Yamuna

The only river in Himachal belonging to the Ganga system — the other four are Indus-system rivers. It never really flows through the state so much as along it, forming the eastern boundary with Uttarakhand through Sirmaur.

Its tributaries matter more here than the river itself. The Tons is the largest tributary of the Yamuna anywhere and carries more water than the parent stream where they meet; the Giri divides Sirmaur into Cis-Giri and Trans-Giri, the second of which is the Hatti homeland.