A multipurpose project is that type of project which fulfills a variety of purposes at the same time, for example, irrigation, generation of electricity, flood control, fish breeding, etc.
Kaveri, Mahanadi, and Narmada lie within the Indian borders throughout their course ensuring a greater authority in initiating those very expensive multipurpose projects. In the case of Brahmaputra, its upper stage(rapid speed) and most of the middle stage lies in China. This part of the course of the river is ideally suited for multipurpose projects. When it comes to India, it loses its speed and energy, carries lots of water and suited for navigation and irrigation only and not for something as big as a Multipurpose Project.