| Affected by multiple factors such as climate,topography,and geology,Heng-Shao-Lou arid corridor is the most serious drought area in Hunan Province.Over the years,scholars have carried out many researches on the drought problem of the Heng-Shao-Lou arid corridor from the perspectives of meteorological and geological conditions,but the existing knowledges cannot fully explain the essence of drought in Heng-Shao-Lou arid corridor.In order to comprehensively deepen the understanding of the causes of drought in Heng-Shao-Lou arid corridor,this paper used the "comparative analysis method"to research the causes of drought in the study area from four aspects,which are meteorological drought,hydrological drought,engineering drought and socioeconomic drought respectively.The main contents and results of the research are as follows:(1)Based on the Standard Precipitation Index(SPI),the runs theory was used to identify the drought characteristic variables of 97 meteorological stations in Hunan Province(from the establishment of the station to 2017).The two-dimensional and three-dimensional joint distributions of three drought characteristic variables,namely,drought duration(D),drought intensity(S)and drought peak(I),were constructed by using Archimedean Copula and Elliptic Copula Functions.Based on this work,the three-dimensional joint distribution established by the optimal Copula Function was used to calculate the joint probability spatial distribution of specific drought events in Hunan Province.And then,the meteorological drought characteristics of the Heng-Shao-Lou arid corridor were presented by comparing the differences of regional scale drought characteristics in Hunan Province.The results of the study show that the probability of drought events in the Heng-Shao-Lou arid corridor is higher than other areas of the province,except for the hilly areas of northeastern Hunan.The most frequent drought events are intra-month and intra-seasonal droughts.And the highest probability of intra-monthly,intra-seasonal and inter-seasonal drought events are generally located in the Loudi area,with a maximum of 0.17.The Hengyang area has a higher frequency of short-duration,high-intensity drought events and long-duration drought events compared to the Loudi area.Overall,the Heng-Shao-Lou arid corridor belongs to the meteorological drought-prone region.(2)In order to study the hydrological drought characteristics of Heng-Shao-Lou area,15 small watersheds,including 6 watersheds of the Heng-Shao-Lou arid corridor,were targed based on the geographical location,geological and topographic conditions and catchment scale,and divided into 7 groups.Based on the Standard Runoff Index(SRI),the runs theory was used to identify the drought characteristic variables of 15 small watersheds,and Archimedean Copula was used to construct the two-dimensional and three-dimensional joint distribution of three drought characteristic variables,drought duration(D),drought intensity(S)and drought peak(I).The three-dimensional joint distribution probabilities of specific drought events in the basin were calculated by using the three-dimensional joint distribution established by the optimal Copula Function.And then,the hydrological drought characteristics and formation mechanism of the Heng-Shao-Lou arid corridor were revealed by comparing the differences of the hydrological drought characteristics and geographical causes in same group of watersheds.The results show that meteorological conditions,watershed topography and geological conditions play a vital role in hydrological drought.The probability of intra-month or intra-seasonal drought events with drought intensity S≤1 and peak I≥-0.75 is relatively high in the basin of the drought corridor.Meanwhile,the distribution of intra-seasonal drought probability is more concentrated,and the intra-month drought event probability varies greatly.The special geographical location,gentle basin topography and hilly terrain made the study area more susceptible to short-duration,low-intensity hydrological drought,while the strong development of karst and the rapid release of water,intensified the short-term hydrological drought,especially intra-monthly.Furthermore,the better karst development further reduces the probability of long-duration drought events in the study area due to the hilly nature,which will increase the probability of high-intensity and longer hydrologic drought to a certain extent.(3)Based on the geological,topographical and other conditions,Hunan Province was divided into nine regions by counties for statistic purposes.More than 14000 reservoirs of various types in the province were investigated to analyze the spatial distribution pattern of reservoirs and the spatial distribution of drought frequency of severe droughts and above from April to September using SPI-3 index method,so as to compare and study the matching relationship among reservoir regulation capacity,drought situation and potential water demand intensity in each geographical division of Hunan Province,and clarify the internal mechanism of Engineering drought in Heng-Shao-Lou arid corridor.The results show that the reservoir distribution in Hunan Province is obviously spatially differentiated.The number density of reservoirs in hilly areas is generally greater than that in mountainous areas,and the reservoir capacity density is generally smaller than that in mountainous areas due to the shortage of large reservoirs.The matching relationships between reservoir water supply capacity and population,reservoir water supply capacity and cultivated land in different regions are also differentiated.Heng-Shao-Lou arid corridor is mainly a small and medium-sized reservoir with poor water supply capacity,and the density of large reservoirs is at a low level in the whole province.The frequency of severe drought is mostly between 6.74%～7.46%.The low regulation capacity of water conservancy projects under the restriction of natural conditions is an important factor affecting the drought situation in the Heng-Shao-Lou arid corridor.(4)Using the calculation methods of Lorenz curve,Gini coefficient and imbalance index,three indicators of population,GDP and cultivated land area were used to study the spatial matching degree of water resources of 14 cities from 2005 to 2020,and the socioeconomic drought degree of the whole province was evaluated based on the water poverty index method to reveal the internal economic and social mechanism of the drought in Heng-Shao-Lou arid corridor.The results show that Heng-Shao-Lou arid corridor is the area with the serious socioeconomic drought in the province.The main drought types in the Heng-Shao-Lou area are moderate drought and severe drought.Hengyang City has the most serious problems of resource-type water shortage and environmental water shortage.Loudi City has serious water shortage and poor utilization capacity of water resources.Shaoyang City’s water resource utilization capacity is even worse,and the resource type water shortage is more serious.The causes of socioeconomic drought in Yongzhou City are relatively balanced,and the intensity of socioeconomic drought is weak. |
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