The Siswa is a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

and valley in the

Sankhuwasawa District Sankhuwasabha District ( ne, सङ्खुवासभा जिल्ला ) is one of 14 districts of Province No. 1 of eastern Nepal. The district's area is 3,480 km2 with a population of 159,203 in 2001 and 158,742 in 2011. ...

. It is a tributary of the Arun.

References

Rivers of Koshi Province {{Nepal-river-stub