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Lai C.,Sun Yat Sen University | Lai C.,South China University of Technology | Chen X.,Sun Yat Sen University | Chen X.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | And 3 more authors.
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2015

According to disaster system theory, 10 indexes are selected with an overall consideration of disaster-inducing factor, the hazard inducing environment and the hazard bearing body. An assessment model of flood risk is constructed based on an intelligent algorithm called Random Forest (RF). Taking a grid of 100 m×100 m as the computing element, the flood risk in Dongjiang River basin is evaluated by the model with the help of GIS technique. The evaluation results show that: the RF model has fewer parameters and dispenses with consideration of index weight and grading standard, making the implementation simpler. It can evaluate the index importance, which maks it convenient to analyze the contribution of each index to flood risk. It achieves higher accuracy, better classification result and stronger data mining ability than the SVM model. It is easy to integrate the GIS technique so that it can conveniently analyze the spatial pattern and inherent law of the risk. Therefore, the assessment model based on RF achieves good results and it can be a new way to flood risk assessment. ©, 2015, China Water Power Press. All right reserved. Source


Chen Z.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | Chen Z.,Sun Yat Sen University | Wei S.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | Wei S.,Sun Yat Sen University
Water Resources Management | Year: 2014

Water security is an important component of regional security and sustainable development and it significantly affects regional development strategies. Flood security, water resource security, and water environment security are the basic elements of a water security system. These elements exhibit dynamic and complex characteristics. System dynamics (SD) is a qualitative and quantitative simulation and analysis method for system integration. SD is applicable to complex system research and has achieved significant results in water security system research. This study initially collected literature on water security research and application in recent years, and then verified the progress and deficiencies in current research. Our research on water security focuses on managing and predicating a single subsystem. Our research on flood control and disaster mitigation focuses on managing and forecasting floods. Our research on water resource security focuses on water resource management, carrying capacity, and planning, as well as on sustainable water utilization. Finally, our research on water environment security includes water quality management, water pollution control, early warning systems, and water ecology. The SD method can properly solve the complicated relations in a water security system but exhibits limitations in the following aspects: research on large systems; influence of social environment changes; uncertainties in water security; and the methods, means, and influence of natural environment changes on water security. © 2013 Springer Science+Business Media Dordrecht. Source


Chen Z.,Sun Yat Sen University | Chen Z.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | Zeng B.,Sun Yat Sen University | Zeng B.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute
International Journal of Sediment Research | Year: 2016

This work investigates the adsorption of Cu ions in sediments by conducting batch experiments, including isothermal experiments and adsorption kinetics experiments. Data from isothermal experiments were analyzed using the Langmuir, Freundlich and Temkin models, and the experimental kinetic data were fit using pseudo-first-order, pseudo-second-order, Elovich, liquid film diffusion and intra-particle diffusion models. The Langmuir model resulted in the best fit for the equilibrium data, which indicated that the adsorption capacity of Cu ions on the sediment was 1.0403mgg-1 with a KL value of 4.2877Lmg-1. The Freundlich and Temkin models also provided good fits, and the nF and A values were 3.8565 and 66.9964L mg-1, respectively, indicating stronger adsorption intensities and adsorption energies between the Cu ions and the sediment. Compared with the pseudo-first-order and Elovich models, the pseudo-second-order model was more appropriate for describing the adsorption kinetics, indicating the chemisorption nature of adsorption. The adsorption kinetic process can be divided into film diffusion, pore diffusion and adsorption reactions. The controlling step for the adsorption kinetics changed with the development of the adsorption process. The entire adsorption process took 180min. Film diffusion was the controlling step for the first 20min. During the 20 to 60min period, the pore diffusion gradually increased and the film diffusion decreased so that both phenomena coexisted. Pore diffusion was the controlling step during the 60-180min period. © 2016 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. Source


