On Drought-Flood Disasters In Wei River Basin

Wei River basin is the birthplace of Chinese civilization, which involved inGansu, Ningxia, and Shaanxi provinces (districts). Wei River basin is located at theSouth edge of the loess plateau, northern slope of Qinling Mountains, a continentalmonsoon climate, arid and humid areas of the transition zone. Natural ecosystemsvulnerable, sensitive to climate change, natural variability against poor. Droughts area major meteorological disaster in Wei River basin, and seriously affect the economy,especially in agriculture. By recent540years of drought and flood level information,and nearly50years measured rainfall data, We analysis drought trend andtemporal-spatial distribution characteristics and study on relationship between droughtand flood disasters and climate change and the drought events.1. Drought-flood evolution in Wei River for recent540yearsDrought climate mainly appeared in the end of15th century,16th century, andhumid climate occupy the superiority in the18th,19th century;17th,20th centurybelongs to a normal century.In Wei River basin climate change in the recent540years, there are11th floodand drought stages, that is:1470-1533relative flood stage;1534-1580drought stage;1581-1641relative flood stage;1642-1708drought stage;1709-1720droughtstage;1721-1783relative flood stage;1784-1811drought stage;1812-1914relativeflood stage;1915-1928drought stage;1929-1966relative flood stage;1967-2010drought stage.By wavelet analysis method, we find the drought-flood level has periodicalfeature371a,223a,151a,114a,72a.By sliding t tests, there were seven abrupt points in Wei River basin droughtyears, and all occurred in the1481,1492and1534,1579and1593,1628and1642,1683,1828, and there is a century-scale abrupt change year of1642.In the droughtsand floods climate evolution of Wei River basin during the recent540years, big drought year appeared84times, big flood year appeared74times, Big droughts yearshave the slightly larger number of emerging opportunities than big flood years.2. Analysis on the spatiotemporal change of flood and drought in recent50yearsWei River basin near50years in the dry flood and drought appears of frequencybasic same; the changes trend of flood and drought in recent50years does notsignificantly.Wei River basin near50years has periodical feature34a,15a; and has a abruptpoints in1966.There are6th flood and drought stages, that is:1960-1966relative flood stage;1967-1979drought stage;1980-1984relative flood stage;1989-2003drought stage;2004-2010relative drought stage.The drought year at least appears had6times all meteorological stations; exceptLuochuan, Wuqi,Huanxian, and Pingliang, and Xiji site outside are occurs continuousdrought event in1994-1995; Xian and Wugong station occurred three years continueddrought in1993-1995, Tianshui Station occurred drought event in1994-1997,Pingliang occurred drought event in2007-2009; which Armand1983-1984, Huashan,Xian,Wugong, Baoji occurred flood events in1983-1984, these sites are basic inmiddle and lower reaches of Wei River; also2009-2010Huashan, Xian occurredflood events; Xiji occurred flood events in1967-1968.3. Study on the relationship between climate change and drought and flood anddrought and flood disasters eventsWei River basin flood and drought and climate change good overallcorrespondence in recent540years, shows climate change is a leading cause ofdrought and flood.There were serious drought disasters events in1581-1588s,1632-1640s,1875-1878s in Wei River basin; and1662s,1755-1757s,1904s had flood disasterevents, these events in history have caused a tragic scene, such as death, famine,migration of population, social unrest and even regime change.