## 3 Results
### Spatial Drivers and Synergistic Mechanisms of Irrigated Cropland CWUE  
#### 3.3.1 Spatial Distribution of SHAP Values of Driving Factors and Irrigated Cropland CWUE  
The spatial distribution of SHAP values of drivers and irrigated cropland CWUE in Henan Province is illustrated in Figure 9. The statistical table of SHAP values for the influence of driving factors on CWUE in irrigated cropland is shown in Table 4. The positive effects of the GDP and photosynthetically active radiation absorption ratio on changes in the irrigated cropland \(\mathrm{WUE_{NPP}}\) accounted for 60.63% and 60.72% of the area, respectively, predominantly in northwestern Henan. Temperature had a negative impact on the \(\mathrm{WUE_{NPP}}\) over 51.53% of the area, mainly in the northern region, with the spatial influence of the LAI on the \(\mathrm{WUE_{NPP}}\) showing a similar pattern. In central and northern Henan, temperature generally exerted negative effects on the \(\mathrm{WUE_{GFP}}\), while other drivers had mostly positive impacts. Specifically, the positive influence of the LAI and GDP on the irrigated cropland \(\mathrm{WUE_{GFP}}\) accounted for 62.52% and 55.77% of the area, respectively. Additionally, the photosynthetically active radiation absorption ratio data positively affected the \(\mathrm{WUE_{GFP}}\) across approximately 61.20% of the irrigated cropland, with the strongest effects in the northern part of the province. For CUE, positive effects of the temperature, sunlight, GDP, and photosynthetically active radiation absorption ratio covered about 53.11%, 53.46%, 56.31%, and 57.62% of the irrigated cropland area, respectively, largely concentrated in northern Henan. Figure 8: Quantitative evaluation of GPP, NPP, and ET of irrigated and non-irrigated cropland in Henan Province, 2001–2019. Figure 9: Spatial distribution of SHAP values of drivers and CWUE of irrigated cropland in Henan Province: (**a1**–**a6**) WUE\({}_{\rm NP}\), (**b1**–**b6**) WUE\({}_{\rm GPP}\), and (**c1**–**c6**) CUE, with respect to Tem, Sun, Pre, LAI, GDP, and Rad. The SHAP summary of the drivers of irrigated cropland versus CWUE in Henan Province from 2001 to 2019, along with the relative importance of each driver, is presented in Figure 10. Sunlight was identified as the primary determinant of the WUE\({}_{\text{GPP}}\) in irrigated cropland, while precipitation played a secondary yet significant role in modulating this relationship (Figure 10(a1,a2)). Precipitation emerged as the dominant driver for the WUE\({}_{\text{NPP}}\) and CUE, with sunlight and the LAI serving as secondary determinants for the WUE\({}_{\text{NPP}}\) and CUE, respectively. In irrigated cropland, a larger SHAP value magnitude corresponds to a stronger influence on CWUE. Among all factors, precipitation had the greatest impact on CWUE, whereas the GDP had the least influence on the irrigated cropland CWUE. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Impact Factor** & **Impact** & **WUE\({}_{\text{NPP}}\)** & **WUE\({}_{\text{GPP}}\)** & **CUE** \\ \hline \multirow{2}{*}{Tem} & Positive & 48.47\% & 44.69\% & 53.11\% \\  & Negative & 51.53\% & 55.31\% & 46.89\% \\ \hline \multirow{2}{*}{SUN} & Positive & 45.83\% & 51.23\% & 53.46\% \\  & Negative & 54.17\% & 48.77\% & 46.54\% \\ \hline \multirow{2}{*}{Pre} & Positive & 49.99\% & 58.67\% & 49.70\% \\  & Negative & 50.01\% & 41.33\% & 50.30\% \\ \hline \multirow{2}{*}{LAI} & Positive & 56.89\% & 62.52\% & 50.54\% \\  & Negative & 43.11\% & 37.48\% & 49.46\% \\ \hline \multirow{2}{*}{GDP} & Positive & 60.63\% & 55.77\% & 56.31\% \\  & Negative & 39.37\% & 44.23\% & 43.69\% \\ \hline \multirow{2}{*}{Rad} & Positive & 60.72\% & 61.20\% & 57.62\% \\  & Negative & 39.28\% & 38.80\% & 42.38\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The statistical table of SHAP values for the influence of driving factors on the irrigated cropland CWUE. Figure 10: The SHAP summary of drivers of irrigated cropland versus CWUE and relative importance plots for each feature in Henan Province, 2001 to 2019.