Study On The Response Of Winter Wheat Irrigation Water Requirement To Climate Change In Henan Province

Water resources are the most important resource support and guarantee for agricultural production and are directly related to Chinese food security.Irrigation water requirement is one of the important basis for formulating irrigation quotas,and it is more sensitive to climate change.The global climate is undergoing a significant change characterized by warming.In the past decades,climate change has had an important impact on Chinese total water resources and its spatial and temporal distribution pattern.The uncertainty of agricultural water resources and the contradiction between supply and demand in the context of climate change are further aggravated.Therefore,it is of great significance to study the impact of climate change on irrigation water demand,and to formulate measures and countermeasures for regional agriculture to cope with climate change and safeguard food security in China.Based on the long-term observations at 17 meteorological stations and the projection datasets from general climate models in Henan Province,using statistical analysis methods,the characteristics of the historical long-term spatial-temporal evolution of irrigation water requirement under climate change is studied firstly.Then,the mechanism of irrigation water requirement response to climate change is discussed.Finally,the possible impact of future climate change on winter wheat irrigation water requirement is assessed.The main research contents and results are as follows:(1)The rising trend of temperature(0.3°C/10a)from 1961 to 2015 is found,while the precipitation,relative humidity,wind speed,sunshine duration and so on all showed a decreasing trend.Due to the decrease of crop water requirement(-0.1%/10a)and effective precipitation(-1.6%/10a),the irrigation water requirement was not significantly increased(1.1%/10a),the spatial distribution is mostly characterized with zonal distribution,which generally increases with the elevation of latitude;Compared with the 1961-1990,the irrigation water requirement increased in different degrees in 82.4% stations in 1991-2015,with the average increase of 9.6%,of which the turning green-jointing stage shows the largest increase of 21.8%.(2)Using single factor,sensitivity coefficient and hypothesis scenario,the sensitivity of irrigation water requirement to climate change is analyzed.The sensitivity of crop water requirement to meteorological elements is as follow: relative humidity >solar radiation>temperature>wind speed.The effect of crop water demand on irrigation water demand is more effective.Under the hypothetical scenario of the change of temperature and precipitation,the irrigation water requirement is more sensitive to precipitation than temperature.The decrease of precipitation has greater influence on the irrigation water requirement than the increase of precipitation;With the increase of precipitation,the effect of temperature rising gradually becomes smaller.(3)Based on the temperature and precipitation output data of 25 CMIP5 models under the RCP4.5 scenario,the system bias of the climate mode is corrected by the same ratio scaling method,and the regional climate change scenarios are constructed by using BCC/RCG-WG 3.0 to solve the time series.Compared with the measured values,the relative error of the simulated irrigation water requirement is generally less than 10%,which indicates that the construction of regional climate change scenarios can basically meet the needs of impact assessment.Under the future climate change scenario,the temperature and precipitation during the whole growth period of winter wheat 2021-2050 increased by 1.5°C and 7.7% respectively compared with the baseline period(1961-2000).Among them,in the sowing-overwintering stage temperature increase 1.6°C,in the turning green-jointing stage precipitation increase to 12.3%.(4)During the whole growth period of winter wheat in 2021-2050,the crop water requirement and effective precipitation increased by 4.3% and 6.7%,respectively,and the irrigation water requirement increased by 1.8%.As crop water requirement increased in sowing-overwintering stage(5.8%),the increase of irrigation water requirement was more obvious(16.2%).The more favorable effect of climate change is that the natural precipitation in the heading – maturity stage can basically meet the requirements of water demand for crops(the irrigation water requirement only increased by 0.3%).The irrigation water requirement of 82.4% stations increased in different degrees,however,3 stations in Baofeng,Zhumadian and Gushi in Henan Province decreased less than 3%.The uncertainty of the assessment results showed that although the change trend of irrigation water demand of over 70% sites is the same,the variation of irrigation water demand under different climate models is within 10%.However,there are still large uncertainties in the evaluation results at some stations.