Drought Risk Assessment Of Maize And Wheat Cropping In Ningxia,China

Ningxia Autonomous Region is located in the northwestern part of China,where rainfall is scarce and uneven spatially and temporally.Drought has become the most serious natural disaster affecting Ningxia's agricultural production,which has caused huge property losses to farmers and hindered the development of agricultural economy in Ningxia.With the intensification of climate change and increasing of human activities intensity,the drought situation in Ningxia is not optimistic.Comprehensive assessment of drought risk is conducive to grasping the differences in spatio-temporal distribution of Ningxia drought risk,clarifying the direction of efforts for drought prevention,and further strengthening agricultural drought risk management.This study is to analyze and assess the temporal and spatial pattern of drought risk in maize and wheat cropping in Ningxia of China using a comprehensive method that emphasizes the factors leading to happening of drought.Drought risk assessment of maize and wheat cropping in Ningxia was done from four aspects: the possibility of drought happening during the growth period of maize and wheat cropping,the vulnerability of maize and wheat cropping under drought attack,the sensitivity of maize and wheat cropping to drought environment,and the capability of reducing drought's attack in each county.A comprehensive model was constructed from these four aspect to compute a drought risk index for the assessment in Ningxia.A number of relevant parameters indicating the above four aspects of drought risk have been choose for the assessment.The following data had been used for the study.Meteorological data from various observation stations in Ningxia for the 1981-2016 years,information about maize and wheat growing period,statistical data on yield and acreage of maize and wheat cropping during the 1993-2016 years,basic geographical information on Ningxia,and the historical data of drought disaster occurred in Ningxia.Drought index for each of the above four aspects was computed and then a comprehensive index was calculated from these four indices to indicate the drought risk of maize and wheat cropping in Ningxia,which was used to analysis the temporal and spatial change of the drought risk during in Ningxia.The results show that:(1)Spatial distribution of hazard of maize and wheat cropping in Ningxia was featured with high in the middle region and low in the north and south parts.Both maize and wheat drought risk areas were distributed in Tongxin and Zhongwei counties and the risk index was above 0.5 and 0.55 respectively.Maize has higher drought hazard possibility than the wheat in the north of Ningxia,while lower in the middle and south of Ningxia.Under the hypothesis of the same irrigation conditions(North Yellow River irrigation area),maize has a longer growth period and higher potential evaporation capacity than wheat,so the drought risk is relatively high.While for the rain-fed agricultural region(counties in middle and southern Ningxia),crop water mainly depends on natural precipitation,maize growth period is in accordance with the rainy season and during the wheat birth period precipitation is less,thus wheat drought risk is higher.(2)The spatial distribution area of low sensitivity for maize and wheat drought in Ningxia is mainly continuously distributed in the fluvial plain around the Yellow River;the topography is flat,mostly silt-filled and tidal soil,which is favorable to crop growth.While the distribution area of high sensitivity for maize and wheat drought is mainly in the Helan mountainous region and in the middle area of Ningxia.The soil types in this area are mostly calcareous and sandy,and high exposure of maize and wheat.Considering the influence of slope,soil type and exposure of maize and wheat,the drought sensitivity of maize and wheat mainly depends on its exposure index.(3)The low drought vulnerability areas of maize and wheat in Ningxia are concentrated in the water areas along the Yellow River.The irrigation conditions in this area are good and suitable for the development of modern agriculture.The high drought vulnerability areas of maize and wheat include Haiyuan,Tongxin,Guyuan,Xiji,Wuyuan,Longde,Pengyang,and other counties are in middle and southern of Ningxia,where the yield reduction of maize and wheat is high,and the coefficient of variation of yield is large.The vulnerability is highest under drought threats.(4)The regions with strong agricultural drought resistance in the counties of Ningxia are mainly located in the surrounding counties and cities of the Yellow River irrigation area.The drought resistance index is above 0.5.In this region the level of agricultural economic development and farmers' income level is relatively high and the mechanization level is relatively good.Therefore,the drought resistance is high.The regions with low drought-resistance capacity are Zhongwei,Central Xiji and northwest Pingluo,and the drought resistance index is between 0.4 and 0.45.The time series distribution of drought-resistance index in all counties(cities)of Ningxia showed a significant upward trend.By 2016 the average drought-resistance index of each county reached 0.8.(5)The drought risk of maize and wheat in Ningxia from 1990 to 2016 ranged from 30% to 45%.Among them,the drought risk of maize was higher which shows a gradual upward trend,and the drought risk trend of wheat was relatively flat.The spatial distribution of drought risk in maize and wheat is relatively consistent.The low drought risk areas are mainly distributed in the counties(cities)in the northern part of the Yellow River irrigation area which have 20% drought risk.These areas have rapid economic development,good irrigation conditions,and fertile soil.The regions with higher drought risk are mainly concentrated in the middle and southern regions those have more than 50% drought risk.The soil in those regions has poor water holding capacity,loose soil structure,backward economic development,and old agricultural equipment,which seriously affects crop yields.Among the four indicators of crop drought risk assessment,the risk index has the highest weight,and the spatial distribution of drought risk and drought risk are more consistent.The drought risk of maize and wheat in Ningxia region largely determines the distribution of drought risk.In the study,we used available relevant data of different aspects and constructed the drought risk assessment model of maize and wheat cropping in Ningxia based on comprehensive evaluation method.Analysis of space-time distribution of the drought risk is given,which can provide a scientific knowledge for the agriculture production,planning of drought prevention and drought risk management in Ningxia in future.