The Spatio-temporal Distribution Of Drought In Hunan Province In Past 36 Years

China's water issues are mainly manifested in threats of floods and drought disasters, shortage of water resources and deterioration of the ecological environment of the 21st century. Among the three problems, the shortage of water resources have become the important restrict factor of the sustainable development of society and economy. Therefore, it is essential to evaluate the degree of the drought of a district and work out the drought preparedness plans. Using 1960-2005a annual precipitation and evaporation, river runoff and drought disaster affected crop areas, the spatio-temporal distribution of regional drought in Hunan Province is analysis by fuzzy comprehension evaluation, linear regression, wavelet analysis, abrupt change analysis,cluster analysisi, EOF and REOF. In addition, the responses between regional drought-flood in Hunan and global change are studied. The results showed that:(1)We have discussed on the causes of the regional drought. Selection of the appropriate evaluation system, established fuzzy comprehensive evaluation model, identified the level of regional drought-flood.(2)The composite indicator in Hunan Province has a weak increasing trend which the 1970s and 1990s were in flood periods, the 1980s were in drought period. There is a decreasing trend entering the 21st century, and there is an abrupt change from dry to wet early 1990s. Generally, the composite indicator presented variations of three periods. In the late 2000's, Hunan Province will be in a period of drought, after then will be in a period of flood.(3)An analysis of evaporation precipitation ratio data found that there are four high-value areas and three low-value areas in Hunan Province. The spatial variations of Hunan Province will be wetness trends except its surrounding areas. The most typical pattern of annual precipitation is the dry-wet consistency. Other typical patterns show the dry-wet difference , for example , wet (or dry) in north and dry(or wet) in south , wet(or dry)in center and dry(or wet) in surrounding areas. The evaporation precipitation ratio distribution exhibits the common features as well as the spatial differences, which can be classified into four types as South Hunan, North, Northeast Hunan and Central Hunan.(4) An analysis of intra-annual dry and wet variations in Hunan Province year by year, it can be divided into six types. Compared with interannual variability of drought and flood, it is prone to drought, normal and flood in normal types.(5) Hunan Province are arid regions except northwest form July to October, and central and north Hunan are in the serious drought region. The most typical pattern of evaporation precipitation ratio is the dry-wet consistency. Other typical patterns show the dry-wet difference , for example , wet (or dry) in north and dry (or wet) in south , wet (or dry) in center and dry (or wet) in surrounding areas, wet(or dry)in northeast and dry(or wet)in southwest. The evaporation precipitation ratio distribution exhibits the common features as well as the spatial differences, which can be classified into four types as South Hunan, Northwest, Southwest and Central Hunan.(6)Regional dry-wet change in Hunan Province was correlated with global climate changes. It is consistent with global drought-flood changes that the 1970s and 1990s were in flood periods, the 1980s were in drought period and a decreasing trend entering the 21st century. Furthermore, the area of drought-flood periodic oscillation with 3 and 6-years is the same as middle reaches of Yangtze River. However it's not fit with drought-flood changes in China in 22a time scale.