三峡库区腹地忠县小流域近52 a泥沙输移比估算研究

Estimation of Sediment Delivery Ratio in Catchments of Zhongxian County in Central Region of Three Gorges Reservoir from 1963 to 2014

为准确定量估算三峡库区腹地小流域近52 a泥沙输移比,为库区小流域水土保持效益评价提供科学依据,综合采用RUSLE模型、塘库淤积泥沙137Cs和210Pb定年技术分别对黄冲子和工农沟小流域1963—2014年不同时段的泥沙输移比进行了估算。结果表明:黄冲子和工农沟小流域近52 a平均土壤侵蚀量分别为119.72、86.86 t,变异系数分别为0.76、0.86;黄冲子和工农沟小流域塘库淤积泥沙的210PbexCRS模式(Constant rate of supply,CRS)的定年结果与137Cs时标基本一致,不同时段产沙量的变异系数分别为0.28、0.19;黄冲子和工农沟小流域1963—2014年的泥沙输移比均值都为0.25,不同时段泥沙输移比的变异系数分别为0.33、0.82,属于中等程度变异。本研究结果明确了泥沙输移比的估算不能割裂"时段性"这一学术认识,并为泥沙输移比的实际应用提供了借鉴。

Sediment delivery ratio（ SDR） is a critical transfer parameter for investigating soil erosion and sediment yield in a watershed,which is a matter of concern not only because of the sediment yield input to river but also due to its important effects such as safety-operation and flood control in reservoirs.Currently,there is limited information on the quantitatively estimation of SDR for different periods in the catchments of the Three Gorges Reservoir Region（ TGRR）,and its temporal changes of estimates are also scarcely analyzed. Thus,Huangchongzi and Gongnonggou catchments,located in the central part of the TGRR were selected as study areas,which represented one of the typical purple soil areas. In order to investigate the SDR of the past 52 years in the central part of the TGRR strictly according to the definition of SDR,annual average soil erosion was precisely estimated with an integration of geographic information system（ GIS） and the revised universal loss equation（ RUSLE）. Sediment yields for different periods from 1963 to 2014 were identified by pond sedimentation amount based on the dating results of the comprehensive utilization of137 Cs and210 Pb tracer techniques,and these results made use of calculation of SDR for different time-interval. Results showed that the average soil erosion amount was119. 72 t and 86. 86 t and its coefficient of variation（ CV） was 0. 76 and 0. 86 during 1963—2014 in Huangchongzi and Gongnonggou catchments,respectively. The average soil erosion amounts in 2001—2014 were obviously lower than that in 1963—2000 for these two catchments. The main reason was thebenefit of grain to green,which started in 2001. The137 Cs time mark dating-results were in agreement with results by210 Pbexconstant rate of supply（ CRS） model. Based on this analysis,sedimentation core for Huangchongzi and Gongnonggou ponds was segmented with 19 and 12 time-intervals and its CV of the corresponding sediment yields was 0. 28 and 0. 19 from 1963 to 2014,respectively. The SDR fluctuated distinctly from 1963 to 2014,which were especially intensity after human-activities. The CV of the SDR for different time-interval was 0. 33 and 0. 82 from 1963 to 2014 for Huangchongzi and Gongnonggou catchments,respectively. The results estimated strong variations in SDR from 0. 07 to 0. 9 for different time-intervals in the catchments,and this emphasized that the reasonable selection of time-interval played an critical role in estimating SDR,particularly when benefit assessment for soil and water conservation was implemented.