Abstract
Understanding the change of river islands is essential for water conservancy construction, channel navigation safety, and industrial/agricultural production. Yangtze River is the largest river in China; however, there are few long-term monitoring results on the changes of Yangtze River islands. To fill this gap, Landsat data available on the Google Earth Engine (GEE) were used to obtain the annual changes of the Yangtze River islands located from the lower reaches of the Three Gorges Dam (TGD) to the Yangtze River delta during 1986-2017. Moreover, we focused on the changes of those islands before and after the construction of the TGD. Annual areas of all river islands were calculated and spatial-temporal pattern of Yangtze River islands were analyzed. Our satellite observation results show continuous expansions of Yangtze River islands after the construction of the TGD in 2003. For the total 138 river islands, in three stages: before 2003, after 2003 and in the 32-year study period, 68, 118, and 124 river islands showed increasing trends, with the net increase of 286.47 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 417.49 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and 665.62 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . For the total 92 river island groups (138 islands), percentages of river island expansion are 41.30% (before 2003), 80.43% (after 2003) and 88.04% (1986-2017). Moreover, we found 10 newly developed river islands, with a net expansion of 87.42 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an expansion rate of 2.73 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /year. The significant decrease (2-4 m) in water level before and after the TGD might be the main factor that results in the observed expansion of Yangtze islands downstream the TGD. We also highlighted the importance of using all available Landsat imagery for tracking the changes of river islands. Our satellite-derived dataset provide reference data for the land use planning and environmental protection in the Yangtze River drainage basin.
Highlights
At present, owing to the increasing energy demand induced by rapid growth of human populations and economic development, new sources of renewable energy are urgently required [1]
From the two sub images, the omission errors are mainly distributed in the island boundary region, and the commission errors are mainly distributed within the island
In this paper, from 1986 to 2017, satellite observation results of all river islands in the Yangtze River downstream of the Three Gorges Dam (TGD) were obtained from all Landsat data provided by Google Earth Engine (GEE) platform within the study period
Summary
At present, owing to the increasing energy demand induced by rapid growth of human populations and economic development, new sources of renewable energy are urgently required [1]. To fill the current energy gap, a large number of hydropower stations have been constructed along various rivers around the world over the past decades for the. Increasing electricity demand, and many dams and reservoirs were established for the impoundment [2]. Those hydropower stations can produce many benefits, such as hydropower generation and flood control and navigation capacity increase, they can inevitably result in a series of potential environmental (e.g., river flow, water quality, sedimentation), ecological (e.g., ecosystem and biodiversity) and social (e.g., reservoir resettlement and water-related disease) problems from local to basin scale [3], [4].
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