# 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  
Figure 2 shows the statistical results of the changes in the water area in Kashgar from 2003 to 2023; the water area in the Kashgar region exhibited a fluctuating downward trend, with an average annual change rate of \(-11.17\) km\({}^{2}\)/year. A detailed analysis is as follows: \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Methods** & **Image** & **OA** & **Kappa** & **CE** & **OE** & **PA** & **UA** \\ \hline \multirow{2}{*}{Mahalanobis Distance} & Sentinel-2 & 78.95\% & 0.7303 & 1.61\% & 39.58\% & 60.42\% & 98.39\% \\  & Landsat 8 & 82.76\% & 0.7816 & 1.18\% & 24.46\% & 75.54\% & 98.82\% \\ \hline \multirow{2}{*}{Minimum Distance} & Sentinel-2 & 61.54\% & 0.5010 & 1.63\% & 30.89\% & 69.11\% & 98.37\% \\  & Landsat 8 & 75.00\% & 0.6889 & 8.72\% & 4.31\% & 95.69\% & 91.28\% \\ \hline \multirow{2}{*}{Maximum Likelihood} & Sentinel-2 & 70.37\% & 0.6333 & 0.73\% & 8.45\% & 91.55\% & 99.27\% \\  & Landsat 8 & 82.86\% & 0.7780 & 0.65\% & 2.85\% & 97.15\% & 99.35\% \\ \hline \multirow{2}{*}{Support Vector Machine} & Sentinel-2 & 81.82\% & 0.7596 & 0.69\% & 0.71\% & 99.29\% & 99.31\% \\  & Landsat 8 & 85.71\% & 0.8149 & 0.36\% & 0.44\% & 99.56\% & 99.64\% \\ \hline \multirow{2}{*}{Random Forest} & Sentinel-2 & 97.10\% & 0.9005 & 0.21\% & 0.41\% & 99.59\% & 99.79\% \\  & Landsat 8 & 95.00\% & 0.9889 & 0.26\% & 0.48\% & 99.52\% & 99.74\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of classification accuracy for five methods applied to two satellite image types in 2023.  
in 2003-2004, water area increased to a maximum of 2924.765 km\({}^{2}\), representing an increase of 576.63 km\({}^{2}\) and a growth rate of 24.72%; in 2004-2016, water area generally decreased, but displayed fluctuating changes, reaching a minimum of 2057.83 km\({}^{2}\) in 2016. The most significant decrease occurred in 2007, with a reduction of 280.42 km\({}^{2}\) and a growth rate of \(-11.55\%\); in 2016-2018, water area increased, with the most substantial increase occurring in 2016, reaching 294.32 km\({}^{2}\) and a growth rate of 14.32%; and in 2018-2023, water area exhibited an overall decrease, characterized by fluctuating changes. The largest decrease occurred in 2019, with a reduction of 211.61 km\({}^{2}\) and a growth rate of \(-8.5\%\). To characterize the temporal trends in water area changes within the Kashgar region, this study employed [PERSON]'s slope estimator, the Mann-Kendall (MK) test, and change point analysis. The analysis of the time series of water area change in the Kashgar region from 2003 to 2023 revealed a Sen's slope estimate of \(-0.52\), indicating an overall downward trend. The significance of this trend was assessed using the Mann-Kendall (MK) test. As shown in Figure 3, the estimated Sen's slope for water area changes in the Kashgar region passed the 0.95 confidence level, confirming the statistical significance of the decreasing trend. The change point analysis identified a shift in water area in 2011, with a significant decrease observed in that year. A consistent upward trend was evident from 2003 to 2010, followed by a sustained downward trend from 2012 to 2023. Utilizing the water inundation frequency method and interannual water area statistics for the Kashgar region, this study characterized the interannual distribution of permanent  
Figure 3: Mann–Kendall test for water area changes in the Kashgar region (2003–2023). Figure 2: Temporal trends in water area within the Kashgar region. and seasonal water bodies. From 2003 to 2023, the overall trend of seasonal water area changes mirrored the trend of total water area changes, exhibiting a fluctuating downward trend with an average annual change rate of \(-12.80\) km\({}^{2}\)/year. As depicted in Figure 4a, the seasonal water body area increased by \(290.142\) km\({}^{2}\) between 2003 and 2004, representing a growth rate of \(21.70\%\), reaching a maximum of \(1627.339\) km\({}^{2}\) in 2004.