| Land use/cover change is the key research field in global change research,Land use changed would influenced hydrological process and lead to runoff changed finally,so it is the key filed for hydrology researchers.This article chose the Yangtze River Basin as research object,analysed recent 35 years land use change features of temporal and spatial.Then built watershed hydrological model,quantitatively calculated change runoff,to evaluated the basin's land use change effect on runoff,research results shows:(1)Recent 35 years the Yangtze River Basin land use change features as follow: Among 1980~1990 and 2000~2005,land use change speed much faster than 1990~1995 and 1995~2000,in the first period(1980~1990)and 4th(2000~2005)average swapping variable values were 0.61 and 0.45 respectively,much bigger than middle two periods(1990~1995 and 1995~2000),which were 0.09 and 0.08 respectively.Upper reaches of the basin in the middle of Sichuan,the swapping variable values are relatively larger in spatial distribution,it was the most active zone in land use interchangeable,secondly was in headwater zone,and the middle and lower reaches was the least active zone.There were different features in different kinds of land use,cultivated lands,water body,construction land and unused land's area increased in first two periods and decreased in last two periods,woodland and grassland changed on the contrary.Middle and upper reaches was most influenced by human active and natural disasters so it was changed obviously,human destroyed woodland and overgrazing made woodland and grassland decreased greatly and changed into unused land in upper reach.Woodland and cultivated lands interconversion in middle and down reaches,in down reaches a lot of water body changed into unused land and paddy field in early stage,while later period increased water body most came from unused land and paddy filed.Construction land was the most obvious increased land use,especially in developed downstream area.(2)The model calculated results show that land use changed had an obviously influenced in runoff,under different kinds of land use condition,daily average annual runoff,average flood period and drought period runoff all changed.11 hydrological stations changed as follow: in Zhimenda Station,Pingshan Station and Xiaodeshi Station in Yajiang River,and Poyang Lake river systems all decreased,Pingshan Station decreased 8406.23 Million m3,with a decrease range of 5.03%,it decreased the most among all the stations.Remaining stations,Gaochang Station,Beibei Station,Wulong station,Huangzhuang station,Chenglingji station and trunk stream station of Yichang and Datong's runoff all increased.Annually run off in Beibei Station of Jialingjiang have a biggest increase range,annually run off increased 5200.6 Million m3 with a range of 9.32%,while Gaochang station of Mintuojiang River increased relative small,only37.84 Million m3 with increased range of 0.05%,and the station of Datong,located in down trunk stream,increased annually runoff by 782.09 Million m3 with a range of 0.08%.Most stations flood period and drought period runoff change consistent with annually runoff,increased or decreased at the same time,but not in Yichang station,Chengliji and Datong station.The result show that 10% flood in stations above Pingshan Station,Yichang and Hukou Station all decreased,Pingshan decreased most with a rate of 2.67%;flood in Beibei,Huangzhuang et,al.increased,the biggest increased rate was 3.48%.Low flow in Beibei,Yichang et,al.increased,most stations low flow decreased,which in Hukou decreased most with a decreased rate 68.70%,land use change had a bigger influence on low flow.after land use change in the Yangtze River Basin,runoff in Pingshan station above and Poyang Lake river systems all decreased,and middle and down reach's runoff will increased. |
PDF Full Text Request