Abstract: Under the context of water shortage in China, it is important to rationally plan agricultural soil and water resources. To realize the extraction of regional crop planting structure and analyze the spatial-temporal variations of crop water demand, this study took the Old Wanfu River Basin, an important agricultural area in Jining City, Shandong Province, as the study area. NDVI time series of crop growth period were constructed based on Landsat-8 image, combined with GF-2 image, field survey data, and crop phenology. The decision tree method was used to extract crop planting structure. Furthermore, the single crop coefficient method was used to calculate crop water demand, combined with the Penman-Monteith formula and GIS spatial analysis function. Results showed that the average error of wheat-rice extraction using decision tree method was the smallest (13.5%), and the average error of vegetable extraction was the largest (23.0%). The wheat-rice rotation pattern was distributed in the eastern part of the basin, wheat-corn rotation pattern mainly distributed in the western part of the basin, and vegetables mainly distributed in the middle and west of the basin. There were significant differences in the annual spatial and temporal distribution of crop water demands. On the temporal scale, water demand of winter crops was significantly lower than that of other seasons, water demand of summer crops was the largest, and spring and summer crops accounted for about 70% of the annual crop water demand. On the spatial scale, crop water demand in the eastern rice-growing area was significantly higher than that in other areas. The water demand of the same planting pattern was different in different planting areas. The annual water demand of wheat-corn ranged from 915.6 mm to 952.9 mm, and the difference between different areas was 37.3 mm. There were significant differences in water demands of rice, corn, vegetables, and wheat during the growth period, being 846.87, 561.7, 519.37, and 415.24 mm, respectively. Furthermore, crop water demand reached its peak at the jointing booting (bolting) stage. The results indicated the method by combining NDVI time series, generated with on Landsat-8 and GF-2 image data, and decision tree classification could realize the extraction of regional crop planting structure. This study could provide a scientific basis for the formulation of local irrigation system and the optimization management and allocation of agricultural soil and water resources.

Key words: crop evapotranspiration, the Old Wanfu River Basin, NDVI, single crop coefficient method, spatial-temporal characteristics