## 5 Conclusions  
Based on the findings of this study, we conclude the following: First, elevated multi-year average values of the cropland CUE and WUE\({}_{\text{NPP}}\) are mainly concentrated in western Henan Province, whereas higher WUE\({}_{\text{GPP}}\) values are primarily found in the central and southwestern regions; the proportion of cropland exhibiting declining trends in the CUE, WUE\({}_{\text{NPP}}\), and WUE\({}_{\text{GPP}}\) accounted for 78.26%, 82.13%, and 76.77% in the overall cropland area, with annual decreases of 0.0017 a\({}^{-1}\), 0.009 g C m\({}^{-2}\) mm\({}^{-1}\)a\({}^{-1}\), and 0.01 g C m\({}^{-2}\) mm\({}^{-1}\)a\({}^{-1}\), respectively. Second, non-irrigated cropland consistently exhibited higher CWUE values compared to irrigated cropland. The multi-year average values of the irrigated cropland WUE\({}_{\text{GPP}}\), WUE\({}_{\text{NPP}}\), and CUE were 2.51 g C m\({}^{-2}\) mm\({}^{-1}\), 1.08 g C m\({}^{-2}\) mm\({}^{-1}\), and 0.43, respectively. Third, sunlight emerged as the primary driver of the irrigated cropland WUE\({}_{\text{GPP}}\), while precipitation played a major role in influencing the WUE\({}_{\text{NPP}}\) and irrigated cropland CUE. In contrast, the GDP has the least effect on irrigated cropland CWUE. Finally, as the LAI and precipitation increased, SHAP values for irrigated cropland CUE declined from positive peaks to zero and then to negative minima, indicating a transition from weakening positive effects to strengthening negative impacts.  
This study revealed the spatiotemporal dynamics of cropland CWUE in Henan Province, offering a scientific basis for regional agricultural optimization. It is recommended to establish ecological agricultural reserves in the high-value western regions to sustain efficient water use while promoting drip irrigation in the central-eastern low-value areas to counter the observed annual decline in the WUE\({}_{\text{GPP}}\) (0.01 g C m\({}^{-2}\) mm\({}^{-1}\)a\({}^{-1}\)). CWUE was found to be significantly higher in non-irrigated cropland compared to irrigated areas, suggesting the potential value of piloting a hybrid model that combines rainfed dry farming with precision supplemental irrigation. These findings provide practical sup port for the development of a 5 million mu water-saving irrigation demonstration zone in the Yellow River Basin, contributing to food security and resource conservation. Future research will focus on constructing a multi-scale technical system by integrating Sentinel-6 data with optimized XGBoost modeling, aiming to develop a meter-scale cropland CWUE assessment framework that offers precise guidance for advancing water-efficient agricultural technologies.  
Conceptualization, G.L.; Data curation, Y.C.; Formal analysis, G.L., F.Y. and L.H.; Funding acquisition, G.L. and F.Y.; Methodology, G.L., Z.Y., L.H. and Y.L.; Resources, Z.Y.; Validation, T.Q., Y.L. and K.Z.; Visualization, H.G.; Writing--original draft, G.L., Z.Y., T.Q. and Y.C.; Writing--review and editing, H.G., Y.L. and K.Z. All authors have read and agreed to the published version of the manuscript.  
This research has gained substantial support from the Postdoctoral Fellowship Program of CPSF (GZC20230732), the Major Science and Technology Projects in Gansu Province (24 ZDGE002), and the Science and Technology Research Projects in Henan Province (242102321167, 252102320300).  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.