Impacts of the channel/barrier effect and three-dimensional climate-A case study of rice water requirement and irrigation quota in Yunnan, China

Yunnan is a large rice-growing province in China that is situated in a low-latitude plateau area. In this province, the channel/barrier effect and three-dimensional climate play prominent roles and significantly influence the rice water requirement (ETc) and irrigation quota (IQ), while the research about the influence mechanism and results is lacking. We estimated the rice ETc and IQ of different hydrological years based on the experimental data from six areas of mid-season rice and the single crop efficient approach recommended by FAO-56. The contour maps were drawn with GIS, and the spatial distribution of the rice ETc and IQ under the influence of the channel/barrier effect and three-dimensional climate were analyzed. The results showed that high water ETc and IQ of rice were distributed in the hot, dry river valley area. The rice ETc was the smallest in northwestern Yunnan, and the IQ was the smallest in southern Yunnan. The ETc and IQ of rice were divided into several intervals by mountains and valleys, and varied largely among different channels and little within one channel. The three-dimensional climate results in the abrupt changes of ETc and IQ, The leading meteorological factors causing the abrupt changes were different, and there were also complex correlations between these meteorological factors. Taken together, temperature and rainfall were the most critical elements in the three-dimensional climate. The results of this study illustrated the regularity and inherent mechanism of the rice ETc and IQ under the influences of the channel/barrier effect and three-dimensional climate, providing certain references for the analyses and calculation of the rice ETc and IQ in similar circumstances.