## 1 Introduction  
In the context of global climate change and increasing water scarcity [1], food security poses a major challenge worldwide. Water resources are widely recognized as a key factor for ensuring food security and the sustainable development of regional agricultural production [2; 3]. The development of irrigated agriculture is essential to increase the regional food output and secure food supplies [4; 5; 6]. Climate change exacerbates water stress, inevitably impacting water availability for agriculture, particularly irrigated farming, thereby constraining and threatening food production [7; 8]. As the world's largest food producer and consumer, China depends heavily on the health of its agricultural ecosystems [9]. Henan Province, a major agricultural region with extensive arable land and a favorable climate, serves as a critical production base for China's staple grains [10], making its cropland ecosystems vital to national food security [11]. Croplands play a dual role: they are essential for food production and act as climate regulators. Agricultural soils represent significant global carbon reservoirs, while cropland vegetation generates an \"oasis effect\" that moderates the surface temperature, humidity, and energy balance [12; 13]. Conversely, agricultural activities are major sources of greenhouse gases, such as methane (CH\({}_{4}\)) and nitrous oxide (N\({}_{2}\)O) [14]. To sustain healthy agroecosystems that balance these functions amid climate change and unsustainable irrigation practices, robust metrics are required to quantify productivity and water use efficiency. A core indicator, carbon water use efficiency (CWUE), describes the ability of terrestrial ecosystems to optimize carbon uptake and water use synergistically [15]. Essentially, it measures how efficiently an ecosystem uses water to capture and store carbon dioxide. CWUE primarily encompasses water use efficiency (WUE) and carbon use efficiency (CUE). WUE includes two key components: the WUE\({}_{\text{GPP}}\) and WUE\({}_{\text{NPP}}\)[16; 17]. The WUE\({}_{\text{GPP}}\), defined as the gross primary productivity (GPP) divided by evapotranspiration (ET) [18], serves as a critical indicator for assessing carbon sequestration relative to water consumption in terrestrial ecosystems [19].The WUE\({}_{\text{NPP}}\), calculated as the net primary productivity (NPP) divided by ET, is a vital physiological indicator linking the carbon and water cycles and provides an important basis for evaluating ecosystem responses to climate change [20]. CUE measures the efficiency with which an ecosystem converts total captured carbon (GPP) into net carbon stored as biomass (NPP), after accounting for the carbon lost through plant respiration [21]. This ratio offers valuable insight into ecosystem carbon management, influencing both internal processes and the global carbon cycle [22; 23; 24]. Recent studies leveraging satellite remote sensing have significantly advanced the understanding of the spatiotemporal variability of ecosystem CWUE and its coupled processes [18; 25; 26]. The sensitivity of different CWUE indicators to environmental factors varies substantially across ecosystems. The global terrestrial vegetation CUE increased significantly from 2000 to 2018, although localized declines occurred in regions such as the Amazon and northeastern India [27]. The ecosystem WUE\({}_{\text{GPP}}\) exhibits a latitudinal gradient, increasing toward lower latitudes [28; 29]. In natural and urban plantation forests, the GPP and CUE strongly respond to temperature and humidity [30], while changes in the WUE\({}_{\text{NPP}}\) in North China's mountain ecosystems are primarily driven by combined effects of the leaf area index (LAI), temperature, and precipitation [19; 31]. Although these ecosystem-level studies offer fundamental insights into the spatiotemporal variability and its drivers, agricultural systems require specialized research frameworks owing to their unique carbon-water dynamics and intensive human impacts.