The Eleshnitsa springs at an altitude of 2,173 m above sea level from the Osogovo mountain range, 400 meters southwest of the peak Ruen (2,251 m), the highest summit of the mountain range.
In its entirety, the river flows in a deep, weakly afforested valley. In its first 17 kilometers of riverbank, it flows parallel to the border with North Macedonia. Thereafter, it takes a turn northeast until Vaksevo village, then it turns north, and after Chetirtsi village takes a sharp turn east, and after 2 kilometers flows into the Struma at 437 meters above sea level. The river often floods during its peak water levels.[2]
The river basin has a total area of 358 km2 which is 2,07% of Struma's basin.[1][3]
Fish species can be met like Salmo macedonicus, Squalius orpheus, Phoxinus phoxinus, Alburnoides strumicae, Alburnus alburnus, Chondrostoma vardarense, Gobio bulgaricus, Barbus Cyclolepis, Barbatula bureschi, Cobitis strumicae.[4]
Eleshnitsa river receives the majority of its water due to rain-snow feeding and reaches its maximum during April. The minimum amount of water in the river is reached in August. Eleshnitsa is the most turbid river in Bulgaria.[1]
