Assessing the effects of controlled drainage on regional hydrological cycle and crop waterlogging and drought based on a coupled agro-hydrological model

Controlled drainage (CD) is an effective practice for mitigating both waterlogging and drought by regulating surface water and groundwater. However, most existing studies focus on its field-scale effects, while regional impacts of CD on coupled hydrological and crop growth processes and quantitative management strategies remain insufficiently explored. To address this gap, we developed a coupled agro-hydrological model integrating surface water, groundwater and crop growth processes. The model was calibrated and validated against ditch water levels, groundwater levels, and crop yields, demonstrating good agreement with observations. Global sensitivity and uncertainty analysis using the extended Fourier amplitude sensitivity test method identified soil porosity (n) and the van Genuchten parameter (α) in the 0–0.2 m soil layer as the most influential parameters. Results show that precipitation determines the dominant water stress, and also suitability and appropriate schemes of CD. Waterlogging is the primary water stress for maize, particularly during the jointing-tasseling stage, whereas drought mainly affects wheat, particularly during the heading-milk maturity stage. CD significantly influences groundwater table depth (GWT) and groundwater-to-soil recharge (GtoS), thereby altering crop water stress and yields. Strong negative linear relationships were observed between net GtoS and GWT (|R|>0.9), and between crop yields and GWT (|R|>0.84). CD effects are amplified when precipitation deviates from critical thresholds, marking transition between drought- and waterlogging-dominated regimes. Overall, this study provides a process-based framework for regional assessment of CD, offering precipitation-specific management schemes to balance water supply and stress, thereby supporting sustainable water governance and crop production.