Lake Balkhash
Lake Balkhash, also known as Lake Balqash, is a lake in southeastern Kazakhstan. It is one of the largest lakes in Asia and the 15th largest in the world. It is located in the eastern part of Central Asia and sits in the Balkhash-Alakol Basin, an endorheic basin. The basin drains seven rivers, the primary of which is the Ili, bringing most of the riparian inflow; others, such as the Karatal, bring surface and subsurface flow. The Ili is fed by precipitation, largely vernal snowmelt, from the mountains of China's Xinjiang region.
The lake currently covers about. However, like the Aral Sea, it is shrinking due to diversion and extraction of water from its feeders. The lake has a narrow, quite central, strait. The lake's western part is fresh water and its eastern half is saline. The eastern part is on average 1.7 times deeper than the west. The largest shore city is named Balkhash and has about 66,000 inhabitants. Main local economic activities include mining, ore processing and fishing.
There is concern about the lake's shallowing due to desertification of microclimates and water extraction for multiplied industrial output. Moreover, the impacts of climate change may also negatively affect the lake and its ecosystems.
History and naming
The present name of the lake originates from the word "balkas" of Tatar, Kazakh and Southern Altai languages which means "tussocks in a swamp".From as early as 103 BC up until the 8th century, the Balkhash polity surrounding the lake, whose Chinese name was Yibohai 夷播海, was known to the Chinese as 布谷/布庫/布蘇 "Bugu/Buku/Busu." From the 8th century on, the land to the south of the lake, between it and the Tian Shan mountains, was known in Turkic as Jetisu "Seven Rivers". It was a land where the nomadic Turks and Mongols of the steppe mingled cultures with the settled peoples of Central Asia.
Beginning in 1759, the lake marked the northwesternmost limit of Qing suzerainty as recognized by the Qing and Russians. In 1864, the lake and its neighboring area were ceded to the Russian Empire under the Treaty of Tarbagatai. With the dissolution of the Soviet Union in 1991, the lake became part of Kazakhstan.
The origin of the lake
Balkhash lies in the deepest part of the vast Balkhash-Alakol depression, which was formed by a sloping trough between mountains of the Alpine orogeny and the older Kazakhstan Block during the Neogene and Quaternary. Rapid erosion of the Tian Shan has meant the depression subsequently filled with sand river sediments in what is geologically a very short timespan. The basin is a part of Dzungarian Alatau, which also contains lakes Sasykkol, Alakol and Aibi. These lakes are remnants of an ancient sea which once covered the entire Balkhash-Alakol depression, but was not connected with the Aral–Caspian Depression.Description
All the rivers of this region that carry their waters from high mountains flow into Lake Balkhash, however, none of them flows out. The major ones are: Ili, Aksu and Karatal. River Tokrau flows from the north, but its waters get lost in the sands before reaching the lakeshore. The lake is divided into two parts by the Saryesik peninsula. These two parts are connected by the Uzynaral strait. In ancient times Balkhash was much larger and many lakes in the area were part of it, such as Zhalanashkol, Itishpes, Alakol and Sasykkol. Even farther back it was a sea, stretching all the way to the Dzungarian Alatau.As recently as 1910 the lake was considerably larger with an estimated area of 23,464 km2. By 1946 this had shrunk by a nearly third, to 15,730km2.
Relief
The lake has a surface area of about 16,400km2, making it the largest lake wholly in Kazakhstan. Its surface is about 340 m above sea level. It has a gentle curve shape yet with jagged shorelines. Its length is about 600 km and the width varies from 9–19km in the eastern part to 74km in the western part. Saryesik Peninsula, near the middle of the lake, hydrographically divides it into two very different lakes. The western lake covers 58% of the surface area but only 46% of the volume. It is thus relatively shallow, quiet and filled with freshwater. The eastern lake is much deeper and saltier. These parts are connected by the Uzynaral Strait – 3.5km wide and about 6 metres deep.The lake includes several small basins. In the western part, are two depressions 7–11 meters deep. One extends from the western coast to Cape Korzhyntubek, whereas the second lies south from the Gulf Bertys, which is the deepest part of the "half". The average depth of the eastern basin is 16 m and the maximum depth is 26 m.
The average depth of the lake is 5.8 metres, and the total volume of water is about 112km3.
