| Since the 21 st century,China is changing from traditional passive drought management and emergency management to proactive drought management and systematic prevention management in drought risk management.Drought is one of the most common natural disasters in China,which is characterized by long duration,complex formation,frequent occurrence,and wide impact.In the context of global warming,droughts are becoming more frequent and more destructive,posing a more serious threat to China’s agriculture and sustainable socio-economic development.2020,the first national natural disaster risk survey,in which drought disasters are listed as one of the important modules,introduces in detail the objectives,principles,methods,and zoning of drought disaster risk assessment.This represents a new stage in the study of drought risk management in China.This paper selects Xingtai City,Hebei Province as the study area,takes winter wheat as the research object,uses ground meteorological station observation data and MODIS remote sensing data from 1954 to 2019 in Xingtai City,inverts the precipitation condition index,temperature condition index,vegetation condition index and soil moisture condition index related to agricultural drought,constructs a comprehensive agricultural drought monitoring index by entropy weight method,and realizes a comprehensive monitoring index for 2000～2019.The comprehensive agricultural drought monitoring index was constructed by the entropy weight method to achieve dynamic monitoring of agricultural drought conditions during the critical fertility period of winter wheat in Xingtai City from 2000 to 2019,and to understand the spatial and temporal patterns of drought occurrence.Based on the comprehensive monitoring index constructed in this paper,the drought intensity and drought occurrence probability are calculated from the definition of risk,and the comprehensive index method is used to construct a comprehensive zoning index of agricultural drought risk,and the zoning of agricultural drought risk in Xingtai City is realized based on this index with the principle of GN algorithm.Finally,specific drought prevention and control measures are proposed for the risk zones delineated in this paper,in order to provide a scientific basis for future disaster prevention and mitigation,drought disaster management and food security in Xingtai City under the background of climate change.The main conclusions are as follows:(1)Based on the meteorological observation data of Xingtai City,the measured values of precipitation,temperature,and other meteorological elements from 1954 to 2019 were used to analyze the spatial and temporal variation characteristics of meteorological elements in the study area by using one-dimensional linear regression and wavelet analysis,and the results show that: the rain and heat in Xingtai City are the same periods,and the highest values of precipitation and temperature occur in summer;from 1954 to 2019,the precipitation in Xingtai City shows a slow decline from 1954 to 2019,the precipitation in Xingtai City shows a slow decline and the temperature shows a significant increase and the changing pattern of both of them has a certain periodicity.There is a main cycle of a 10 a time scale for precipitation and a main cycle of a 27 a time scale for temperature in Xingtai,which is in a state of low precipitation and high temperature at present and the next few years.Using the precipitation and water demand data from March to May during the critical fertility period of winter wheat in Xingtai City from 2000 to 2019,the water supply and demand situation between the two was analyzed.The results showed that the precipitation in Xingtai City from March to May was far from enough to meet the water required for normal growth and development of winter wheat,and the average water deficit during the critical fertility period of winter wheat was 95 mm.It can be seen that the risk of drought for winter wheat is increasing under the future climate background of less precipitation and higher temperature.(2)Using MODIS remote sensing data,four single drought monitoring indices,namely precipitation condition index,vegetation condition index,soil moisture condition index,and temperature condition index,which are closely related to agricultural drought were inverted,and the Agricultural Drought Monitoring Index(ADMI)was constructed by using the entropy weight method.The index was used to complete the monitoring of agricultural drought dynamics of winter wheat in Xingtai City during the critical fertility period from 2000 to 2019.The results were compared and verified with the disaster statistics and standardized precipitation index of Xingtai City,and the results showed that the index had a better monitoring effect.(3)Based on the precipitation distance level rate,the annual types of precipitation from March to May 2000 to 2019 were divided into three drought year types: type I precipitation partial years,type II precipitation distance level years,and type III precipitation partial years.The monitoring results of agricultural drought under different year types are discussed in groups.The results show that the agricultural drought level is the lowest in type Ⅰ year,mainly light drought,with short drought duration and less distribution area,and the distribution area in the eastern low plain is larger and the frequency of occurrence is higher;the agricultural drought level rises in type Ⅱ year,mainly medium drought,and the drought area is expanded,concentrated in the eastern low plain and central foothill plain;the agricultural drought level is the highest in type Ⅲ year,mainly severe drought and special drought,and the drought duration The duration of drought continues to lengthen,the distribution area expands,and drought occurs in the city.The drought area under different grades in each month was extracted to further explore the time pattern of the occurrence of agricultural drought from March to May,and the results showed that: March was the most prone to drought and had the highest drought grade,April had the lowest drought grade and drought area,and May had the lowest drought grade and the least distributed area,indicating that the drought in Xingtai City was the most severe in March,and with the advancement of crop fertility,the increase of precipitation or timely manual intervention,the drought can be effectively relieved and lifted.(4)Based on the comprehensive agricultural drought monitoring index,the weights were determined according to the degree of impact of the occurrence of drought on winter wheat in different months,and the drought intensity at the like metric scale from 2000 to 2019 was calculated using the comprehensive index method.The agricultural drought intensity coefficients at the township scale were calculated according to the zonal statistics function of GIS,and the frequency of drought occurrence in each township was calculated statistically.From the definition of drought risk,the drought intensity and frequency were reintegrated to construct a comprehensive zoning index of agricultural drought risk,which was imported into GIS and divided into three risk levels using the natural breakpoint method,and the distribution map of the comprehensive zoning index of agricultural drought risk at the township scale was obtained.The results show that 9% of townships in the city are at low risk,39% are at medium risk and 52% are at high risk.From the overall situation,the agricultural drought risk of winter wheat in Xingtai City is characterized by high risk in the central-east and low risk in the west.(5)The agricultural drought risk zoning scheme of Xingtai City was proposed.Taking into account the types of landforms and based on the intensity and frequency of drought,the GN algorithm is used to divide the city into 3 rank zones and 5 risk zones.According to the regional characteristics of each risk zone,measures such as optimizing agricultural production structure,introducing drought-resistant winter wheat varieties,actively promoting and applying new advanced agricultural water conservation technologies such as drip irrigation and sprinkler irrigation,as well as soil improvement and active water transfer are adopted according to local conditions.Applicable disaster mitigation techniques and countermeasures are proposed. |
PDF Full Text Request