| To explore grape water surplus and deficit in the semi humid area of western Guanzhong, inter-annual change feature of grapes during 1990-2019 was analyzed using Mann-Kendall trend test, sliding t-test and Morlet wavelet analysis.Based on the crop water surplus deficit index (CWSDI), the water supplies in each month and the whole growth period were analyzed to offer referential guidance for grape irrigation scientifically in Guanzhong. According to the results, during the whole growth period, the major water demands of grapes unexpectedly changed in 2015 and then increased. The first main cycle of water demands change was 15 years. The water demands of grape underwent first increase and then decrease during the whole growth stage. The difference of water requirement of each hydrological year reached the maximum amount during the fruit expansion period. Drought was likely to happen in different hydrological years, in which, June was exactly the season for the expansion of grape fruits. However, CWSDI took on a decrease trend. Therefore, considering the reality,water contents of grapes should be monitored to prevent harvest failure from water deficit. |