Climate change will have a significant effect on crop water requirement (ETc). The spatial and temporal variations of water requirement of maize under climate change are essential elements when conducting a global water security assessment. In this paper, annual reference crop evapotranspiration (ET0) and the crop water requirement of maize were calculated by the single crop coefficient method. The crop water surplus deficit index (CWSDI) and coupling degree of ETc and effective precipitation (Pe) were calculated to analyze the relationship between ETc, ET0, and Pe. The result shows that maize average annual ET0, ETc, and precipitation were 552.97, 383.05, and 264.97 mm, respectively. Moreover, ET0, ETc, and Pe decreased by 3.28, 2.56, and 6.25 mm every decade from 1960 to 2015. The ETc decreased less than Pe did, which led to the decreasing of both CWSDI and the coupling degree of ETc and Pe. The tendency of ET0, ETc decreased first and then increased, while Pe and CWSDI increased first and then decreased, from west to east of the Heilongjiang Province. In addition, the highest ET0, ETc, and lowest CWSDI and Pe were found in the western part of Heilongjiang Province. This study indicated that even though the water deficit in the western region was alleviated and the water deficit in the eastern region grew gradually serious from 1960 to 2015, the drought situation in western Heilongjiang Province should still be taken seriously.
The Water Needs of Grapevines in Central Poland
