Inter-annual water storage changes in the Aral Sea from multi-mission satellite altimetry, optical remote sensing, and GRACE satellite gravimetry

The estimation of water storage variations in lakes is essential for water resource management activities in a region. In areas of ungauged or poorly gauged water bodies, satellite altimetry acts as a powerful tool to measure changes in surface water level. Remote sensing provides images of temporal coastline variations, and a combination of both measurement techniques can indicate a change in water volume. In this study variations of the water level of the Aral Sea were computed for the period 2002-2011 from the combination of radar and laser satellite altimetry data sets over the lake. The estimated water levels were analyzed in combination with coastline changes from Landsat images in order to obtain a comprehensive picture of the lake water changes. In addition to these geometrical observations temporal changes of water storage in the lake and its surrounding were computed from GRACE satellite gravimetry. With respect to its temporal evolution the GRACE results agree very well with the geometrical changes determined from altimetry and Landsat. The advancing desiccation until the beginning of 2009 and a subsequent abrupt gain of water in 2009-2010 due to exceptional discharge from Amu Darya can clearly be identified in all data sets.