Indigirka
The Indigirka (; ) is a river in the Sakha Republic in Russia between the Yana to the west and the Kolyma to the east. It is long. The area of its basin is . History. The isolated village of Russkoye Ustye, located on the delta of the Indigirka, is known for the unique traditional culture of the Russian settlers whose ancestors came there several centuries ago. Some historians have speculated that Russkoye Ustye was settled by Pomors in the early 17th century. In 1638 explorer Ivan Rebrov reached the Indigirka. In 1636–42 Elisei Buza pioneered the overland route to the Indigirka  river system. At about the same time, Poznik Ivanov ascended a tributary of the lower Lena, crossed the Verkhoyansk Range to the upper Yana, and then crossed the Chersky Range to the Indigirka. In 1642 Mikhail Stadukhin reached the Indigirka overland from the Lena. Zashiversk on the Indigirka was an important colonial outpost during the early days of Russian colonization. It was subsequently abandoned in the 19th century. Other historical settlements, now long abandoned, were Podshiversk and Uyandinskoye Zimov'ye. In 1892–94 Baron Eduard Von Toll carried out geological surveys in the basin of the Indigirka (among other Far-eastern Siberian  rivers) on behalf of the Russian Academy of Sciences. During one year and two days the expedition covered , of which were up rivers, carrying out geodesic surveys en route. Course. It originates at the confluence of the long Tuora-Yuryakh (also known as Khastakh, Khalkan or Kalkan) river and the long Taryn-Yuryakh, both of which originate on the northern slopes of the Khalkan Range. In its higher course, the river flows northwestwards along the Yana-Oymyakon Highlands, through the lowest part of the Oymyakon Plateau. Turning north, it cuts through several subranges of the Chersky Range. At the point  where it crosses the Chemalgin Range the river narrows and flows into a deep gorge, forming rapids. Where it is joined by the Moma river from the southeast, the Indigirka reaches the Momo-Selennyakh Depression, a wide intermontane basin and the middle course of the river begins, where its valley expands. Turning northwards, the Indigirka cuts deeply across the Moma Range and flows northeastwards meandering across the Aby Lowland and widening to 500 m. After flowing between the neck formed by the eastern end of the Polousny Range and the western end of the Ulakhan-Chistay Range, it flows north  with the Kondakov Plateau to the est across the Yana-Indigirka Lowland, part of the greater East Siberian Lowland. Further north, where the terrain becomes completely flat, the Indigirka divides into branches 130 km from the mouth, forming a 5.500 km² wide delta. Its waters end up in the Kolyma Bay, East Siberian Sea. The Indigirka freezes up in October and stays under the ice until May–June. Tributaries. The main tributaries of the Indigirka are, from source to mouth: Ports, settlements and economy. Main ports on the river are: There is a gold prospecting industry in the Indigirka basin . Ust-Nera, a gold-mining center, is the largest settlement on the river. The Indigirka teems with a variety of fishes. Among the most valuable are several whitefish species, such as vendace, chir, muksun, inconnu ("nelma"), omul, etc. Mouths. The Indigirka forms a large delta, consisting of a number of streams (each one being labeled on Russian maps as a "photo ka" (river arm)) and islands. About before reaching the East Siberian Sea (), the river splits into two major northeast-flowing streams. The left (westernmost) arm is known as the "Russko-Ustyinskaya Protoka"; the right arm, the "Srednyaya Protoka" (Russian  for the "Middle Arm"). Further downstream, the third major arm, the "Kolymskaya Protoka" splits off the "Srednyaya Protoka" as its right (eastern) distributary, thus justifying the "middle" moniker for the Srednyaya Protoka. While "Srednyaya Protoka" means the "Middle Arm", the names of the main western and eastern arms indicate their relative location as well. The "Kolymskaya Protoka", or "Kolymskoye Ustye" is the arm one located on the eastern side, i.e. the "Kolyma side" of the delta (the arm closest to the Kolyma, the eastern neighbor of the Indigirka). The "Russko-Ustyinskaya Protoka", apparently known earlier as simply "Russkoye Ustye" is  the arm one located on the western side, i.e. the "Russian side" of the delta (meaning, the side closest to the (European) Russia). These days the name of the "Russko-Ustyinskaya Protoka" appears as if it were formed from the name of the old Russian village Russkoye Ustye situated there, but originally the opposite is likely to have been the case, the village is named after the river arm (the "Russkoye Ustye") on which it was located. Several flat islands are formed by the channels of the delta. Listed from the east to the west, the major ones are: Indigirka