Tons River
The Tons is the largest tributary of the Yamuna. It flows through cultural Mahasu region in Uttarakhand and Himachal Pradesh, marking the boundaries of the two states after Tyuni, where confluence of Tons and Pabbar river happen. The Tons thrust is named after this river.
With its source in the high Bandarpunch mountain, it is one of the most major perennial Indian Himalayan rivers. In fact, it carries more water than the Yamuna itself, which it meets below Kalsi near Dehradun, Uttarakhand.
Tons Valley
Tons Valley lies in Jaunsar Bawar region, as it emerges from the Himalayas has haridwar on its eastern bank. The cantonment town of Chakrata is situated between, the Tons and Yamuna rivers.Tributaries
The Pabbar River is a tributary of the Tons River connecting to it from the west. It is also the westernmost river that drains east to the Ganges. The Sutlej River is the next watershed over and is the easternmost river that drains west into the Indus.The Asan River is another tributary of the Tons that is often named after this great river as the Tons. The Asan is a confluence of two small river systems, one comprising streams flowing south from the Himalayan range running from Vikas Nagar towards Tehri, and the other comprising streams flowing north-west from the lower Shiwalik hills. The misnomer Tons stands for the river originating from the Mussorie hills, flowing down through Robber's cave, Bijapur canal and Tapkeshwar Mahadev, before emerging into a broad valley behind IMA. This river receives substantial waters from several streams flowing south from the Himalayan slopes. It goes on west beyond the locality of Premnagar to finally join the streams from the lower Shiwaliks and flow toward the Yamuna, which it joins near Poanta Sahib. Asan barrage is constructed just before this confluence.