When was Namami Gange Programme launched to clean the Ganga river?

The correct answer is 2014.

Explanation:
The Namami Gange Programme is an Integrated Conservation Mission, approved as a 'Flagship Programme' by the Union Government of India in June 2014 with a budget outlay of ₹20,000 Crore to accomplish the twin objectives of effective abatement of pollution, conservation and rejuvenation of the National River Ganga.

Key details of the programme include:
1. It is implemented by the National Mission for Clean Ganga (NMCG) and its state counterpart organizations.
2. Its main pillars involve sewage treatment infrastructure, river-front development, river-surface cleaning, biodiversity conservation, afforestation, and public awareness.