## 4 Results and Discussion
### Effect of LILC Change on Water Yield  
Simple linear regression analysis was applied to identify the effect of LULC change on water yield (see Appendix A for input data in Table A3). The simple linear equations between water yield and specific dominant LULC types under dry and wet scenarios are displayed in Figures 12 and 13. The results show that annual water yield in the dry and wet year scenarios is positively correlated with urban and built-up areas, with R\({}^{2}\) values of 0.91 and 0.92, respectively (Figures 12a and 13a). This finding indicates that when urban and built-up areas increase, water yield increases. This phenomenon is expected because surface runoff, as a significant hydrologic component of water yield, will increase when urban and built-up areas with impervious surfaces increase. Likewise, annual water yield in both scenarios is positively correlated with idle land (abandoned and fallowed fields), with R\({}^{2}\) values of 0.91 and 0.93, respectively (Figures 12b and 13b). This finding shows that when idle land increases, water yield increases. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multicolumn{8}{c}{**Hydrological Component (mm)**} \\ \cline{2-9}  & **Surface Runoff** & **Lateral Flow** & \begin{tabular}{c} **Groundwater** \\ **(Shallow Aquifer)** \\ \end{tabular} & \
\begin{tabular}{c} **Groundwater** \\ **(Deep Aquifer)** \\ \end{tabular} &
\begin{tabular}{c} **Evapotranspiration** \\ \end{tabular} & **Water Yield** \\ \hline
2020 & 1264.17 & 147.02 & 882.84 & 53.39 & 935.00 & 2347.42 \\
2021 & 1269.98 & 146.04 & 880.12 & 53.22 & 934.80 & 2349.36 \\
2022 & 1275.22 & 145.45 & 877.16 & 53.06 & 934.50 & 2350.89 \\
2023 & 1287.41 & 147.66 & 865.83 & 52.43 & 936.10 & 2353.33 \\
2024 & 1294.66 & 143.86 & 863.70 & 52.31 & 935.50 & 2354.53 \\
2025 & 1313.41 & 141.63 & 852.02 & 51.67 & 935.60 & 2358.73 \\
2026 & 1397.25 & 134.91 & 791.27 & 48.60 & 936.00 & 2372.03 \\
2027 & 1417.47 & 132.88 & 777.66 & 47.84 & 935.40 & 2375.84 \\
2028 & 1424.99 & 132.35 & 772.17 & 47.56 & 935.50 & 2377.06 \\
2029 & 1439.43 & 129.48 & 763.20 & 47.12 & 934.30 & 2379.23 \\ \hline Average & 1338.40 & 140.13 & 832.60 & 50.72 & 935.27 & 2361.84 \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Annual water yield of Phuket Island between 2020 and 2029 under the wet year scenario. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Month**} & \multicolumn{8}{c}{**Water Yield between 2020 and 2029 (Million m\({}^{3}\))**} & \multirow{2}{*}{**Average**} \\ \cline{2-9}  & **2020** & **2021** & **2022** & **2023** & **2024** & **2025** & **2026** & **2027** & **2028** & **2029** \\ \hline January & 44.38 & 44.50 & 44.66 & 44.89 & 45.05 & 45.34 & 45.87 & 45.96 & 46.09 & 46.32 & 45.31 \\ February & 20.02 & 19.96 & 19.88 & 19.69 & 19.60 & 19.38 & 19.22 & 19.07 & 18.98 & 18.83 & 19.46 \\ March  
Figure 12: Simple linear regression analysis between LULC type and water yield under dry year scenario. Figure 13: Simple linear regression analysis between LULC type and water yield under wet year scenario. On the contrary, annual water yield in the dry and wet year scenarios has a high negative correlation with perennial trees and orchards, with R2 values of 0.91 and 0.92, respectively (Figures 12c and 13c). This finding indicates that when perennial trees and orchards increase, water yield decreases. This phenomenon is expected because surface runoff will decrease when areas are covered by vegetation. Likewise, annual water yield in both scenarios shows a high negative correlation with evergreen forest, with R2 values of 0.91 and 0.92, respectively (Figures 12d and 13d). This finding confirms the influence of LULC change on the surface runoff in the watershed. These findings are comparable to those of other studies. To determine the impact of land-use change on surface runoff in Huay Tung Lung Watershed of Mun Basin, [PERSON] and [PERSON] applied the SWAT model to estimate surface runoff and the CA Markov model to predict land-use changes.