This river originates from the Jamnotri mountain in the Himalayas at a height of about 7,924 m from the mean sea level. After crossing through Garhwal and irrigating Jaunsar area, it flows on the eastern boundary of the district for a distance of about 22 km. Entering at village Khodar Majri and leaving at Kaunch and continues in the Uttar Pradesh. It separates Kayarda Dun from the Dehradun and forms the boundary line between this district and the Utter Pradesh. Within the boundary of this district the estimated maximum width of the river is bout 91m and the depth about 6m but this limit is far exceeded during the rainy season. In the summer, due to melting of snow on the mountains, the volume of water of the river is often subject to variation because of which the Canal Department has installed at Paonta, an instrument for taking measurements of the water, and has also established an office, equipped with a telephone, for giving timely information, about the variation of the volume of water to the Canal Office, situated at Dadupur. The water of this river is generally cold and clear but during the summer, due to melting of snow, it becomes somewhat muddy. It is a sacred river having two temples on its bank, at Rampur and at Paonta where a Gurudwara also exists. Since this river flows at a lower level than of the plateau of the Kayarda Dun, its water cannot be made use of for irrigating the area. The timber which comes from the mountains through the Tons and the Giri rivers is caught at Rampur Ghat and taken down floating to the plains.
It notable tributaries in the district, are the Tons meeting it at Khodari Majri, the Giri Joining it near Rampur Ghat and the Bata mingling its water with it at Bata Mandi.
By far the greater portion of the district is drained by the Giir or its tributaries. It takes its rise in the hills of Jubbal and courses through the hills of Kot-Khai and Tatesh, parts of Shimla district, and enters in the district on its south-west side. It continues its course for about forty kilometers forming the boundary with the Keonthal area of the Shimla district. At village Mandoplasa, this district and debouches in the Yamuna at Rampur Ghat.
The Rampur Giri canal has been constructed which takes off this river near Mohkampur Nawada. There is a ferry on this river at Shayampur. A variety of fish is found, more particularly, Mahseer. Timber, in considerable quantities, is floated down this river into the Yamuna and at some places irrigation is also done.
None of its tributaries are important, except, on its right bank, the Jalal, which joins it at Dadahu below Sati Bagh at the south-eastern extremity of the Sain Dhar. On its left bank the principal streams are the Nait and Palar, which rise on the Kawal, a stream which first flows westward, till it falls into the Giri. Lesser tributaries are the Bajhethy, the Pervi, the Khal and the Joggar streams.
The source of this river lies in the Jamnotri mountains and after coursing through the territories of Jubbal and Jaunsar it enters the district near village Kot separating it from the Jannsar area, once a part of the erstwhile princely state of Sirmour. After flowing for about 50km and forming the eastern boundary of the district it joins the Yamuna near Khodar Majri, too soon losing its name in that of the Yamuna, which is trebled in size after the junction of the two rivers. When it issues from its bed of snow at an elevation of about 3,897 m. above the level of the sea, it flows in a grand volume, 9m wide and 9m deep maintaining its dignity of character until its confluence with the river, which should, if rivers had their just rights, have been considered its tributary. During its comparatively short career, the Tons receives into its bosom the water of several other beautiful streams. The current of this river is swift and the course full of stones.
This small, shallow and narrow river rises near village Bani below Nehi in tehsil Pachhad and forms a dividing line between the Sain and the Dharthi. At Dadahu in SubTehsil, it falls into the Giri river losing its name. It is generally fordable and rarely up-passable except when it flood which passes away soon.
It rises at Baraban in the hills of Katasan and pass below a temple of Katasan Devi. After flowing from south-east to south-west for a distance of about 24 km. With in the district, irrigating Bajora area, it passes on to the Ambala district at Kala Amb where it is quite wide at village Dewani it is joined by a streamlet named Salani. Areas of Bajora, Kala Amb the lands of Shambhuwala, Rukhri and the garden of Bir Bikrambag and the Khadar Bag are irrigated by its water and few water mills are also run. Its only tributary, of any importance, is the Salani.
This river issues from Siori spring in the Dharthi range, located in village Bagna tehsil Nahan and takes easterly direction reverse to the course of the Markanda. Dividing Kayarda Dun into two parts it joins Yamuna at Bata Mandi and loses its separate entity and name. Dun area is irrigated by its water. It is a perennial stream subject to heavy floods in the rainy season, though usually for badable.