Arghandab River
Arghandab is a river in Afghanistan, about in length. It rises in the Hazarajat country north-west of Ghazni, flows south-west passing near the city of Kandahar, and then falls into the Helmand below Girishk. In its lower course it is much used for irrigation, under the control of the Helmand and Arghandab Valley Authority, and the valley is cultivated and populous; yet the water is said to be somewhat brackish. It is doubtful whether the ancient Arachotus is to be identified with the Arghandab or with its chief confluent the Tarnak, which joins it on the  left southwest of Kandahar. The Tarnak, which flows south of Kandahar, is much shorter (length about 320 km or 200 miles) and less copious. Historical background. The river was known to the ancient Iranians as "Haraxvaiti" in Avestan and "Harahuvati" in Old Persian, which are cognate with Rigvedic "Sarasvati" (as described in its "family books"). Scholars such as Boyce and Parpola have identifed Greek "Arachosia" as a hellenisation of the name, meaning the land of "Haraxvaiti". Rigveda's hymn VI.61.2 describes it with the words: Historian Asko Parpola states: "Arghandab [...] descends from a height of nearly four kilometers down to  about 700 meters when it joins the Helmand River, which eventually forms shallow lakes." "Sarasvatī-" is interpreted to mean "full of lakes". Some historians, however, assert that the Avestan "Haraxvaiti" as well as the Rigvedic "Sarasvati" refer to the Helmand River. The Rigvedic name of Arghandab is then believed to be Drishadvati. The ruins at Ulan Robat, supposed to represent the city Arachosia, are in its basin; and the lake known as Ab-i Istada, the most probable representative of Lake Arachotus, is near the head of the Tarnak, though not communicating with it. The Tarnak is dammed for irrigation  at intervals, and in the hot season almost dries up. Upper course. The upper course of the Arghandab river is relatively unexplored. The "Historical and Political Gazetteer of Afghanistan" cites the explorations of Major G. Lynch in 1841, according to whom the origin of the Arghandab is 20 to 30 miles north of Sang-e-Masha. This places the source in the mountains southwest of the Nawar basin. Lynch also described the upper course of the river as being a "mountain torrent, dashing over great granite rocks and about 3 feet deep where fordable". Lower course. There is a good  deal of cultivation along the river, but few villages. The Kabul-Kandahar Highway passes this way (another reason for supposing the Tarnak to be Arachotus), and the people live off the road to avoid the onerous duties of hospitality. Dahla dam. In 2008 a project was initiated to rehabilitate the Dahla Dam and associated irrigation system.