The large , flowing in from the south, spills into the western part of the lake, and it contri.... part lake

The large , flowing in from the south, spills into the western part of the lake, and it contributed 8090 percent of the total influx into the lake until a hydroelectric project reduced the volume of the river's inflow late in the 20th century. Only such small rivers as the Qaratal, Aqsu, Ayaguz, and Lepsi feed the eastern part of the lake. With almost equal areas in both parts of the lake, this situation creates a continuous flow of water from the western to the eastern section. The average annual water temperature in the western part of the lake is 50 F (10 C); in the eastern part it is 48 F (9 C). The fauna of the lake was formerly rich but declined from the 1970s owing to the lake's deteriorating water quality. Before these declines began, 20 species of fish inhabited the lake, of which six were peculiar to the lake itself. The diversion of water to fill the Qapshaghay reservoir and to provide for irrigation reduced the flow of the Ile River by two-thirds and caused a dec! line in the lake's level.