Irrigation water constitutes a significant proportion of human water consumption. Incorporating temporal patterns of irrigation water use into distributed dual water cycle models for river basins is critical for advancing water resources management. However, existing modeling frameworks often neglect the impacts of irrigation water use chronology on simulation accuracy. This study developed a regional irrigation water use model based on the crop coefficient method and field water balance principles, accounting for the planting structures of major crops across sub-regions. The model was integrated with the distributed dual water cycle model WEP-L to simulate hydrological processes in the Poyang Lake Basin. Key findings include: (1) Agricultural irrigation water use in the Poyang Lake Basin predominantly occurs from May to October, peaking from July to September (>25% monthly contribution). (2) The enhanced model demonstrates superior performance, with Nash-Sutcliffe Efficiency (NSE) exceeding 0.8 and relative error (RE) within ±5% for monthly streamflow simulations at seven hydrological stations during the 1980–2021 calibration/validation periods.(3) Compared to conventional models ignoring irrigation chronology, the proposed method significantly improves simulation accuracy, particularly in drought years. During major irrigation seasons of dry years (P >75%), the NSE increased by over 0.09 and |RE| decreased by 5.3% on average across representative stations. Among the five major sub-basins (Gan, Fu, Xin, Rao, and Xiu Rivers), the Rao and Xiu River basins exhibited the most significant improvements. This study demonstrates the necessity of integrating irrigation water use temporal patterns into basin-scale water cycle simulations.