Study On Water Requirement Law Of Main Crops In Hebei Province

Under the background of global climate change,climate change will change the elements of ecosystem through the comprehensive effect of temperature and precipitation changes,and then affect the law of crop water demand.Crop water requirement and water shortage are the important basis for formulating irrigation water use plan and water resources planning.They have important guiding significance for efficient utilization of water resources,rational arrangement of agricultural irrigation quotas and improvement of grain yield.Hebei Province,as a major agricultural province in China,is the main producer of winter wheat and summer maize.The spatial and temporal distribution of precipitation in Hebei Province is uneven,and water resources are scarce,agricultural irrigation water accounts for more than 70%of the total water consumption,and the situation of water shortage is severe.The annual overdraft of groundwater is as high as 5 billion cubic metres,which forms many underground funnel groups,threatening the safety of water resources,water environment and ecological environment.Therefore,making full use of natural precipitation,exploiting groundwater reasonably and improving the efficiency and benefit of irrigation water have become the main problems faced by agricultural development in Hebei Province.Therefore,this paper studies the law of crop water demand in Hebei Province,in order to provide theoretical data for Hebei Province to cope with the impact of climate change on crop production and improve the efficiency of agricultural water use.Based on the meteorological data and rainfall data of 13 meteorological stations in Hebei Province from 1967 to 2016,winter wheat and summer maize were selected in this paper,based on the crop growth period data provided by the agricultural sector and with the help of a series of crop water demand calculation methods recommended by the Food Organization of the United Nations?FAO?,using inverse distance weighted interpolation method?IDW?,Mann-Kendall method and wavelet analysis method discussed the temporal and spatial distribution of reference crop evapotranspiration?ET₀?,water requirement?ET_c?and water shortage?W?of winter wheat and summer maize in Hebei Province;At the same time,in order to study the relationship between climate factors and ET₀,the temporal and spatial analysis of climate factors in Hebei Province was carried out,and the correlation coefficient and sensitivity coefficient between ET₀ and climate factors were calculated by correlation analysis and sensitivity analysis;In order to explore the impacts of climate change on water demand,the spatial variations of crop water demand and water shortage in three typical years?2030,2050 and 2070?in the future based on the baseline period?2007-2016?were explored using the scenario data of future A₂ and B₂ climate change.The main conclusions are as follows:?1?During the study period,annual ET₀ showed a downward trend,and the order of four seasons was summer>autumn>spring>winter.Water demand and water shortage of winter wheat and summer maize showed a downward trend,and there were 33 years of main cycle and 19 years of secondary cycle.The mutation year of summer maize water shortage is 2004.ET₀ decreases from east to west in the south-central part of Hebei Province and from southeast to northwest in the northeast part of Hebei Province;During the whole growth period,the water demand of Winter Wheat in the south-central part of Hebei Province decreases gradually from northeast to southwest,while that in the northeast part decreases gradually from southwest to northeast;The water shortage of Winter Wheat in the south-central part of Hebei Province decreased gradually from Nangong to the East and West sides,while that of northeast part decreased gradually from coastal to inland;The water demand and water shortage of summer maize decreased gradually from northeast to southwest.The water demand and water shortage of winter wheat and summer maize reached the maximum during the rapid development period,and the spatial distribution law was different.?2?During the study period,the annual average temperature,maximum temperature and minimum temperature of Hebei Province showed a significant upward trend,while precipitation,wind speed and sunshine hours showed a significant downward trend,while relative humidity showed a non-significant downward trend,among the climatic factors,only the mean temperature has a sudden change,which occurred in 1988.The mean temperature,maximum temperature and minimum temperature in the central and southern part of Hebei Province are gradually decreasing from south to north;The spatial distribution of precipitation is low in the middle and high around,with the lowest in Nangong;Relative humidity and wind speed decreased gradually from east to west,while sunshine hours decreased gradually from northeast to southwest;The distribution characteristics of temperature in northeastern Hebei Province are higher in Southeast than in northwest.The precipitation and sunshine hours increase gradually from south to north,and the relative humidity and wind speed decrease gradually from southeast to northwest.In each region,the temperature tends to increase,the wind and sunshine duration showed a decreasing trend,the precipitation and relative humidity are increased and decreased two trends.?3?Qualitative analysis results show that:the first four main factors affecting annual ET₀are sunshine hours,wind speed,relative humidity and maximum temperature.The dominant factors affecting ET₀ in the four seasons are constantly changing.Quantitative analysis results show that:the absolute values of the sensitivity coefficients of the annual average ET₀ are ranked as follows:S-RH>S-Tmax>S-U>S-N>S-T>S-Tmin,that is to say,the first four main factors affecting ET₀ in the study area are relative humidity,maximum temperature,wind speed and sunshine hours.which were consistent with the results of correlation.The order of absolute values of sensitivity coefficients of four seasons ET₀ is different;The contribution of climate factors to ET₀ shows that:the decrease of ET₀ in spring,autumn and winter is mainly affected by the decrease of wind speed,and the decrease of ET₀ in summer is mainly affected by the decrease of sunshine hours.?4?Under A₂ and B₂ scenarios,compared with the base period,the water demand of winter wheat will increase in the next three typical years,and with the increase of years,the more the increase,the increasing trend of water demand of summer maize was smaller than that of winter wheat;In both situations,the water shortage of winter wheat decreased in Zunhua,increased in other areas,water shortage of summer maize showed an increasing trend.Compared with A₂ scenario,the growth rate of water demand and water shortage of winter wheat and summer maize in B₂ scenario was smaller,and the spatial difference was not obvious.