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Autumn irrigation is a key agricultural practice during the non-growing season in the Hetao Irrigation District, and its spatial distribution and dynamic monitoring are essen-tial for refined water resource management and for salinity control. Taking the Yichang Irrigation District in Hetao as the study area, this study integrated multi-source optical remote sensing data from GF-1/GF-6, HJ-2A/B, Landsat 8/9, and Sentinel-2, acquired dur-ing the autumn irrigation period (October–November 2024). The spectral characteristics of croplands in the non-growing season were analyzed, and a soil moisture index was con-structed to retrieve the extent of autumn irrigation and reveal its spatiotemporal evolution at both the district and irrigation unit scales. The results indicate that cropland spectral responses in the non-growing season can be classified into three types: non-irrigated fields, post-irrigation fields with a surface-water layer, and post-irrigation fields after sur-face-water infiltration. The visible–red-edge–near-infrared (450–890 nm) and shortwave infrared (1565–2290 nm) regions are highly sensitive to soil moisture variations. Among the tested indices, the soil moisture index based on the near-infrared–shortwave infrared band combination exhibited the most consistent performance and highest accuracy in identifying irrigated areas. Newly irrigated areas characterized the irrigation rate, whereas the cumulative irrigated area reflected the actual coverage. Together, these indi-cators delineate the four phases of autumn irrigation: initiation, acceleration, stabilization, and termination. The coefficient of determination (R²) between the remotely sensed cumu-lative irrigated area and statistical records was 0.95. The final cumulative au-tumn-irrigated area was 1040.76 km², compared with 831.4 km² reported in the statistical data, satisfying the accuracy requirement for large-scale irrigation monitoring. At the irri-gation-unit scale, the linear fit for the newly irrigated area yielded R² = 0.75, effectively capturing incremental changes across different phases. The spatiotemporal evolution ex-hibited clear regularity. Temporally, the entire district follows a four-phase pattern, and the similarity between unit- and district-scale processes increases with the ca-nal-controlled area. Spatially, early stage irrigation was concentrated along the Fengji, Shahe, Yihe, and Tongji main canals, forming an east–west gradient with greater intensity in the east. As irrigation progresses, irrigated areas expand along the hierarchy of the main, primary, branch, and lateral canals, gradually forming contiguous patches and ul-timately an integrated district-wide pattern. Irrigation remains relatively sparse along the northern margin and in the southwest, whereas large canal units, such as Fengji, Zaohuo, Tongji, and Yihe, dominate the spatial evolution. This multi-source remote sensing ap-proach provides a scientific basis for optimizing autumn irrigation water allocation, im-proving irrigation scheduling, and enhancing water-use efficiency in the Hetao Irrigation District.