Abstract: Based on the last 50 years meteorological data from 10 stations (including five stations for winter wheat and five for spring wheat) in Hedong region of Gansu Province, and by using FAO-recommended Penman-Monteith model, the water requirement and water deficiency of winter wheat and spring wheat in the study region were calculated. Meanwhile, by using MannKendall method to analyze the variation trends of the water requirement and water deficiency, the major meteorological factors affecting the variations of wheat water requirement were obtained by correlation analysis. The future trends of the wheat water requirement were forecasted by the method of rescaled range analysis. In the study region, the water requirement of winter wheat in Huanxian had a slight decrease, while that in Kongdong, Tianshui, Wudou, and Xifeng presented an increasing trend. The water requirement of spring wheat in Jingtai decreased, while that in Lintao, Linxia, Minxian, and Yuzhong exhibited an increasing trend. The water deficiency of winter wheat in the study region all showed an increasing trend, with a rate of 7.32-25.19 mm·10 a^-1. The water deficiency of spring wheat in Jingtai showed a decreasing trend, with a rate of 20.81 mm·10 a^-1, while that in Lintao, Linxia, Minxian, and Yuzhong showed an increasing trend, with a rate 0.42-20.4 mm·10 a^-1. The major meteorological factors affecting the water requirement of winter wheat were the mean daily air temperature and wind speed, while those
affecting the water requirement of spring wheat were the mean daily temperature, relative humidity, and wind speed.

Key words: wetland, optimization, petroleum pollutants, simulation., purification ability