# Monitoring Water Area Dynamics in Kashgar (2003-2023) Using Multi-Source Remote Sensing Data
## 1 Introduction
First, seasonal fluctuations in water extent make it challenging to capture the full range of annual variability using a single image acquisition. Determining the optimal acquisition time to meet specific research objectives is also problematic as images acquired during the rainy season will reflect maximum water extent, whereas those acquired during the dry season will primarily depict permanent water bodies. To mitigate this uncertainty, utilizing a full-year time series of imagery is recommended. Second, interannual variability in water area can further complicate trend analysis. Even when using images acquired on the same date across multiple years, accurately capturing long-term trends can be difficult, potentially leading to inconsistencies in both water area and the number of water bodies [14]. Accurately determining the temporal position of a single image within a year, as well as the corresponding temporal position of images acquired on the same date in different years, is crucial for minimizing uncertainty. Therefore, a comprehensive understanding of surface water area dynamics necessitates the analysis of a substantial dataset of remote sensing imagery spanning multiple seasons and years. Rivers and lakes, as vital regional water resources, exhibit high sensitivity to climate change in the Kashgar region. These key geomorphic units play a crucial role in mitigating the impacts of global warming on the region [15]. However, persistent water scarcity has consistently constrained economic and social development in Kashgar, leading to ecosystem fragility [16]. Population growth and economic development have further exacerbated this water shortage issue [17]. Against the backdrop of global warming, changes in water bodies in Kashgar directly reflect the dynamic trends of regional water resources. Despitethe scarcity of long-term studies on water body dynamics in the Kashgar region, accurate quantification of water body area and an understanding of their spatiotemporal variations are crucial. This information is essential for ensuring the sustainable development of the local economy and society, as well as for safeguarding the ecological environment. Given the significance of water resources in the arid region of Kashgar, understanding their spatiotemporal dynamics and the influence of climate change is crucial for predicting future water availability and developing sustainable management strategies. This study leverages the Google Earth Engine (GEE) platform, Landsat and Sentinel-2 satellite imagery, and two water body indices, NDVI and EWI, to delineate water bodies in Kashgar from 2003 to 2023. We employ a random forest algorithm to quantify the total water body area, seasonal variations in water extent, and the area of permanent water bodies. Furthermore, we investigate the influence of precipitation, temperature, and evaporation, as well as regional climatic patterns, on water body area changes. The specific objectives of this study are (1) to characterize the spatiotemporal dynamics of water body area in Kashgar from 2003 to 2023, and (2) to identify the key drivers influencing these changes. Our findings provide valuable insights for policymakers and stakeholders to formulate effective water resource management strategies and promote sustainable development, ultimately contributing to the improvement of the local ecological environment.