The Narmada River is the largest westward-flowing river of peninsular India. It is a rain-fed river and carries an annual mean discharge of about 36 million acre-feet (MAF) (about 45 billion cubic meters). Through most of its total course of 800 miles, it traverses between the mountain ranges of Vindhyachal in the north and Satpuda in the south before it enters the plains of the state of Gujarat to run its final 100 miles. Because of such a difficult and varied terrain, the river remains one of the least developed rivers of India. In the hills of the these ranges live tribal people. They are mainly of three types—Bhils (Vasavas), Rathwas (Bhilalas, Pavras), and Tadvis.