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Zhong R.H.,CAS Chengdu Institute of Mountain Hazards and Environment | Zhong R.H.,University of Chinese Academy of Sciences | He X.B.,CAS Chengdu Institute of Mountain Hazards and Environment | Fu K.D.,Yunnan University | Fu K.D.,Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security
Applied Mechanics and Materials | Year: 2013

Changes in stream flow and sediment load in the Buyuan River Basin is a focus due to its vital ecological niche in supply feeding and spawning habitats for upstream migrant fish species of Mekong River. Based on the precipitation and water discharge series data (1959-2008), and sediment load series data (1993-2008), the runoff and sediment discharge variation and its response to precipitation has been analyzed. The results shown that, during the study period of 1959-2008 at the Manan gauging station, annual runoff of Buyuan River has generally decreased, but not significant at the 95% confidence level. However, the decline trend of sediment load was obvious for gauged period from 1993 to 2008. The seasonal runoff distribution in the Buyuan River was uneven and demonstrated an observably "unimodal" distribution. Both water discharge and sediment load are largely derived from wet season (from Jun to Nov), especially in flood season from July to September. During the study period 1993-2008, both annual and monthly observed value of water discharge and sediment load had coincident changing processes. Double mass curves indicated decreasing precipitation was the main reason for runoff reduction in the Buyuan River Basin; declining rainfall and water discharge were two key factors for sediment load reduction. In 2002, however, sediment discharge undergone abrupt change due to huge peak discharge and two consecutive years strong precipitation in the Buyuan River Basin. © (2013) Trans Tech Publications, Switzerland.

Pan H.-L.,CAS Chengdu Institute of Mountain Hazards and Environment | Yang S.,University of Chinese Academy of Sciences | Ou G.-Q.,CAS Chengdu Institute of Mountain Hazards and Environment | Huang J.-C.,Yunnan University | Huang J.-C.,Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security
Journal of Mountain Science | Year: 2013

The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics (density is varying from 1.5 t/m3 to 2.1 t/m3) and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition (particle size and the viscosity of soil). The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non-viscous sand is smaller than the viscous sand. According to the regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation. © 2013 Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.

Fu K.,Yunnan University | Fu K.,Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security | Su B.,Yunnan University | Su B.,Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security | And 7 more authors.
Journal of Geographical Sciences | Year: 2012

The resource development and changes of hydrological regime, sediment and water quality in the Mekong River basin have attracted great attentions. This research aimed to enhance the study on transboundary pollution of heavy metals in this international river. In this study, eight sampling sites were selected to collect the bed sand samples along the mainstream of the Mekong River. In addition, the contents of 5 heavy metal elements and their spatial variability along the mainstream of the river were analyzed. The geoaccumulation index (I geo) and potential ecological risk analysis were employed to assess heavy metal pollution status in the mainstream of the Mekong River. The results show that the average content of the heavy metal elements Zn is 91. 43 mg/kg, Pb is 41. 85 mg/kg, and As is 21. 84 mg/kg in the bed sands of the Upper Mekong River, which are higher than those (Zn 68. 17 mg/kg, Pb 28. 22 mg/kg, As 14. 97 mg/kg) in the Lower Mekong. The average content of Cr in the Lower Mekong is 418. 86 mg/kg, higher than that in the Upper Mekong (42. 19 mg/kg). Luang Prabang has a very high Cr concentration with 762. 93 mg/kg and Pakse with 422. 90 mg/kg. The concentration of Cu in all of the 8 sampling sites is similar, except for in Jiajiu with 11. 70 mg/kg and Jiebei with 7. 00 mg/kg. The results of the geoaccumulation index reveal that contaminations caused by Zn and Pb while Pb and As are more than those by Zn in Upper Mekong. Cr is the primary pollutant in the Lower Mekong, especially at Luang Prabang and Pakse. Slight pollution with As also occurs in Pakse. The potential ecological risk index indicates that the potential ecological risk of heavy metals in the mainstream of the Mekong River is low. We argue that the pollution of water quality and contamination of heavy metals in bed sediment caused by mining of mineral resources or geochemical background values in the Mekong is not transmitted from the Upper to the Lower Mekong because of the reservoir sedimentation and dilution along the river. © 2012 Science Press and Springer-Verlag Berlin Heidelberg.

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