The Tarnak River is located in Ghazni, Zabul, and Kandahar provinces of Afghanistan. The city of Kandahar is located on a plain directly adjacent to the Tarnak. It rises in Afghanistan's highlands region of Hazarajat, near 33.11667°N, 67.93333°W, south of the Lomar Pass. The Tarnak flows in a south-westerly direction for around 350 km before joining the Dori River some 30 km downstream of the Dori-Arghastan confluence, and some 30 km upstream of the Dori-Arghandab confluence, at 31.4°N, 65.55°W. The combined waters of these rivers join the Helmand at 31.45°N, 64.38333°W, near Lashkargah.

Geography

The Tarnak River valley is a tectonic trough that runs from northeast to southwest. It has multilayered aquifers and both Quaternary and Neocene deposits.