Monitoring Surface Water Area Changes in the Aral Sea Basin Using the Google Earth Engine Cloud Platform

The surface water area and types in the Aral Sea Basin (ASB) have undergone extensive changes due to the impacts of climate change and anthropogenic activities. This study explores the changes in the surface water area in the ASB based on the Google Earth Engine cloud platform. Then, we integrate multi-source data to identify 1559 lakes and 196 reservoirs from the Joint Research Centre Global Surface Water (JRC GSW) dataset. Our results indicate that the lake area (34,999.61 km(2)) is about 10 times that of the reservoir area (3879.08 km(2)) in the ASB. The total area of surface water in the ASB decreased by 23,194.35 km(2) or 34.58% from 1992 to 2020. Specifically, the areas of permanent water shrunk at a rate of 1278.6 km(2)/year, while the areas of seasonal water increased at a rate of 522.5 km(2)/year. The proportion of lakes and reservoirs in the total surface water has decreased from 79.33% (during 1992-2000) to 75.21% (during 2000-2010) to 63.94% (during 2010-2020). The water that should have flowed into the Aral Sea to maintain its permanent water may have been converted into two parts. Part of it might continue to be permanent water but show up in other regions, while part of it might convert to seasonal water (especially in the Aral Sea itself and the ASB plain area). Our study bridges the limitations of previous studies that have ignored seasonal water change and builds a water area list for 1755 lakes/reservoirs (=0.1 km(2)) for the first time. The results can serve as important knowledge for water resource management and sustainable river basin development in ASB.