Assessment of water-saving potential in paddy irrigation system under varying hydrological conditions based on modified SWAT model

Effective water management in paddy irrigation areas is complicated by the dynamic influences of precipitation, surface heterogeneity, and agricultural practices. To address these challenges, this study introduces an innovative dynamic irrigation decision module that synergistically integrates real-time soil moisture thresholds with future precipitation forecasts, overcoming the passive limitations of traditional water management models in responding to environmental variability. This module is incorporated into the SWAT model to develop a comprehensive dynamic assessment framework focusing on the interrelations within the "field-channel-pond" cascading system, thereby enhancing the overall comprehensiveness and flexibility of water management strategies. The results indicate that this framework is effective in managing the variability of precipitation and soil moisture regulation under dynamic climatic conditions, revealing significant interannual variability in paddy field water balance components that informs water resource allocation. Subsequently, water-saving scenarios were established for each component of the "field-channel-pond." Among the various strategies, field management exhibited the highest water-saving potential, with a multi-year average saving rate of 33.0%, significantly outperforming channel system renovations (4.3%) and pond modifications (5.2%). The effectiveness of field and pond measures diminished during drier years, while enhancing channel conveyance efficiency became increasingly critical as rainfall decreased. This study provides a robust and scientifically validated tool for the quantitative evaluation and optimization of water management strategies in complex irrigation systems under variable climatic conditions.