Abstract
The Aral Sea was the fourth largest inland lake on the globe until 1960, with a surface area of about 68,000 km2. Mainly, the huge irrigation projects in many parts of its transboundary catchment were responsible for the catastrophic desiccation and ecological crises of the Aral Sea after second part of 20th century. Ecological crisis surrounding the Aral Sea (lake) regions is one of the critical environmental problems of Central Asia. As a result, monitoring of desertification processes and determining the aerosol concentration in the atmosphere are highly relevant for any attempts to mitigate environmental changes in the Aral Sea basin. Remote sensing is the most appropriate method for studying desertification and dust storms as it easily covers large areas with a high spatial and temporal resolution. Satellite images provide detailed multispectral information about the earth’s surface features, which proves invaluable for the characterization of vegetation, soil, water, and landforms at different scales. Vegetation cover, biomass, and soil properties were analyzed with remote sensing methods (NDVI, SDVI). It is emphasized that vegetation indices have little sensitivity at low leaf area which is common to all desert ecosystems.
Highlights
The immediate cause of the lake water disappearance of the Aral Sea is the fact that its two major rivers, the Amu Darya and Syr Darya, only contributed an average of 5 km3 of water to the lake's annual water balance instead of the former quantity of 56 km3
Conducted an in-depth and systematic analysis of long-term space and time variations in of both area and water volume of the Aral Sea, and their potential drivers, which was lacking prior to these experiments[47, 42, 28, 9, 26]. They extracted the lake surface area of the Aral Sea using one of the Remote Sensing (RS) indices, Normalized Difference Vegetation Index (NDVI), based on the dataset captured by MODIS during 2000-2018. This extraction enabled to quantify and distinguish the inter-annual variations of lake surface area and water volume of the Aral Sea during 1960–2018 based on long-term hydrological data generated by the MODIS sensor
Considering the above mentioned results, this paper aims to provide an improved insight to spatio-temporal land-cover change, aligning with water shrinkage, from 1960 in the Aral Sea was change water balance and start shrinking but in the last two decades and to determine a water shrinkage rate per annum based on Landsat sensor
Summary
The immediate cause of the lake water disappearance of the Aral Sea is the fact that its two major rivers, the Amu Darya and Syr Darya, only contributed an average of 5 km of water to the lake's annual water balance instead of the former quantity of 56 km. Conducted an in-depth and systematic analysis of long-term space and time variations in of both area and water volume of the Aral Sea, and their potential drivers, which was lacking prior to these experiments[47, 42, 28, 9, 26] They extracted the lake surface area of the Aral Sea using one of the Remote Sensing (RS) indices, Normalized Difference Vegetation Index (NDVI), based on the dataset captured by MODIS during 2000-2018. This extraction enabled to quantify and distinguish the inter-annual variations of lake surface area and water volume of the Aral Sea during 1960–2018 based on long-term hydrological data generated by the MODIS sensor The results of these experiments revealed that from 1960 to 2018 the area of the Aral Sea shrank dramatically and the average water shrinkage rate per annum accounted for around 1,000 km. These two lakes have encountered opposing trends: the much bigger South Aral Sea located in Uzbekistan has shrunk dramatically despite having some trend oscillations, while the North Aral Sea located in Kazakhstan has enlarged obscurely [1]
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