Hydrologic chencles of Aral Sea: A reveal by the combination of radar altimeter data and optical images

Aral Sea has gone through a drastic shrinkage during the past century, from more than 68,000 km(2) in 1960s to less than 10,000 km(2) in 2015. The desiccation was highly severe in 2009 and 2014 due to the west basin changed to an exposed bottom for several months. Then dust storms, fishery recession and degraded plant communities followed, causing tremendous environmental problems and economic deteriorations. In this paper, high frequency water extents of Aral Sea during 2000-2015 were delineated by MODIS images. Water level changes of the lake were analyzed according to a water level database, which was derived on TOPEX/Poseidon, Jason-1, Jason-2, ENVISAT and SARAL altimeter data. Water volume changes during the same period were determined by a combination of lake surface extents and the corresponding water level data. The largest area of Aral Sea was 30,256.46 km(2) in May 2000, and the smallest was 6926.04 km(2) in November 2014. Water storage declination for the whole lake was up to 74km(3) and water level dropped from 43.42 m to 39.73 m during 2000-2015. In a whole, west and east basins of the lake presented declination trends (-191.73 km(2)/yr and -1089.48 km(2)/yr), while the north basin showed a little increase with the rate of 38.18 km(2)/yr. For the three basins (north, west and east), corresponding level tendencies were 0.15 m/yr, -0.5 m/yr, -0.38 m/yr, and volume variations were 0.29 km(3)/yr, -1.36 km(3)/yr, -3.25 km(3)/yr, respectively.