| With global climate change,extreme drought events are becoming more frequent in the southern regions of China,causing huge impacts on agricultural production,social economy and ecological environment in the south.The Fuhe River basin is one of the major basins in Jiangxi province,involving numerous large,medium and small irrigation areas,and is an important grain base in Jiangxi Province.However,in recent years,the uneven distribution of water and heat in the basin and the frequent occurrence of drought events have seriously threatened food security production in the region.Therefore,this paper takes the Fuhe River Basin as the study area,and uses the meteorological and hydrological data,digital elevation model(DEM),land use type data and soil type data from 1960 to 2019 to construct a distributed hydrological model of the Fuhe River Basin,simulate the monthly soil water content data in the basin,and use this as the basis to calculate the standardised soil moisture index(SSI)of the Fuhe River Basin to characterise agricultural drought events.Based on the standardized soil moisture index,we analyzed the spatial and temporal characteristics of agricultural drought in the Fuhe River Basin,identified agricultural drought events in the Fuhe River Basin by the theory of runs,and extracted agricultural drought intensity and drought duration characteristics to further reveal the development of agricultural drought in the Fuhe River Basin,using cross wavelet transform theory to discern the correlation between agricultural drought and meteorological factors and to analyse the response of agricultural drought to meteorological factors in terms of time and frequency.Finally,the driving mechanism of agricultural drought in the Fuhe River Basin was assessed using the geodetector model.The main studies and results are as follows:(1)The SWAT model of the Fuhe River Basin was constructed based on the spatial and attribute data of the Fuhe River Basin from 1960 to 2019,and the measured runoff data of Lijiadu,Liaojiawan and Loujiacun hydrological stations in the Fuhe River Basin from 1962 to 2019 were selected to rate and validate the model output data,analysis of sensitivity parameters for the simulation of runoff from the Fuhe River Basin to test the simulation accuracy of the model.The results show that the periodic and validation period R~2 and NSE of Liaojiawan rate are 0.87,0.86 and 0.88,0.87respectively;the periodic and validation period R~2 and NSE of Loujiacun rate are 0.91,0.90 and 0.89,0.86 respectively;the periodic and validation period R~2 and NSE of Lijiadu rate at the total outlet of the basin are 0.91,0.84 and 0.92,0.81 respectively.It shows that the simulation results are highly reliable and the constructed SWAT model of the Fuhe River basin can effectively reflect the real hydrological processes in the basin and can be used as a basic data support platform for agricultural drought analysis in the Fuhe River basin.(2)The agricultural drought events from 1962 to 2019 in the Fuhe River Basin were identified through the theory of runs,and the drought intensity and drought duration characteristics were extracted.The results show that the average drought duration in the Fuhe River basin is 3.97 months,with an average drought intensity of5.29,both drought duration and drought intensity show spatial distribution characteristics of high in the north-south region and low in the central region,and they are highly similar in spatial distribution,with strong drought intensity in sub-basins with long drought duration and weak drought intensity in sub-basins with short drought duration.(3)Wavelet theory(continuous wavelet transform,cross wavelet transform,wavelet coherence analysis)is used to establish relationships between agricultural drought indices and meteorological factors,and to analyse the response of agricultural drought to meteorological factors in time and frequency.Continuous wavelet transform spectrum(CWT)shows that the SSI index correlates well with precipitation,air temperature and solar radiation throughout the study period,while the SSI index correlates well with relative humidity and wind speed for only some of the time.Cross wavelet transform spectrum(XWT)shows that agricultural drought is positively correlated with monthly precipitation and monthly average relative humidity;agricultural drought is negatively correlated with monthly average temperature and monthly average solar radiation;monthly average wind speed affects agricultural drought in different directions in different periods.Wavelet coherence spectrum(WTC)show that precipitation,relative humidity and wind speed only have a large effect on the SSI during some periods,with temperature and solar radiation having a significant effect on the SSI throughout the study period.(4)The geodetector model was used to quantitatively assess the role of meteorological and subsurface factors in driving agricultural drought in the Fuhe River Basin.The results show that the explanatory power of each driver for the SSI index is ranked as follows:temperature(0.401)>solar radiation(0.390)>wind speed(0.344)>altitude(0.200)>relative humidity(0.190)>precipitation(0.150)>slope(0.055)>soil type(0.049)>land use type(0.028).The strong explanatory power of temperature,solar radiation and wind speed for agricultural drought suggests that they are the main drivers of agricultural drought in the Fuhe River Basin,while slope,soil type and land use type have a weaker explanatory power for agricultural drought.The results of the interaction detector show that each driver has a significant two-factor enhanced or non-linearly enhanced interaction on the spatial distribution of agricultural drought,in which the two-factor enhanced interaction of temperature and solar radiation has the greatest effect on agricultural drought in the Fuhe River Basin,followed by the two-factor enhanced interaction of wind speed and solar radiation,and the smallest two-factor enhanced interaction of slope and land use type. |
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