Lonau (river)
| Location | north of Herzberg am Harz in Osterode am Harz in Lower Saxony,  Germany |
|---|---|
| Length | ca. 3.5 km |
| Confluence | of the Großer and Kleiner Lonau in Lonau 51°41′24″N 10°21′33″E / 51.690028°N 10.359028°ECoordinates: 51°41′24″N 10°21′33″E / 51.690028°N 10.359028°E |
| Source height | unter 340 m |
| Mouth | Sieber 51°39′43″N 10°20′50″E / 51.661806°N 10.34722°E |
| Mouth height | unter 260 m |
| Descent | ca. 80 m |
| Basin | Sieber → Oder → Rhume → Leine → Aller → Weser |
| Catchment | ca. 14 km² |
| Small towns | Herzberg am Harz |
The Lonau is a roughly 3.5 km long (from Lonau) tributary of the Sieber. It starts in Lonau, formed by the confluence of the Große and Kleine Lonau. It then flows in a southerly (intermittently in a south-southwesterly) direction to Herzberg am Harz, where it discharges into the Sieber after the Lonau Waterfall.