Impact of ecological water supplementation on vegetation changes in the Hotan River Basin as judged by multi-source remote sensing data

Vegetation and water body affect terrestrial ecosystem．The Hotan River Basin reaches deep into the hinterland, but water resources are insufficient．Runoff of the Hotan River has decreased in recent years, bringing huge challenges to the growth of Populus euphratica forests in the Hotan Oasis and coastal areas．To alleviate this situation, Hotan Administration Bureau carried out ecological emergency water supplementation to the Populus euphratica forest in Akjak and Postan ranch on July 9, 2017．To assess impact of ecological water transportation measures on ecological environment in the Hotan River Basin in 2017, Landsat remote sensing images and MODIS datasets were used to examine spatial and temporal distribution of river water area and vegetation coverage in the desert section of the Hotan River Basin．Seasonal variation characteristics of NDVI values and landscape metrics of vegetation and water body were analyzed to study the spatial variations of the ecological environment．The ecological water supplementation measures were found to have increased water and vegetation area over the basin and alleviated ecological environment．After ecological water supplementation, river meandering coefficient decreased, average water surface width increased, the river gradually developed in the direction of flat flow．Spatial distribution of NDVI showed characteristics of high vegetation coverage at both ends of the river but low coverage in the middle of the river．Landscape metrics revealed aggregation of water landscape and vegetation landscape in the desert section of Hotan River Basin, to effectively alleviate the worsened ecological environment．