Uncertainty Of Rice Yield Per Unit Area In Qiantang River Basin From 2020 To 2099 Under Climate Change

Global warming and its effects are one of the most important problems in this century.Most studies show that global warming has more negative than positive effects on global rice production.The Qiantang river originates from Anhui province and is the largest river in Zhejiang province.Rice cultivation has a long history in the basin.Rice production remains have been found in the sites of Shangshan mountain and Qiantang lake bridge.Since the reform and opening up,Zhejiang people have achieved fruitful economic results through their own efforts.The rapid development of the economy has accelerated the expansion of urbanization,which has led to the gradual destruction of a large number of cultivated land and intensified the food security of the province.The Qiantang river basin is the main rice-growing area in the province.It is very important to study the effect of future climate change on rice yield per unit area in the Qiantang river basin.The core problems of this paper are divided into two aspects.Firstly,starting from the watershed crop model APEX,taking the Jinhua river basin as an example,the influences of different spatial resolution data combination driving data on the simulation of the APEX model are analyzed,and the influences of different spatial resolution data on the hydrological response unit and crop yield of the watershed are obtained.Then step before the results as the basis to select the appropriate spatial resolution of data driven,using GCMs four global weather patterns and four kinds of typical concentrations of meteorological data from 2020 to 2099 with three kinds of irrigation scenario rice yield is simulated for the Qiantang river basin in the future study,it is concluded that the future changes in the Qiantang river basin,rice yield per unit interval and losses,and has carried on the detailed analysis of the cause of the rice yield loss,and puts forward some countermeasures for adaptation.The main conclusions are as follows:(1)when APEX was used to simulate rice,the yield error per unit area tended to increase as the driving data resolution decreased,compared with the simulation results ofhigh-resolution data sets.Compared with the observed yield results,the yield error per unit area has no obvious trend with the decrease of the driving data resolution.The results show that to save the computation time,the lower resolution can be used to drive the data to simulate the change of rice yield.It should be noted that the results are more applicable to plain crops or paddy crops in hilly areas,and may have different results when simulating other crops in hilly areas.Because of the exponential growth relationship between water erosion intensity and slope,when simulating other crops at different slopes,there will be differences in yield loss caused by water and soil over a long period of time.However,hill terraces have a good effect on soil and water conservation with less soil and water loss,which can be better avoided.(2)under the scenario of global GCMs climate model,the future rice yield reduction trend in the Qiantang river basin is obvious,and the yield loss rate per unit area tends to increase with the increase of emission concentration.Under the scenario of full irrigation,by the 2050 s,the maximum yield reduction rates in Lanjiang river basin,Xin ’an river basin and Fuchun river basin will reach 20.15%,25.45% and 17.51% respectively.By the2090 s,the highest yield reduction rates will reach 40.94% in the Lanjiang river basin,56.16% in the Xin ’an river basin and 32.03% in the Fuchun river basin.In the case of insufficient irrigation,the yield reduction rate will be higher.(3)there are three main causes of yield loss:(1)under the condition of sufficient irrigation,the rise of the lowest daily temperature is the main climatic factor for yield loss;Under the condition of insufficient irrigation,the increase of the daily maximum temperature and the daily minimum temperature is the main climatic factor to decrease the yield.(2)In addition to climatic factors,topographic factors are another important cause of yield loss.Areas with slopes from 5° to 10° are not only threatened by high temperatures,but also risk of water and fertilizer loss,making them the most severely reduced.(3)Rice varieties affect the ability of future rice to withstand high temperature.The optimum temperature for rice growth in Xin ’an river basin is lower than that in the other two basins.