectives of the Ganga Action Plan, initiated by PM Rajiv Gandhi in 1985. The Plan, a clean-up operation, had focussed on municipal sewage. Under Singh’s tenure, the Ganga River Basin Authority was set up to broaden the clean-up operation, integrate pollution control, sustainable use of water and flood management.