It enters Himachal Pradesh at ‘Khadar Majri’ in Sirmaur district. Yamuna river is the largest tributary of the Ganga. The Yamuna has mythical relation to the Sun. it rises from ‘Yamunotri’ in Garhwal hills and forms the Eastern boundary with Uttarakhand. The Yamuna is the Eastern – most river of Himachal Pradesh. Its famous tributaries are Tons, Pabbar and Giri or Giri Ganga. The Giri Ganga rises from near ‘Kupar peak’ just above Jubbal town in Shimla district, Tons from Yamunotri and Pabbar from Chandro Nahan Lake near the ‘Chanshal peak’ in Rohru tehsil of Shimla district. Its total catchment area in Himachal is 2,320 square km. It leaves the state near ‘Tajewala’ and enters into the Haryana state. It flows nearly 22 km. in Himachal Pradesh.
Jalal River : Jalal is the small tributary of the Giri river in Himachal Pradesh. It rises from ‘Dharthi ranges’ adjoining Pacchad and joins Yamuna at ‘Dadahu’ from the right side. It also joins the river Giriganga at Dadahu. The origin and entire course of this river lies in the lower Himalayas. This is the rainfed river and has abrupt flow during the rainy season. A numner of human settlements have come up along with Jalala river. These include Bagthan and Dadhau.
Markanda River : Markanda is a small river of Nahan area of the Sirmaur district. It rises from the Southern face of the lower Himalayas on the Western extremity of the Kiarda dun (Panota) valley. The lower Himalayan hills of Nahan occur on the right flank of the Markanda valley while the low rolling Shivalik hills are on its left flank. It is a rainfed river and has very low flow in the winter and summer months, but rises abruptly in the monsoon.
Andhra River : This is a tributary of the Pabbar River which in turn drains into the Tons river. This river rises from a small glacier tenated in a cirque of the lower hills of the main Himalayas in the area to the North West of Chirgaon in Shimla district. Thereafter it flows in a general direction towards South – East and merges with the Pabbar river at Chirgaon.
Giri River : The river Giri is an important tributary of the Yamuna. It drains a part of South – Eastern Himachal Pradesh. The Giri or Giriganga as it is famous in the Jubbal, Rohru hills that rises from ‘Kupar peak’ just above Jubbal town after flowing through the heart of Shimla hills flown down in the South – Eastern direction and divides the Sirmaur district into two equal parts that are known as Cis – Giri and Trans – Giri region and joins Yamuna upstream of Paonta below Mokkampur.
Asni River : The Asni river is a tributary of the Giri river which in turn drains into the Yamuna river. This river flows along a deep V shaped valley whose side shopes vary from steep to precipitous. It has carved a steep gorge across the offshoots of the Nag Tibba ridge. Numerous small springs fed tributaries join the Asni river at various places along its course.
Bata River : The river originates in the boulders below the ‘Nahan ridge’ in the South – Western corner of Himachal Pradesh as the Jalmusa – ka – Khala. It is mainly fed by rain water that is cycled as underground water before finally coming up on the surface as a spring. The river flows below the surface for a part of its length in its upper reaches, thereafter the water flows on the surface. Large and wide terraces have been formed by it.
Pabbar River : The Pabbar is a tributary of thee Tons river, which in turn drains into the river Yamuna. This rises from the Dhauladhar range (South facing slopes) near the border of UP and Himachal Pradesh and the extreme North – Eastern of Shimla district. The main stream is fed by the Chandra Nahan glacier and springs originating from underground waters. It joins the Tons river at the base of the Chakrata massif near the border of Uttrakhand and Himachal Pradesh.
Patsari River : The Patsari is a small spring fed tributary of the Pabbar river. This river rises from the lower Himalayan hills near Kharapathar in Shimla district of Himachal Pradesh. This river joins the Pabbar river near the mountain hamlet of Patsari about 10 kms upstream of Rohru. Its bed is strewn with boulders of various sizes. Small villages and hamlets have come up along the Patsari rivers.
Tons River : This river is an important tributary of the Yamuna river and join it at ‘Kalsi in the North – Western part of Dehradun valley (approximately 48 km. away from Dehradun.) It rises as the following two feeder streams – the Supin river rises in the Northern part of the Tons catchment near the Himachal Pradesh and Uttrakhand border – the Rupin river rises from a glacier at the head of the famous Har – Ki – Dun valley in the North – North Eastern part of the Tons catchment.