From Wikipedia - Reading time: 4 min
| Oleška | |
|---|---|
The Oleška in Košťálov | |
![]() | |
| Location | |
| Country | Czech Republic |
| Regions | |
| Physical characteristics | |
| Source | |
| • location | Studenec, Giant Mountains Foothills |
| • elevation | 538 m (1,765 ft) |
| Mouth | |
• location | Jizera |
• coordinates | 50°36′4″N 15°19′54″E / 50.60111°N 15.33167°E |
• elevation | 316 m (1,037 ft) |
| Length | 36.0 km (22.4 mi) |
| Basin size | 171.3 km2 (66.1 sq mi) |
| Discharge | |
| • average | 1.74 m3/s (61 cu ft/s) near estuary |
| Basin features | |
| Progression | Jizera→ Elbe→ North Sea |
The Oleška is a left tributary of the Jizera River in the Czech Republic. It flows through the Liberec and Hradec Králové regions. It is 36.0 km (22.4 mi) long.

The Oleška originates in the territory of Studenec in the Giant Mountains Foothills at an elevation of 538 m (1,765 ft) and flows to Semily, where it enters the Jizera River at an elevation of 316 m (1,037 ft). It is 36.0 km (22.4 mi) long.[1] Its drainage basin has an area of 171.3 km2 (66.1 sq mi).[2]
The longest tributaries of the Oleška are:[1]
| Tributary | Length (km) | Side |
|---|---|---|
| Popelka | 13.1 | left |
| Tampelačka | 10.1 | right |
| Rokytka | 7.8 | left |
The river flows through the municipal territories of Studenec, Levínská Olešnice, Stará Paka, Bělá, Libštát, Košťálov, Slaná and Semily.
Fish species that live in the river include brown trout, rainbow trout, brook trout and grayling.[3]