柑橘果园扩张对寻乌水径流和输沙的影响

Impact of Citrus Orchard Expansion on Runoff and Sediment Transport in Xunwu River

土地利用变化的水文效应是当前人类活动环境影响的研究热点。柑橘果园扩张是近20年来寻乌水流域最主要的土地利用变化。利用寻乌水流域3个时期的土地利用数据,设定不同土地利用情景,以SWAT模型模拟不同土地利用情景下的径流与输沙,并结合2000年以来柑橘果园扩张的遥感制图成果和寻乌水径流和泥沙观测资料,分析柑橘果园扩张对流域径流和输沙的影响。研究表明:SWAT模型模拟径流的效果较好(Re=-0.05;R2=0.79;Ens=0.72),输沙模拟效果也在合理范围(Re=0.75;R2=0.8;Ens=0.71);1990~2015年间,寻乌水流域林地面积减少36.83%,果园面积增加42.48%,径流与输沙变化率分别为2.57%和4.27%;新垦果园面积与河道输沙量的关系不显著,这是因为河道输沙不仅与土壤侵蚀有关,同时也与土壤侵蚀地块与河道之间的区位关系有关,同时,在反坡水平阶等水保措施的作用下,果园水土流失得到有效控制。

The expansion of citrus orchard is the most important land use change in the Xunwu River Basin in the past 20 years,which has an impact on the hydrological process in the basin.In this study,land use dataset of three periods were used as scenarios,runoff and sediment was simulated with SWAT model at three different land use scenarios.The annual citrus orchard mapping results were used to analysed the impact from citrus orchard expansion together with sediments loadings in Xunwu River.Results showed:The SWAT worked for runoff(Re=-0.05;R~2=0.79;Ens=0.72)and sediment(Re=0.75;R~2=0.8;Ens=0.71)simulation;The change rate in runoff and sediment from 2005 to 2015 was 2.57%and 4.27%respectively;The the area of forestdecreased by 36.83%and the area of citrus orchard increased by 42.48%during 1990 and 2015;The area of newly reclaimed citrus orchard has a uncertain influence on the sediment content.This is because river sediment transport is not only related to soil erosion,but also to the location of the soil erosion plots.And the soil erosion can be kept down with the vegetation coverage increasing and the water conservation measures such as back-and-slope ground.