Irrigation water demand patterns and driving factors for ratooned rice before starting irrigation and after stopping irrigation in the Pi-Shi-Hang Irrigation District
To reveal the spatial and temporal variations and driving factors of irrigation water requirements for ratoon rice before starting irrigation and after stopping irrigation in an irrigation district,the Mann-Kendall method was used to study the changes in irrigation water requirements for ratoon rice before starting irrigation and after stopping irrigation in three sub-irrigation areas of the Pi-Shi-Hang Irrigation District from 1958 to 2022. Additionally,multiple linear regression and pearson correlation analysis methods were employed to further examine the relative contributions of major meteorological factors,including reference crop evapotranspiration and rainfall,to irrigation water requirements. The results of the study showed that the irrigation water requirements for regenerated rice in Pihe Irrigation District(PID),Shihe Irrigation District(SID),and Hangbuhe Irrigation District (HID) before starting irrigation was significant differences due to the different start dates,with values of 126.6,108.5 and 93.2 mm,respectively,and showed a significant upward trend at PID and SID,with rates of 0.55 and 0.29 mm/a,while HID changing trends were not significant. After stopping irrigation the irrigation water requirements for regenerated rice in the PID,SID and HID from 1958 to 2022 were 58.0,55.1 and 54.0 mm,respectively,and their changing trends were not significant. The contribution rate of ET 0 to the irrigation water demand of regenerated rice exceeded 70％. ET 0 is the main factor affecting the irrigation water demand of regenerated rice. Relative humidity and sunshine hours are the two main meteorological factors affecting the irrigation water demand of regenerated rice before starting irrigation and after stopping irrigation in the Pi-Shi-Hang Irrigation District.
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