Zun-Torey

The Torey Lakes are a pair of soda lakes, Barun-Torey and Zun-Torey, in Russia's Zabaykalsky Krai, on the border with Mongolia — the Mongolia–Russia border runs across the southern tip of Zun-Torey lake.

Geography and hydrography

The two lakes are the remains of a large lake or sea whose surface, according to Shamsutdinov (1983), once reached some 700,000 years ago.
They are the largest soda lakes in the arid zone
in the trans-Baikal region.
They lie close to one another, connected by the Utochi channel,
in a closed basin with no outlet to the sea.

The size and volume of water in the lakes varies greatly with the region's multi-decadal rainfall and climate cycles. These interdecadal cycles last from 27 years to 35 years; they depend on variations in atmospheric moistening: relatively moist and very cold periods alternate with dry and relatively warm periods.
For example, Barun-Torey lake completely dried up in summer 2009, and started refilling in 2013; Zun-Torey lake dried up in autumn 2017.
The dry bed of Barun-Torey lake is strewn with temporary freshwater pools fed by groundwater and precipitations, even though that groundwater is not necessarily freshwater.
These pools are alkaline, with a pH around 8.2 – 9.0; they are oligohaline (0.5–1.0 g × l-1), rather warm (26 to 30°С), most are muddy (TR = 0.1–0.3 m). Those at the western shore of the lake are fed by groundwater discharge through a geological fracture.

In periods of high water level, Barun-Torey lake and Zun-Torey lake have the same hydrochemical parameters: oligohaline and alkaline.

File:ISS006-E-47710 - View of Torey Lakes.jpg, Satellite view: Zun-Torey lake on the right (east), Barun-Torey lake on the left (west). April 2003
File:ISS023-E-47759 - View of Earth.jpg, Zun-Torey lake on the right (east), Barun-Torey lake on the left (west). May 2010

Barun-Torey

During high-water years, Barun-Torey lake has an area of , with a volume of ; the average depth is 2.5 m, with a maximum depth of 4.3 m. In low-water years, the lake shrinks dramatically and can dry up completely. The southern end of the lake extends into Mongolia.

Barun-Torey lake is fed by two rivers. The Ulz River (Uldza River or Ulz Gol) flows into the lake from the south and forms a large estuary. The Imalka River flows into the lake from the west.

When the water level reaches 596.1 m in elevation, Barun-Torey water starts running off into Zun-Torey lake via the Utochi channel. Once the surfaces of the two lakes are levelled up, the wind and other factors induce changes in the direction of the current in the channel. When the water level falls, the shallower Barun-Torey lake dries up quicker and the water in the Utochi channel flows from Zun-Torey lake to Barun-Torey lake.
As the lake level falls and during the initial refilling of the lake, three stages of changes in the planktonic associations have been identified; the plankton communities increase in species richness and abundance in the transient pools.

File:ISS022-E-34463 - View of Earth.jpg, Northern end of the dried-up lake. January 2010
File:ISS023-E-47752 - View of Earth.jpg, Southern shore of the lake, in Mongolia. May 2010

Zun-Torey

Lake Zun-Torey lies east of Lake Barun-Torey. During high water, the lake has a surface area of 285 km² and a volume of 1.6 km³; but in 1999 its surface reached 301.6 km² and in 2015 it reached 254 km².
The average depth is 4.5 m, and the maximum depth (in the northern part of the lake, where the lake bed drops steeply from the shore) is 6.7 m; its length is 23 km and its width is 13 km. The lake is round and has a single island, which turns into a peninsula when the water level is low. Lake Zun-Torey is mostly fed by the channel from Lake Baran-Torey, and does not dry as extensively or vary in extent as much as Lake Baran-Torey does.

During the aridification of Zun-Torey lake, four stages of changes in the planktonic associations were identified; the phytoplankton decreased in abundance and biomass, and was dominated by green algae and diatoms; the number of zooplankton species decreased but zooplankton's total abundance and biomass increased as the number of individuals increased in some crustacean species.

File:Озеро Зун-Торей (5).JPG, North coast. June 28, 2010
File:ISS019-E-6029 - View of Earth.jpg, East point of the lake. April 2009

Ecology

The lakes and their environs are home to 305 bird species (including 90 breeding species), 42 species of mammals, various reptile, amphibian, and fish species, and over 590 insect species.

The lakes and surrounding wetlands are an important breeding, feeding and staging area for many species of migratory waterbirds, including several rare and threatened species. The lakes support significant breeding populations of several threatened bird species, including the red-crowned crane (''Grus japonensis''), white-naped crane (''Grus vipio''), swan goose (''Anser cygnoides''), great bustard (''Otis tarda''), and relict gull (''Ichthyaetus relictus''). The lakes are located on East Asian–Australasian Flyway, and millions of birds pass through the Torey Lakes and nearby wetlands in spring and autumn. The lakes provide migratory habitat for the critically endangered Siberian crane (''Grus leucogeranus'') and threatened hooded crane (''Grus monacha'').

Traditional agriculture, fishing, and animal husbandry are important to the local population.

Protected areas

An area of , including both lakes and adjacent wetlands and uplands, was designated a Ramsar Site