Geospatial quantitative analysis of the Aral Sea Shoreline changes using RS and GIS techniques

The variations in the lake area, water level, and water volume change of the Aral Sea from 1987 to 2018 were analyzed in this study, which is based on the multi-temporal Landsat images and remote sensing water body index (Normalized Difference Water Index, NDWI). Lake shorelines were automatically digitized and visualized using Net Shoreline Movement (NSM) and Linear Regression Rate (LRR) by Digital Shoreline Analysis System (DSAS). The surface area, water level, and water volume change of the North Aral Sea were not changed significantly in 1987-2018. The maximum lake area appeared in March 2015 with 3550.15 km², the minimum lake area appeared in October 2001with 2830.56 km². However, since 2010 the South Aral Sea split into the East Aral Sea and the West Aral Sea, the area change has shrunk dramatically. The area of the East Aral Sea decreased by 17852.65 km² (89.99 %) from March 2011 to September 2018. The area of the West Aral Sea decreased by 2203.62 km² (35.96 %) from August 2014 to March 2017. The distance of lake shoreline changes and rates of net movement along transects were determined by DSAS. The two largest positive values of NSM were 18715.93 and 12268.67 m, which showed lake shoreline retreat, occurred in the periods of 2010-2018 in the East Aral Sea and 1987-1999 in the South Aral Sea, respectively. The two periods in which the largest negative value of NSM appeared was (1987-1993) and (2001-2010) in the North Aral Sea, and the lake shoreline expanding distance was 145.43 and 545.84 m, respectively.