| Tokko | |
| Source1: | Udokan Range Stanovoy Highlands |
| Source1 Coordinates: | 57.2058°N 119.6592°W |
| Source1 Elevation: | 1369m (4,491feet) |
| Mouth: | Chara |
| Mouth Elevation: | 130m (430feet) |
| Mouth Coordinates: | 59.8483°N 120.3736°W |
| Progression: | Chara→ Olyokma→ |
| Subdivision Type1: | Country |
| Subdivision Name1: | Russia |
| Subdivision Type2: | Federal subject |
| Subdivision Name2: | Yakutia |
| Length: | 446km (277miles) |
| Discharge1 Avg: | 220m3/s |
| Basin Size: | 23100km2 |
| Pushpin Map: | Russia Sakha Republic |
| Pushpin Map Caption: | Mouth location in Yakutia, Russia |
The Tokko (Russian: Токко) is a river in Yakutia, East Siberia, Russian Federation. It is the largest tributary of the Chara river in terms of length and area of its basin. The river is long and has a drainage basin of . It is navigable in its final stretch, 131km (81miles) from its confluence with the Chara. Tokko village is located by the river bank.[1]
The Chara-Tokkinskaya group of deposits (Чара-Токкинская группа месторождений), the largest iron ore accumulation in Russia, is located in the Tokko basin. Rock art depictions of ancient hunters dating back to the 1st - 2nd millennia BC have been preserved on a limestone ridge rising 4m (13feet) to 18m (59feet) above the river's right bank 18km (11miles) from its mouth.
The waters of the Tokko are rich in fish, including grayling, lenok, taimen, pike and common dace, among other species.[2]
The Tokko is a right tributary of the Chara, of the Lena basin. Its source is in a glacial lake located on the southeastern slopes of a nameless 2025m (6,644feet) high peak of the Udokan Range, a subrange of the Stanovoy Highlands, very near the border of Transbaikalia.[3] In its upper course the Tokko flows northwards across the Olyokma-Chara Plateau in the Olyokminsky District through a U-shaped valley bound by smooth mountains. At about 362km (225miles) from its mouth the Tokko enters a deep valley where it narrows to a maximum of and forms rapids. 90km (60miles) further downstream, after the confluence of the Choruoda, one of its main tributaries, the Tokko enters a wide floodplain where it slows down, divides into arms and forms meanders. Finally it joins the Chara 73km (45miles) from this river's mouth in the Olyokma.[2]
The longest tributaries of the Tokko are the 145km (90miles) long Choruoda, The 70km (40miles) long Torgo and the 177km (110miles) long Teene (Тээнэ) from the right, and the 71km (44miles) long Kebekte, the 64km (40miles) long Upper Dzhege (Верхняя Джеге) and the 68km (42miles) long Ulakhan-Segeeleennekh (Улахан-Сэгэлээннээх) from the left. The river is frozen in most of its length between mid October and mid May, but there are places where polynyas form. There are about 1,700 lakes in the basin area of the Tokko.[2]