Lake Baikal in the context of "Irkutsk Oblast"

The Caspian Sea is the world's largest inland body of water, described as the world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it is situated in both Europe and Asia: east of the Caucasus, west of the broad steppe of Central Asia, south of the fertile plains of Southern Russia in Eastern Europe, and north of the mountainous Iranian Plateau. It covers a surface area of 371,000 km (143,000 sq mi) (excluding the highly saline lagoon of Garabogazköl to its east), an area approximately equal to that of Japan, with a volume of 78,200 km (19,000 cu mi). It has a salinity of approximately 1.2% (12 g/L), about a third of the salinity of average seawater. It is bounded by Kazakhstan to the northeast, Russia to the northwest, Azerbaijan to the southwest, Iran to the south, and Turkmenistan to the southeast. The name of the Caspian Sea is derived from the ancient Iranic Caspi people.

The lake stretches 1,200 km (750 mi) from north to south, with an average width of 320 km (200 mi). Its gross coverage is 386,400 km (149,200 sq mi) and the surface is about 27 m (89 ft) below sea level. Its main freshwater inflow, Europe's longest river, the Volga, enters at the shallow north end. Two deep basins form its central and southern zones. These lead to horizontal differences in temperature, salinity, and ecology. The seabed in the south reaches 1,023 m (3,356 ft) below sea level, which is the third-lowest natural non-oceanic depression on Earth after Baikal and Tanganyika lakes.

The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Superior, Michigan, Huron, Erie, and Ontario (though hydrologically, Michigan and Huron are a single body of water, joined at the Straits of Mackinac). The Great Lakes Waterway enables modern travel and shipping by water among the lakes. The lakes connect ultimately to the Atlantic Ocean via the Saint Lawrence River as their primary drainage outflow. The lakes are also connected to the Mississippi River basin through the Illinois Waterway.

The Great Lakes are the largest group of freshwater lakes on Earth by total area and the second-largest by total volume. They contain 21% of the world's surface fresh water by volume. The total surface is 94,250 square miles (244,106 km), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km), slightly less than the volume of Lake Baikal (5,666 cu mi or 23,615 km, 22–23% of the world's surface fresh water). Because of their sea-like characteristics, such as rolling waves, sustained winds, strong currents, great depths, and distant horizons, the five Great Lakes have long been called inland seas. Depending on how it is measured, by surface area, either Lake Superior or Lake Michigan–Huron is the second-largest lake in the world and the largest freshwater lake. Lake Michigan is the largest lake, by surface area, that is entirely within one country, the United States.

The Russian Far East (Russian: Дальний Восток России, IPA: [ˈdalʲnʲɪj vɐˈstok rɐˈsʲiɪ]) is a region in North Asia. It is the easternmost part of Russia and the Asian continent, and is coextensive with the Far Eastern Federal District, which encompasses the area between Lake Baikal and the Pacific Ocean. The area's largest city is Khabarovsk, followed by Vladivostok. The region shares land borders with the countries of Mongolia, China, and North Korea to its south, as well as maritime boundaries with Japan to its southeast, and with the United States along the Bering Strait to its northeast.

Although foreign sources often consider the Russian Far East to be a part of Siberia, it has been historically categorized separately from Siberia in Russian regional schemes (and previously during the Soviet era when it was called the Soviet Far East).

An ecosystem, short for ecological system, is defined as a collection of interacting organisms within a biophysical environment. Ecosystems are never static, and are continually subject to both stabilizing and destabilizing processes. Stabilizing processes allow ecosystems to adequately respond to destabilizing changes, or perturbations, in ecological conditions, or to recover from degradation induced by them. Yet, if destabilizing processes become strong enough or fast enough to cross a critical threshold within that ecosystem, often described as an ecological 'tipping point', then an ecosystem collapse (sometimes also termed ecological collapse) occurs.

Ecosystem collapse does not mean total disappearance of life from the area, but it does result in the loss of the original ecosystem's defining characteristics, typically including the ecosystem services it may have provided. Collapse of an ecosystem is effectively irreversible more often than not, and even if the reversal is possible, it tends to be slow and difficult. Ecosystems with low resilience may collapse even during a comparatively stable time, which then typically leads to their replacement with a more resilient system in the biosphere. However, even resilient ecosystems may disappear during the times of rapid environmental change, and study of the fossil record was able to identify how certain ecosystems went through a collapse, such as with the Carboniferous rainforest collapse or the collapse of Lake Baikal and Lake Hovsgol ecosystems during the Last Glacial Maximum.

Lake Tanganyika (/ˌtæŋɡənˈjiːkə, -ɡæn-/ TANG-gən-YEE-kə, -⁠gan-; Kirundi: Ikiyaga ca Tanganyika) is an African Great Lake. It is the world's second-largest freshwater lake by volume and the second deepest, in both cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. It is also the 6th largest lake by area. The lake is shared among four countries—Tanzania, the Democratic Republic of the Congo (the DRC), Burundi, and Zambia—with Tanzania (46%) and the DRC (40%) possessing the majority of the lake. It drains via the Lukuga River into the Congo River system, which ultimately discharges at Banana, Democratic Republic of the Congo into the Atlantic Ocean.

The Buryats are a Mongolic ethnic group native to southeastern Siberia who speak the Buryat language. They are one of the two largest indigenous groups in Siberia, the other being the Yakuts. The majority of the Buryats today live in their titular homeland, the Republic of Buryatia, a federal subject of Russia which sprawls along the southern border and partially straddles Lake Baikal. Smaller groups of Buryats also inhabit Ust-Orda Buryat Okrug (Irkutsk Oblast) and the Agin-Buryat Okrug (Zabaykalsky Krai) which are to the west and east of Buryatia respectively as well as northeastern Mongolia and Inner Mongolia, China. Traditionally, they formed the major northern subgroup of the Mongols.

Buryats share many customs with other Mongolic peoples, including nomadic herding, and erecting gers for shelter. Today the majority of Buryats live in and around Ulan-Ude, the capital of the Buryat Republic, although many still follow a more traditional lifestyle in the countryside. They speak a central Mongolic language called Buryat. UNESCO's 2010 edition of the Atlas of the World's Languages in Danger classifies the Buryat language as "severely endangered".

The Yenisey or Yenisei (/ˌjɛnɪˈseɪ/ YEN-iss-AY; Russian: Енисе́й, pronounced [jɪnʲɪˈsʲej]) is the fifth-longest river system in the world, and the largest to drain into the Arctic Ocean.

Rising in Mungaragiyn-gol in Mongolia, it follows a northerly course through Lake Baikal and the Krasnoyarsk Dam before draining into the Yenisey Gulf in the Kara Sea. The Yenisey divides the Western Siberian Plain in the west from the Central Siberian Plateau to the east; it drains a large part of central Siberia. Its delta is formed between the Gyda Peninsula and the Taymyr Peninsula.

Buryatia, officially the Republic of Buryatia, is a republic of Russia located in the Russian Far East. Formerly part of the Siberian Federal District, it has been administered as part of the Far Eastern Federal District since 2018. To its north lie Irkutsk Oblast and Lake Baikal, the deepest lake in the world; Zabaykalsky Krai to the east; Tuva to the west and Mongolia to the south. Its capital is the city of Ulan-Ude. It has an area of 351,300 square kilometers (135,600 sq mi) with a population of 978,588 (2021 Census). It is home to the indigenous Buryats.