Lai C.,Sun Yat Sen University | Lai C.,South China University of Technology | Chen X.,Sun Yat Sen University | Chen X.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Soil erosion is recognized as one of the most serious, global ecological environmental crises in progress today. A rainfall-runoff erosivity factor, combined with the effects of duration, magnitude and intensity of rainfall event, can be used to measure the rain's potential ability to cause erosion. In this paper, the rainfall erosivity model proposed by the Chinese scholar Zhang Wenbo was used to calculate the rainfall erosivity. Taking the Pearl River basin as the study case, daily rainfall data from 1960 to 2012 in 43 meteorological stations were applied in the model. Methods of linear regression, Mann-Kendall, wavelet analysis and Kriging interpolation were applied to analyze the spatial and temporal variations of rainfall erosivity. The results showed that the range of annual rainfall erosivity in the Pearl River basin was 1858.0-14656.6 MJ·mm/(hm2·h) with an average value of 7177.1 MJ·mm/(hm2·h). The average annual rainfall erosivity decreased from east to west in general. Larger values mainly appeared in most areas of Pearl River Delta region, Dongjiang River basin and Beijiang River basin, but the values in Nanpanjiang and Beipanjiang River basin which are the upstream regions of the Pearl River basin were smaller. The distribution of average annual rainfall erosivity was similar with the average annual rainfall and there was a strong correlation (R=0.95, P<0.01) between them. Moreover, the average annual rainfall erosivity generally increased with the increasing of longitude (R=0.712, P<0.01), but decreased with the increasing of latitude (R=0.449, P<0.01). Trends of rainfall erosivity were not significant among years, four seasons, flood and non-flood seasons and no significant mutations occurred in these periods. Among them, the rainfall erosivity showed a slight downward trend in spring and autumn, but a slight upward trend in other periods. Among the periods of upward trend, the rainfall erosivity rising in summer was the fastest with a climbing speed of 11.251 MJ·mm/(hm2·h·a) and the average summer rainfall erosivity reached up to 5 414.530 MJ•mm/(hm2•h). The rainfall erosivity rising in year was the second fastest with a climbing speed of 8.469 MJ•mm/(hm2•h) and the average annual rainfall erosivity reached up to 10235.962 MJ·mm/(hm2·h). In winter, the rainfall erosivity of 39 meteorological stations accounting for about 90.7% of the total stations showed an upward trend, suggesting that the erosivity in winter rose overall. The mutation analysis of rainfall erosivity in the Pearl River basin indicated that the average annual rainfall erosivity sequences of the 7 sub-regions and the whole basin did not have significant mutations. The annual rainfall erosivity of most areas in the Pearl River basin showed significant upward trends (P<0.05), especially at Shaoguan station. In winter, the annual rainfall erosivity at Zhanyi, Fengshan, Hechi, Baise, Liuzhou, Rong'an and Guilin stations also showed significant upward trends. Evidently, the regions represented by these stations faced great pressure in the water and soil conservation. The rainfall erosivity sequence from 1960 to 2012 had the periods of 2.3, 3.8, 6.9, 12.7 and 23.4 a. Among them, only 2.3 and 3.8 a passed the red noise test at confidence level of 95%. The peak value of wavelet variance in 3.8 a was larger than 2.3 a, which suggested that 3.8 a was the main period. The red noise test also indicated that there was an oscillation period of 2.0-7.0 a in the basin. Generally speaking, the rainfall erosivity in the Pearl River basin showed an exacerbated trend, and therefore water and soil conservation should be well prepared. This study has the potential to provide an important reference for soil and water conservation planning, agricultural protection, ecological protection and disaster control in the Pearl River basin. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Chen Z.,Sun Yat Sen University | Chen Z.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | Zhu Z.,Sun Yat Sen University | Zhu Z.,Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong High Education Institute | And 5 more authors.
Water Resources Management | Year: 2014

Studies regarding the temporal-spatial variability of water source quality are crucial for protecting urban drinking water and for urban planning. With 41 typical drinking water sources in Guangdong Province as the research object, this study investigated temporal-spatial trend of different kinds of water sources in different seasons, a subject that has received little attention. The water quality index (WQI) method was used to study the quality of water sources, and the seasonal Kendall testing method was used to analyze the trends in changing water quality. The following results were obtained: (1) Overall, 22 water sources showed tendencies towards improvement and 13 showed a steady trend towards improvement. In addition, 6 sources faced water quality deterioration problems. The quality of the water source and its variations in eastern, northern and western Guangdong are satisfactory. However, the water sources with the poorest quality or that exhibited deteriorative trends were concentrated in the Pearl River Delta. (2) More water sources exhibited improving quality during the non-flood season than during the flood season. In addition, this effect was more pronounced in river-type source water than in reservoir-type source waters. During the flood season, 5 water sources exhibited deteriorative trends. Of these water sources, 3 were river-type. In addition, 18 water sources had improving water quality. Of these, 12 were river-type. During the non-flood season, only 2 river-type water sources exhibited a deteriorative trend. In addition, 19 water sources showed water quality improvements. Of these, 14 were river-type sources. (3) According to the calculated WQI and its temporal variations, this paper suggests that water sources in Guangdong can be classified into four groups, high WQI, saltatory WQI, fluctuant WQI, and low WQI. In addition, the WQI method and seasonal Kendall testing methods are appropriate for investigating the temporal-spatial variability of water source quality and can provide guidance for regional water source planning. © 2014, Springer Science+Business Media Dordrecht. Source

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