Spatio-temporal changes and driving factors of wetlands in the delta of the Syr Darya River-Aral Sea during 1962-2019

The changing environment around the Aral Sea has a great impact on the ecological stability of the arid area in Central Asia, to this end, the study on the wetland evolution of the Syr Darya-Aral Sea delta is of great significance to gain further insight in the changing valley and find out the solution for ecological recovery. Based on the multi-source remote sensing data, this paper extracted the wetland information from images by an object-oriented hierarchical extraction method, and analyzed temporal and spatial variations in the delta wetland of the lower of the Syr Darya River from1962 to 2019. Also, this paper took such elements as the changes of the Aral Sea and the farmlands, river discharges, the water conservancy projects and others into consideration and discussed the drivers of the near 60 a wetland changes. This study shows that as the constant shrink of the Aral Sea, the landmass of delta wetland of the lower of the Syr Darya River decreased first, then it grew bigger. During this period, the rate of change presents-38.29 km²/a, 193.35 km²/a and 14.36 km²/a in 3 phases: 1962-1980, 1981-1991 and 1992-2019 respectively. The wetland change has a distinctive spatial variation. Since 1980, two wetlands laying near the northern and the south estuaries of the Syr Darya River have largely expanded towards the Aral Sea. The area between the wetlands and the farmlands has extended to two sides of the river since 1991.Given the fact of the reduced runoff entering the delta after 1962, the irrigation network project and the ecological water allocation play the main role in growing the delta wetland. On the other hand, these projects indirectly cut down the flow entering the Aral Sea, which leads to the rapid shrink of the Aral Sea. The delta wetland recovery poses a striking contrast with the degradation of the Aral Sea. In this case, the ecological environment around the Aral Sea will undergo an inferior recovery.