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Alternative TitleSediment Delivery Ratio of a small watershed in the Three Gorges Reservoir Region based on GIS and Cesium-137 Tracing Techniques
Thesis Advisor文安邦
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name硕士
Degree Discipline土壤学
KeywordGis技术 137cs示踪技术 三峡库区 小流域 泥沙输移比
Abstract 三峡库区是我国水土流失最为严重的地区之一,小流域侵蚀产沙以及泥沙输移比是一个备受关注的问题。由于径流小区观测资料少和水文站空间布局的限制,三峡库区小流域侵蚀产沙以及泥沙输移研究基础薄弱。GIS技术结合137Cs示踪法的研究方法和研究思路,为定量研究小流域泥沙输移比提供了很好的途径。    论文选择位于重庆市忠县石宝镇的菱角塘小流域(0.105km2)为研究对象,基于137Cs示踪技术,借助GIS技术对菱角塘小流域进行侵蚀单元的划分,并通过137Cs示踪技术配合GIS空间插值法,结合实地调查,对流域内坡耕地、林地、水田、塘库等土地利用类型侵蚀产沙空间分布格局展开研究,并评估小流域1963年以来的坡面侵蚀量;同时,以137Cs定年法为主要研究手段,确定塘库不同层位的淤积泥沙的年龄,评估1963年以来小流域塘库泥沙淤积量,分别获得小流域以塘库入口和出口为观测断面的泥沙输移比。论文主要研究结论如下:    (1)从1963-2013年这50年间,小流域平均侵蚀模数为1379.1 t/(km2.a),侵蚀总量为7240.5 t,其中,林地平均侵蚀模数901 t/(km2.a),侵蚀总量为2095.0 t,占小流域侵蚀总量的28.9%,坡耕地平均侵蚀模数2360.3 t/(km2.a),侵蚀总量为5145.5 t,占小流域侵蚀总量的71.1%。坡耕地侵蚀总量是林地侵蚀总量的2.45倍。林地(N)面积接近于林地(S)面积的两倍,从计算结果来看,林地(N)侵蚀强度大于林地(S)。林地(N)的平均侵蚀强度1160 t/(km2.a),土壤侵蚀量为1450.0 t,林地(S)平均侵蚀强度600 t/(km2.a),土壤侵蚀量为645.0 t。    (2)利用137Cs断代技术,确定1963年137Cs蓄积峰位于60cm处的沉积层位,运用沉积物堆积速率法和锥台法两种方法计算得到的塘库淤积泥沙量分别为1930.7t和1927.5 t,两者结果基本一致。    (3)利用泥沙平衡理论,计算得出小流域水田泥沙淤积量4670.0t,占小流域侵蚀总量的64.5%;塘库泥沙淤积量为1927.5t,占小流域侵蚀总量的26.7%;输出小流域的泥沙量643.0t。占小流域侵蚀总量的8.8%。    (4)菱角塘小流域以塘库入口作为观测断面的泥沙输移比为0.36,而以塘库出口作为观测断面的泥沙输移比为0.088。说明修建塘库可以有效拦截流域坡面产沙,从而减少汇入主河的泥沙量。
Other AbstractThree Gorges Reservoir Region (TGRR) was one of the severest soil erosion regions in China. Therefore, erosion and yield in the small watershed as well as its sediment delivery ratio (SDR) was to paid more attention by researchers than other problems. Currently, the combination of GIS and 137Cs tracer technique provides a new method for quantifying the SDR of the small watershed because of the limitations of traditional methods such as runoff plot and hydrological station.     The Lingjiao pond small watershed with the area of 0.105 km2 located in the Shibao town of Zhongxian County, Chongqing municipality city was investigated in this paper. The erosion and deposition elements in the Lingjiao pond small watershed were classified by GIS and 137Cs tracer techniques which were also utilized for interpolating based on the measured 137Cs data and filed investigation. In the following, the spatial distribution pattern of erosion and sediment yield for different land use types (sloping cultivated land, forestland, paddy field and pond) was carried out and then assessed the slope erosion amount since 1963 year in the small watershed. In addition, the 137Cs-dated method was applied for quantifying the age of different layer of the sediment siltation in the pond. It was apparently that the sediment siltation amount in the pond was easily calculated and finally the SDR under different conditions (entrance or exit of the pond) was observed. The critical conclusions in this paper were following :    Soil erosion under different land use types varied greatly. The erosion modulus was 1379.1 t/(km2.a) and total erosion amount was 7240.5 t in the lingjiao pond small watershed, which total erosion amounts of forestland and sloping cultivated land were 2095 and 5145.5t, respectively with the ratios of total erosion amount in the small watershed were 28.9% and 71.1%, respectively. The erosion modulus of forestland and sloping cultivated land were 901 t/(km2.a) and 2360.3 t/(km2.a), respectively. It was obviously that the erosion amount of sloping cultivated land was 2.45 times more than that of forestland. With respect to the forestland, erosion amounts in the northern forestland and southern forestland were 1450t and 645t, erosion modulus were 1160 and 600 t/(km2.a), respectively. This can be explained by the fact the resident zones randomly distributed nearby the northern forestland played a negative role in soil conservation and therefore made great intensity of soil erosion in the northern forestland whereas the southern forestland did not.    The maximum peak value of 137Cs in the sediment profile was observed and its depth layer was about 60cm with the utilization of 137Cs-dated technique. The pond sediment siltation amount was calculated by deposit sediment accumulated rate -and cone- method, which its results were 1930.7t and 1927.5t, respectively. The result estimated by deposit sediment accumulated rate method was in agreement with that estimated by cone method to large extent, which indicated both methods had valuable scientific to some degree.    According to the principle of sediment balance in the small watershed, the slope total erosion amount, paddy filed siltation amount, the pond sediment siltation amount and the output sediment amount was 7240.5t, 4670t, 1927.5t and 643t, respectively. It was clearly that sediment siltation ration of paddy filed and pond occupying the slope total erosion amount was 64.5% and 26.7 %, respectively although only 8.8% of the slope erosion amount was transported out of the pond. On the basis of the former observation, the sediment siltation amount from in-out pond was 2570.5t and the sediment yield in the Lingjiao pond small watershed was 2570.5t.    The SDR was 0.36 when the entrance of pond was regarded as observation
Document Type学位论文
Recommended Citation
GB/T 7714
张一澜. 基于GIS和137Cs技术的三峡库区小流域泥沙输移比研究[D]. 北京. 中国科学院研究生院,2014.
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