After originating in the Tirth Top, the Tirthan River flows uninterrupted through the core zone of the Great Himalayan National Park, roaring and crashing through the hills, travelling for about 60 kilometers through Rola, Darkhali, Ropa, Gushaini, Khundan Banjar, Mangalore and Balichowki. There is no habitation on either side of Tirthan River until it reaches Gushaini. Later, at a place called Larji, it is met by the Beas River and the Sainz River this confluence of the three rivers is the site of a hydropower project. Through the trajectory of the Tirthan River, there is a treasure trove of very rare medicinal herbs, which give the water its medicinal properties. The entire valley is surrounded by a network of seasonal and perennial tributaries, waterfalls, streams and springs that meet the Tirthan River.