Lake Balkhash - Feeding The Lake and The Water Level

Feeding The Lake and The Water Level

Balkhash-Alakol Basin covers an area of 512,000 km2, and its average surface water runoff is 27.76 km3/year, of which 11.5 km3 come from the territory of China. The area of drainage basin of the lake is about 413,000 km2; with 15% belonging to the north-west of Xinjiang region in China and a small part in Kyrgyzstan. Lake Balkhash takes 86% of water inflow from Balkhash-Alakol basin. Ili River accounts for 73–80% of the inflow with the total volume quoted as either 12.3 km3/year or 23 km3/year. The river originates in Tian Shan mountains and is mainly fed by glacier. This results in daily and seasonal fluctuations of its water level with a strong increase during the glacier melting season in June–July. The river forms an extended delta which covers the area of 8,000 km2 and serves as an accumulator, providing water in the drought years.

The eastern part of the lake is fed by the rivers Karatal, Aksu and Lepsa, as well as by groundwater. The Karatal River originates on the slopes of Dzungarian Alatau and is the second largest water source for the lake. River Ayaguz, which fed the eastern part of the lake until 1950, barely reaches it nowadays. The annual difference in the flow to the western and eastern parts of the lake is 1.15 km3.

The area and volume of the lake vary due to long-term and short-term fluctuations in water level. Long-term fluctuations had an amplitude of 12–14 m, which was minimum between the 5th and 10th centuries and maximum between the 13th and 18th centuries. In the early 20th century and between 1958 and 1969, the area of the lake increased to ~18,000 km2, and during the droughts, for example in the late 1900s, 1930s and 1940s, the lake shrank to ~16,000 km2 with the water level fluctuations of about 3 m. In 1946, the area was 15,730 km2 and the lake volume was 82.7 km3. From the late 1900s, the lake is shrinking due to the diversion of the rivers supplying it. For example, Kapshagay Hydroelectric Power Plant was built on Ili River in 1970. Filling the associated Kapshagay Reservoir disbalanced Balkhash Lake, causing deterioration of water quality, especially in the eastern part of the lake. Between 1970 and 1987, the water level fell by 2.2 m, the volume reduced by 30 km3 and the salinity of the western part was increasing. Projects were proposed to slow the changes down, e.g. by splitting the lake in two with a dam, but were cancelled due to the economic decline in the Soviet Union.

The minimal water level in the lake (340.65 meters above sea level) was recorded in 1987, when the filling Kapshagay Reservoir was completed. The level rose to 342.5 m by January 2005 that was attributed to large volume of precipitations in the late 1990s.