Ulakhan-Botuobuya

The Ulakhan-Botuobuya (Улахан-Ботуобуя or Большая Ботуобуя; "Big Botuobuya"; Улахан Ботуобуйа, Ulaxan Botuobuya) is a river in Yakutia (Sakha Republic), Russia. It is a right hand tributary of the Vilyuy, with a length of 459 km and a drainage basin area of 17500 km2.

The river flows across mostly uninhabited territory of Mirninsky District. Botuobuyinsky Nasleg is located in its middle course. There is a pontoon bridge of the A331 highway stretch between Mirny and Udachny crossing the river just before its confluence with the Vilyuy.

Course
The Ulakhan-Botuobuya begins in the Lena Plateau at an elevation of 317 m. It flows first roughly eastwards and then northeastwards across the Vilyuy Plateau within a wide valley. Finally it bends again and heads northwards. The smaller Ochchuguy-Botuobuya runs roughly parallel to it further to the east. Finally the Ulakhan-Botuobuya joins the right bank of the Vilyuy 1294 km from its mouth, a few miles downstream of the Vilyuy Dam. The river freezes between October and late May.

The largest tributary of the Ulakhan-Botuobuya is the 58 km long Tas-Yuryakh (Таас-Юрэх) that joins it from the right.