Long-term dramatic spatial and temporal changes in the watershed areas of multiple types of lakes and reservoirs in Xinjiang, China

Abstract

The change of lake and reservoir water area deeply affects regional ecological balance. Under the background of warming and humidification in Xinjiang, it is therefore important to explore such changes for water allocation. Based on Landsat series, Sentinel-2 and MODIS images, this paper studies 12 different types of lakes and reservoirs in Xinjiang, utilized the remote sensing big data platform GEE (Google Earth Engine), the water body index (NDWI, MNDWI, AWEI and MAWEI) is preferably combined with the Otsu threshold method (OSTU) to extract the water body area from 1993 to 2023. It analyzes trends with time series methods, spatial changes via gravity centers & the cell-based flooding frequency method of water bodies. The results show that: (1) The Kappa coefficient of the normalized difference water index (NDWI) to extract the water area is 0.90, and the OA (Overall Accuracy) is 0.95, which is suitable for the extraction of the water area in the arid area; (2) Small lakes and reservoirs show a shrinking area; medium-sized lakes are increasing in area while reservoirs are decreasing; and there are three types of large lakes: shrinking, stabilizing and expanding; (3) The total area of lakes and reservoirs in southern Xinjiang showed a stable increasing trend, and the average coefficient of variation of 0.22 belong to moderate variation intensity. This study reveals the characteristics of long-term spatiotemporal variation characteristics of multiple types of lakes and reservoirs in Xinjiang, which can provide reliable data support for the construction of ecological civilization in the basin.

Keywords

• Arid zones
• Lakes and reservoirs
• Water surface area
• Google Earth Engine
• Spatiotemporal change