The river takes its source from the Velichka spring at an altitude of 755 m, situated near the second class
II-58 road Asenovgrad–
Kardzhali some 1.5 km west of the Panichkovo resort in the Eastern
Rhodope Mountains. It flows in a deep forested valley until the village of
Boyan Botevo, where it turns southeast and flows through the Haskovo hills in a narrow shallow valley. Downstream of the village of
Malevo the Harmanliyska reka turns in northeastern direction and after
Stoykovo it bends eastwards, bypassing the Huhla ridge from the north in a valley with steep slopes on the right bank and oblique slopes on the left one. It forms a 9–10 gorge before reaching the town of
Harmanli, where the river flows into the
Maritsa at an altitude of 73 m about 1.3 km northeast of the town. Its drainage basin covers a territory of 956 km2 or 1.8% of the Maritsa's total and borders the drainage basins of the
Banska to the north and northwest, the Biserska reka to the southeast and the
Arda to the southwest, all of them right tributaries of the Maritsa. The Harmanliyska reka has predominantly rain–snow feed with high water in February–March and low water in August. The average annual flow near the Harmanli is 5.47 m3/s. The record flow was measured on 12 February 1942 — 708 m3/s. The mineralization of the water is 300–400 mg/dm3. The average annual water temperature of the river at Harmanli reaches 12.3 °C. It freezes for an average of 10 to 20 days a year. == Settlements and economy ==