## 3 Results
### Spatial Variation Trends of SPEI  
The spatial distribution of annual and seasonal SPEI trends from 2000 to 2018 is illustrated in Figure 5. In spring (Figure 5a,a'), the eastern regions predominantly exhibited a wetting trend, while the western areas mainly showed drying. Slightly drying zones covered 52% of the area, with slightly wetting zones accounting for 45%.  
During summer (Figure 5b,b'), most regions, except for parts of the west, displayed a wetting trend, particularly pronounced in the east. Drying zones comprised 21% of the area, whereas slight wetting zones dominated at 58%. Autumn saw a significant increase in SPEI across most areas, with drying zones covering less than 1% (Figure 5c,c'). Slightly wetting zones made up 44% of the area, and significant wetting zones accounted for 56%. Winter trends contrasted with this (Figure 5d,d'), with most regions experiencing drying, especially in the southwest and southeast, while the central areas showed slight wetting. Drying zones covered 49% of the area, with slight wetting zones at 48%. Overall, the annual SPEI trends indicated a predominant wetting trend across the basin (Figure 5e,e'), most notably in the eastern regions, with minor drying trends in the west. Wetting zones covered 90% of the area, including 64% slight wetting and 26% significant wetting zones.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Annual** & **Spring** & **Summer** & **Autumn** & **Winter** \\ \hline Sen slope & & & & & \\ (/a) & 0.02742 & 0.01344 & 0.04575 & 0.07995 * & \(-\)0.00591 \\ MK test & 1.53936 & 0.20991 & 1.32945 & 2.37902 & \(-\)0.06997 \\ \hline \hline \end{tabular} Note: * means that it passed the significance level test of 0.05.  
\end{table}
Table 3: Significance level of annual and seasonal SPEI variations.  
Figure 4: Annual and seasonal variation characteristics of SPEI values and MK values. Note: **(a)** spring variations of SPEI values; **(a\({}^{\prime}\))** spring variations of MK values; **(b)** summer variations of SPEI values; **(b\({}^{\prime}\))** summer variations of MK values; **(c)** autumn variations of SPEI values; **(c\({}^{\prime}\))** autumn variations of MK values; **(d)** winter variations of SPEI values; **(d\({}^{\prime}\))** winter variations of MK values; **(e)** annual variations of SPEI values; **(e\({}^{\prime}\))** annual variations of MK values.  
Figure 5: Spatial distribution of annual and seasonal SPEI variations. Note: (**a**) spatial distribution of spring SPEI variations for vegetation according to slope; (**a**) spatial distribution of spring SPEI  
variations for vegetation according to significance; (**b**) spatial distribution of summer SPEI variations for vegetation according to slope; (**b**') spatial distribution of summer SPEI variations for vegetation according to significance; (**c**) spatial distribution of autumn SPEI variations for vegetation according to slope; (**c**') spatial distribution of autumn SPEI variations for vegetation according to significance; (**d**) spatial distribution of winter SPEI variations for vegetation according to slope; (**d**') spatial distribution of winter SPEI variations for vegetation according to significance; (**e**) spatial distribution of annual SPEI variations for vegetation according to slope; (**e**') spatial distribution of annual SPEI variations for vegetation according to significance.  
In summary, the SPEI trends in the West Liao River Basin from 2000 to 2018 exhibited significant seasonal and regional variations, with an overall wetting trend, though drying persisted in western regions and during winter.