Sustainable water management for cross-border resources: The Balkhash Lake Basin of Central Asia, 1931-2015

The water level in Balkhash Lake is an important indicator for basin-wide ecosystem conditions, which is affected by many factors. The Ili River is a typical trans-boundary river between China and Kazakhstan, and its flows occupy about 80% of the runoff of all rivers flowing into Balkhash Lake. Several studies argued that overexploitation of water resources on the China side caused the decrease of river discharge of the Ili River, eventually leading to the decline of the Balkhash Lake's water level. This study uses trend and correlation analysis to characterize variations in lake level, precipitation, temperature, evapotranspiration, land cover and population in the Balkhash Lake Basin. Results show that a substantial increase in the amount of discharges that flows from China to Kazakhstan has been observed from 1931 to 2013, and the average annual discharge from 1998 to 2013 reflects a 26.5% increase (36.33 x 10(8) m(3)) over the average from 1931 to 1997. The Kapchagay reservoir significantly reduced annual river discharges by about 11.67 x 10(8) m(3) during the period 1970-1997, which significantly caused the decline of the Balkhash Lake's levels. Agricultural land increased by 0.74 x 10(3) km(2)/year from 1992 to 2015, mainly in the southeast of Kazakhstan during the period 1998-2001, leading to an increasing trend in water consumption due to evapotranspiration from increasing irrigation. Overall, water resources are in long-term decline in the Balkhash Lake Basin when glaciers melt and irrigation must therefore be managed with increasing efficiency. The results presented here provide essential information for a comprehensive understanding of lake and water resources allocation and management. (C) 2020 Elsevier Ltd. All rights reserved.