Derba
The Derba (), also known as Derbe (; ) or Dzherba (), is a river in Yakutia (Sakha Republic), Russia. It is a tributary of the Lena with a length of — counting the Mas-Turukhtaakh at its head— and a drainage basin area of . The river flows across an uninhabited area of the Lensky District. Course. The Derba is a left tributary of the Lena. It is formed at the confluence of the Kyuyokh-Ottakh (Кюёх-Оттоох) and Mas-Turukhtaakh (Мас-Турухтаах) rivers in the eastern fringes of the Central Siberian Plateau, to the south of the basin of the Vilyuy. The river  heads in a roughly southern direction across taiga areas dotted with lakes. In its lower course it flows to the east of the Nyuya as it reaches the Lena floodplain and flows slowly in a swampy area. Finally it meets the Lena from its mouth, east of the mouth of the Nyuya. The largest tributaries of the Derba are the long Ergedey (Эргэдьэй) and the long Dyukta that join it from the left. There are 330 lakes in its basin. The Derba freezes yearly between October and May.