Application of Landsat derived indices and hydrological alteration matrices to quantify the response of floodplain wetlands to river hydrology in arid regions based on different dam operation strategies

The response of floodplain wetlands to changes in river hydrology caused by different dam operation strategies in arid regions has attracted worldwide attention in recent decades. However, less is known about quantifying the effects of dam operations on wetlands in different lateral zones located in low-gradient floodplains in arid regions using remote sensing and hydrological time series. In this study, hydrological time series from 1975 to 1985 and 2008-2014 were used to quantify 67 flow metrics during different dam operation periods. Time series of remote sensing data (39 periods in total) from 1975 to 1977 and 2008-2014 were analysed to quantify the spatiotemporal dynamics in floodplain wetland types (river, bare wet land and wetland vegetation areas). In addition, a correlation analysis was performed to quantify the relationship between each wetland type and the flow metrics in different lateral zones. The results indicate that approximately 90% of the water and bare wet land area were located in the continuously and frequently inundated zones. Vegetation was the main wetland type in the regularly and extremely rarely inundated zones, and a 45.7% decrease in the vegetation area of these two belts occurred; in contrast, a 20.14 km(2) of increase in vegetation occurred in the frequently inundated zone after the uniform scheduling was implemented for the entire river. Linear correlation and regression analysis showed that the different dam operation strategies resulted in various wetland changes in the different lateral zones. The decrease in high flows and increase in low flows caused a decrease in the vegetation cover area in the regularly and extremely rarely inundated zones and led to vegetation encroachment in the frequently inundated zone. Our study can improve the management of wetlands and water resources in arid region floodplains. (C) 2019 Elsevier B.V. All rights reserved.