Impacts of Land Coverage on Runoff Production and Sediment Yield in the Headwaters of the Yangtze River,China
LI Yuan-shou~1,2, WANG Gen-xu~1,2, SHEN Yong-ping~1, WANG Jun-de~3, WANG Yi-bo~3 (1.Laboratory of Watershed Hydrology and Ecology,CAREERI,CAS,Lanzhou Gansu 730000,China;2.Institute of MountainHazard and Environment,Chinese Academy of Sciences & Ministry of Water Conservancy,Chengdu Sichuan 610041,China;3.College of Resources and Environment,Lanzhou University,Lanzhou Gansu 730000,China)
The small Zuomaoxikongqu River in the headwaters of the Yangtze River,where vegetation is simple and dominated by cold alpine meadows and alpine steppe meadows,are selected as typical catchments to study contrastively the impacts of alpine land coverage change on rainfall-runoff processes and soil erosion.The study indicates that in the field of alpine meadow with 30° slope,the runoff production in the meadow of 30% land-coverage is apparently more than that in the meadows of 92% and 68% land-coverage under the same condition of precipitation.So is sediment yield.The average sediment amount for a precipitation event in the meadow of 30% land-coverage is twice to four times that in the meadows of 92% and 68% land-coverage.Therefore,the erosion amount in the surface in the former is 3~10 times that of the latter two.Under the same precipitation,the runoff production in the meadows of 92% land-coverage is higher than that in the meadows of 68% land-coverage,and the sediment yield is just opposite.The precipitation form has a pronounced effect on the sediment yield.Solid precipitation results in more runoff production and less sediment yield.The study supports the concept of vegetation being a major control factor for runoff production and sediment yield.The simulative results of this study indicate that,for a middle-grade degraded alpine meadow land with coverage less than 68%,it will be apparent runoff production and sediment yield,when the a precipitation event reaches 3.5 mm.Runoff of 2885 mL,2450 mL and 1030 mL have been measured in the field of 25 m2,when precipitation reaches 7.2 mm and lasts 30 minutes.The sediment content in the serious degraded alpine meadow with coverage below 30% is apparently higher,on average,twice to seven times that with high coverage.
【Fund】： 国家自然科学基金项目(30270255);; 中国科学院2004年度“百人计划”项目(Y105065)资助
【CateGory Index】： P334.2
【CateGory Index】： P334.2