Research On The Precipitation Change And Its Impacts In Hexi Area

Water resource is the lifeblood of productions and life in Hexi area, whereas the precipitation is the main supply of the water resource, therefore, study the rules and characteristics of precipitation change is important to know the characteristics of the water resources and to instruct the ecology construction and restoration.In this paper, by using the latest version of higher solution grid data set, named as CRU-TS2.1, which released by the University of East Anglia a precipitation series of recent 60 years in the Hexi area is established and analyzed fristly , based on it, a precipitation series of recent 102 years in Qilian mountainous area is established by using treering in Qilian mountainous area and the Drought and Flood Grades as well as the historical document, and the change trendency, the periodicity and the abrupt change of the precipitation are analyzed, at last, in view of the big droughts which happened in 20th in Hexi ,we discussed the impacts of the precipitation change to the development of the economic and the society.The main results show as following:(1) It is arid and semi-arid climate in Hexi area , the precipitation is scarce and distributed unevenly, and it is abundant in the Qilian mountainous area and scarced in Hexi corridor.(2) During resent 46 years there exist slight increase trend of the precipitation in the whole area.(3) Influenced by different terrain, geographical position and climate system, there are a slight difference in the characteristics of precipitation change in each part of Hexi area: The Qilian mountain area has the most abundant precipitation, the average multi-annual precipitation is 345mm, and the east area is next, the average multi-annual precipitation is 220mm, the west part with a annual precipitiaon of 84mm and the Mazongshan mountain area is the most rainless area with a 74mm. In recent 46 years, the precipitationin in the east part has lesser increase while the precipitation in the mountain area increase slightly, and there is no significant changes in the West part, whereas the precipitation in the Mazongshan mountain area reduced slightly.(4) From 1901 to 2002 year, the precipitation in the Qilian mountain area has increased slightly, and, in the earlier of 20th, the scope of the precipitation change is small ,however ,it is get bigger later . There are three substained period of deficient precipitation in the 20th in the area, respectively, from the middle of the 20s to the middle of the 30s and from the end of 50s to the middle of 60s as well as at the end of 20th to 2001.(5)Through spectrum analysis and the wavelet analysis, there is a 4-year and a 5-year periodic oscillation in the change of the precipitation in the area, and 2-year is anther significant period , however , there also have 7-year , 12 to 17-year and 32 to 37-year periods in the area. As a approximatel separatrix, before 1980 the main period was small, mainly 3 to 5-year and after 1980 it is about 7-year, so it is obviously that the period of the precipitation is trun upward and the precipitation oscillation is change from frequently to stably.(6) The jumps have been examined in terms of 5-year moving averaged annual series by using moving t-test(MTT)method and Yamamoto method, The results showed that four abrupt changes took place in the 20th in the Qilian mountain area ,In 1925 and 1954 the precipitation has experienced a abrupt changes of abundant to short, and in 1940 and 1964 from short to abundant .the abrupt change in 1987 to 1989, which is recognized by the other studies, has not significant in a century time series, that is a important discovery.(7) The precipitation changes in Qilian mountain area have affected to the water resources, droughts and famines as well as the development of the economic and society. The three big droughts(the big drought took place in 1929, the drought happened in 1962 and the drought happend at the end of 90s)which took place in the 20th were corresponded to the three substained period of deficient precipitation in Qilian mountain area .And the drought also shows a 33-37 year periodic oscillation, with uniform to the period of the precipitation.(8) Carrying on artificial rain and snow enhancement in Qilian Mountain area, enhancing management, distribute and use water reasonably, and advancing the capability to disaster and droughts are the useful approaches to strengthening the adapt ability of society to climate change and realizing sustainable development.