The western and northern shores of the lake are high and rocky; they are composed of such Paleozoic rocks as porphyry, tuff, granite, schist and limestone and keep traces of ancient terraces. The southern shores near the Gulf Karashagan and Ili River are low and sandy. They are often flooded and therefore contain numerous water pools. Occasional hills are present with the height of 5–10 m. The coastline is very curvy and dissected by numerous bays and coves. The large bays of the western part are: Saryshagan, Kashkanteniz, Karakamys, Shempek, and Balakashkan Ahmetsu, and those in the eastern part are: Guzkol, Balyktykol, Kukuna, Karashigan. The eastern part also includes peninsulas Baygabyl, Balay, Shaukar, Kentubek and Korzhintobe.
The lake contains 43 islands with a total area of 66km2; however, new islands are being formed due to the lowering of water level, and the area of the existing ones is increasing. The islands of the western part include Tasaral and Basaral, as well as Ortaaral, Ayakaral and Olzhabekaral. The eastern islands include Ozynaral, Ultarakty, Korzhyn and Algazy.
Feeding the lake and the water level
The Balkhash-Alakol Basin covers 512,000 km2, and its average surface water runoff is 27.76km3/year, of which 11.5km3 comes from China. The drainage basin of the lake is about 413,000km2; with 15% in the north-west of Xinjiang in China and a negligible part from mountains along the Kyrgyz-Kazakh border. Lake Balkhash thus takes 86% of water inflow from Balkhash-Alakol basin.The Ili accounts for 73–80% of the inflow: 12.3km3/year or 23km3 per year. The river rises in a very long, narrow, high sided valley lined by the Tian Shan mountains and is mainly fed by glacier. These have a sporadic degree of relief precipitation, their predominant type. Inflow is often greatest and most regulated during the glacial melting season: June to July. The river forms a quite narrow delta of 8,000km2 that serves as an multi-year accumulator type of regulator.
The eastern part of the lake is fed by the rivers Karatal, Aksu and Lepsy, as well as by groundwater. The Karatal rises on the slopes of Dzungarian Alatau and is the second-largest inflow. The Ayaguz, which fed the east half until 1950, seldom reaches Lake Balkhash.
The western half's inflow averages 1.15km3 greater, per year.
The area and volume vary due to long-term and short-term fluctuations in water level. Long-term fluctuations had an amplitude of 12–14 metres. Since the year 0 CE they saw minimal water between the 5th and 10th centuries; and maximal between the 13th and 18th centuries. In the early 20th century and between 1958 and 1969, the lake swelled to cover about 18,000km2. In droughts such as the late 1900s, 1930s and 1940s, the lake shrank to about 16,000 km2 having a drop in level of about 3 metres. In 1946, the lake's surface area was 15,730km2 . Since the late 1900s, the lake has been shrinking due to the diversion of the rivers supplying it. For example, Kapshagay Hydroelectric Power Plant was built on the Ili in 1970. Filling the associated Kapshagay Reservoir disbalanced the lake, worsening water quality, especially in the eastern part. Between 1970 and 1987, the water level fell by 2.2 metres, the volume reduced by 30 km3 and salinity in the west half was increasing. Projects were proposed to slow down the changes, such as by splitting the lake in two with a dam, called off as the Soviet Union saw recession, democratisation and secession.
The minimal water level of recent decades was in 1987, when the filling of Kapshagay Reservoir was completed. The level recovered to 342.5 m by January 2005, attributed to exceptional precipitation in the late 1990s.
Water composition
Balkhash is a semi-saline lake. Chemical composition strongly depends on the hydrographic features of the reservoir. Water in the west half is nearly fresh, with the content of total dissolved solids about 0.74 g/L, and cloudy ; it is used for drinking and industry. The east half has less silt in suspension but resembles oceanic sea water in salinity, with concentration of 3.5–6 g/L. The average salinity of the lake is 2.94 g/L. Long-term average precipitation of salts in the lake is 7.53 million tonnes and the reserves of dissolved salts are about 312 million tonnes. The water in the western part has a yellow-gray tint, and in the eastern part the color varies from bluish to emerald-blue.Climate
The climate of the lake area is continental. The average mean temperature is about 24 °C with highs in July and the average mean temperature is −14°C in January. Average precipitation is 131mm per year and the relative humidity is about 60%. Wind, dry climate and high summer temperatures result in high evaporation rate – 950 mm in cold and up to 1200mm in dry years. Wind has average speed of 4.5–4.8m/s and blows mainly southward in the western part and to the south-west in the eastern part. The wind induces waves up to 2–3.5 m in height and steady clockwise currents in the western part.There are 110–130 sunny days per year with the average irradiance of 15.9 MJ/m2 per day. Water temperature at the surface of the lake varies from 0 °C in December to 28 °C in July. The average annual temperature is 10°C in the western and 9°C in the eastern parts of the lake. The lake freezes every year between November and early April, and the melting is delayed by some 10–15 days in the eastern part.