# Monitoring Water Area Dynamics in Kashgar (2003-2023) Using Multi-Source Remote Sensing Data
## 3 Results and Analysis
### Temporal Characteristics of Annual Water Area Changes in the Kashgar Region
Subsequently, the seasonal water body area fluctuated and decreased, reaching a minimum of \(1081.229\) km\({}^{2}\) in 2023. The largest area change occurred in 2010, with a decrease of \(407.163\) km\({}^{2}\) and a growth rate of \(-26.08\%\). In contrast, the permanent water body area in the Kashgar region generally exhibited a fluctuating upward trend, with an average annual change rate of \(2.28\) km\({}^{2}\)/year. From 2003 to 2004, the permanent water body area increased by \(289.486\) km\({}^{2}\), representing a growth rate of \(28.72\%\), reaching a maximum of \(1297.426\) km\({}^{2}\) in 2004. From 2004 to 2022, the permanent water body area fluctuated and decreased, reaching a minimum of \(855.972\) km\({}^{2}\) in 2022. The largest area change occurred in 2008, with an increase of \(185.890\) km\({}^{2}\) and a growth rate of \(18.17\%\). Between 2022 and 2023, the permanent water body area increased by \(225.257\) km\({}^{2}\), representing a growth rate of \(26.32\%\). The comparison of changes in permanent and seasonal water areas with total water area and the proportion of seasonal water bodies (Figure 4a,b) reveals that seasonal water area in Kashgar constitutes \(50\)-\(60\%\) of the total water area, reaching a minimum of \(49.86\%\) in 2007. Considering the characteristics of water area fluctuations, overall water area changes in Kashgar are driven by variations in both permanent and seasonal water areas, with the contribution of seasonal water area changes slightly exceeding that of permanent water area changes. Figure 4: (**a**) Interannual variability of permanent and seasonal water bodies in the Kashgar region, (**b**) seasonal water body proportion in the Kashgar region, (**c**) Mann–Kendall Test for trends in permanent water area in the Kashgar region (2003–2023), (**d**) Mann–Kendall test for trends in seasonal water area in the Kashgar region (2003–2023). To characterize the trends in the permanent and seasonal water body area changes within the Kashgar region, this study employed Sen's slope estimation, the Mann-Kendall (MK) test, and change point analysis. The Sen's slope estimate for the permanent water body area changes from 2003 to 2023 was 0.42, indicating a slight overall upward trend. Conversely, the Sen's slope estimate for the seasonal water body area changes was \(-0.16\), suggesting a slight downward trend. To assess the significance of these trends, the MK test was applied (Figure 4c,d). The Sen's slope estimates for the permanent water body area changes passed the 0.95 confidence level, confirming the statistical significance of the increasing trend. No distinct change points were identified for the permanent water body area, failing the 0.95 confidence test only in 2013. From 2003 to 2013, the permanent water body area exhibited a significant downward trend, while from 2013 to 2023, a significant upward trend was observed. The Sen's slope estimate for the seasonal water body area changes did not pass the 0.95 confidence test, indicating a non-significant decreasing trend. A change point was identified in 2006, with a significant decrease in the seasonal water body area. From 2003 to 2006, the seasonal water body area displayed a stable upward trend, followed by a stable downward trend from 2006 to 2023. To validate the experimental findings, the upper reaches of the Yarkand River, a representative water body in the Kashgar region, were selected as the validation site. Situated in the high-altitude mountainous terrain west of Kashgar, this area receives the majority of the river's recharge, making it an ideal location for result verification. The water level data for the upper Yarkand River from 2003 to 2023 were obtained from the Kuruklangan (III) hydrological station, located in Datong Township, Taxkorgan County. As illustrated in Figure 5, the water level data from this station exhibits a strong correlation with the temporal trends in water body area change observed across Kashgar.