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.

[1] It rises in Afghanistan's highlands region of Hazarajat, near 33°7′N 67°56′E / 33.117°N 67.933°E / 33.117; 67.933, south of the Lomar Pass.

[2] The combined waters of these rivers join the Helmand at 31°27′N 64°23′E / 31.450°N 64.383°E / 31.450; 64.383, near Lashkargah.

[3] The Tarnak River valley is a tectonic trough that runs from northeast to southwest.