The Response Of Crop Water Requirement To Climate Change In The Arid-region Of Northwest China

The crop water requirement（ETc）has closely relationship with regional climate, it is of importancefor planning agricultural water resources, especially for the arid-region in the northwestern of China.According to the statistics, the global temperature has increased by0.6℃since1970s and also in China,and the temperature showed a upward by0.4~0.5℃comparing with the last decades, much higher in thenorthwest. Indicated by investigations on the northwest China, the climate has changed obviously. Theagriculture in the arid region of northwest China has suffered from severe water shortage and imbalancebetween water quantity and land area. Under the background of global warming, it is necessary to evaluatethe spatiotemporal characteristics of ETcas it is sensitive to climate change. Investigation on the ETcin thebackground of climate trend is of necessity and urgent. Observed daily data during1961~2011from152meteorological stations, including temperature, relative humidity, wind speed and sunshine hours, are usedto calculate the reference evapotranspiration (ET0)and ETc, based on Penman-Monteith equation.Mann-Kendall, Pettitt and Inverse Distance Weighted Interpolation are used to analyze the spatiotemporalcharacteristics of the climate and ETc, exploring the ETcresponse to climate change. The results showedthat the annual mean precipitation was246.75mm, the mean temperature in the region is6.09℃while themaximum is13.35℃,the minimum is-0.09℃; the annual relative humidity is52.21, the sunshine hours is7.83h and wind speed is2.63m/s. Precipitation and temperature showed a upward during1961~2011whilethe sunhours, relatively humidity and wind speed got a downward. Apparently, almost all themeteorological variables in the south region of the Loess Plateau were the smallest, while those in asoutheast-northwest strip beside the Loess Plateau were the greatest.The temporal-spatial distribution of ETcon cotton, spring corn, spring wheat and winter wheat in thenorthwest China showed differences during1961~2011. In addition of the winter wheat decreasing, theothers all showed upward trends. The annual mean ETcof cotton was the least503.19mm, spring corn wasthe most,595.39mm, and the mean annual ETcof spring wheat and winter wheat were549.96mm,526.41mm, respectively. The spatial distribution of them was closely to the meteorologicalvariables, whose valueswere the smallest in the south region of the Loess Plateau, while those in a southeast-northwest strip besidethe Loess Plateau were the greatest.Different stations had its significance in temporaldistribution. About30%stations showed significantincreasing of cotton, spring corn and spring wheat,34%significantly decreased at the meantime. Almost14%stations of winter wheat obviously increased while40%decreased. The irrigation water in the arid-regionall increased nearly50year, but the upward rate was low. The agriculture water will still be increasing.