The wide and scenic valley of Bumthang is home to some of the kingdom’s most ancient and precious sites with two major river draining through the valley. The Chamkhar Chhu and the Tang Chhu are the two main rivers of Bumthang, which drains the east of Black Mountain watershed. These rivers are originated from near Gangkhar Puensum (7564m) along with collection of several hill streams. The Chamkhar and Tang Chhu River is possibly for all year-round but the best months we recommend is March, April, November and December. In Winter the water levels decreases because of lowest of winter temperatures traditionally occurs in this region and in Summer though the water level increases because of monsoon rain its of high risk.