ALBERT

Description: The abrupt changes in the streamflow and sediment load at nine hydrological stations of the Pearl River basin were systematically analysed by using the simple two-phase linear regression scheme and the coherency analysis technique. Possible underlying causes were also discussed. Our study results indicated that abrupt changes in the streamflow occurred mainly in the early 1990s. The change points were followed by significant decreasing streamflow. Multiscale abrupt behaviour of the sediment load classified the hydrological stations into two groups: (1) Xiaolongtan, Nanning and Liuzhou; and (2) Qianjiang, Dahuangjiangkou, Wuzhou, Gaoyao, Shijiao and Boluo. The grouped categories implied obvious influences of water reservoirs on the hydrological processes of the Pearl River. On the basis of analysis of the locations and the construction time of the water reservoirs, and also the time when the change points occurred, we figured out different ways the water reservoirs impacted the hydrological processes within the Pearl River basin. As for the hydrological variation along the mainstream of the Pearl River, the water reservoirs have considerable influences on both the streamflow and sediment load variations; however, more influences seemed to be exerted on the sediment load transport. In the North River, the hydrological processes seemed to be influenced mainly by climate changes. In the East River, the hydrological variations tended to be impacted by the water reservoirs. The study results also indicated no fixed modes when we address the influences of water reservoirs on hydrological processes. Drainage area and regulation behaviour of the water reservoirs should be taken into account. The results of this study will be of considerable importance for the effective water resources management of the Pearl River basin under the changing environment. © 2011 John Wiley & Sons, Ltd.

Description: Probability behaviours and trends of hydrological extremes, the 7-day high flow (HF7) in this study, of the Poyang Lake basin are thoroughly investigated using 11 probability distribution functions and Mann-Kendall trend test method. Parameters and goodness-of-fit of the probability functions are estimated using the L-moment technique and Kolmogorov-Smirnov statistic D (K-S D). The hydrological data are extracted from six major hydrological stations located in the five main tributaries of the Poyang Lake basin. The results indicate that: (1) the Wakeby distribution is the good choice for description of the statistical behaviours of HF7 in the study region; (2) changing properties of HF7 are varying from on station to another, implying different fluvial geomorphological features, climate changes, and human activities within different tributaries. Generally, the HF7 events are increasing after the construction of water reservoirs except the Wan'an water reservoir. The analysis results demonstrate considerable influences of water reservoirs on high flow changes. Relatively low design standards of the water reservoirs greatly limit the functions of the water reservoirs in terms of flood control. Besides, most water reservoirs were built in the tributaries of the Poyang Lake basin, exerting limited influences on the streamflow extremes; (3) higher frequency of hydrological extremes may cause higher probability of floods, posing increasingly serious challenges for flood control. In this sense, more efforts should be paid to enhance human mitigation to natural hazards such as floods in the Poyang Lake basin. © 2011 John Wiley & Sons, Ltd.

Description: Extreme events are drawing increasing concerns in recent decades due to their catastrophic nature. In this case, we thoroughly analysed the statistical behaviours of hydrological extremes in the south China by taking Guangdong province as a case study because of its unshakable position in the economic development in China. Our results further corroborated the fact that the hydrological changes are the integrated consequences of various external factors, basically the human activities and climate changes. Generally, decreasing annual maximum water (AMW) level was observed mainly in the seaward regions characterized by decreasing occurrence frequency of higher AMW level. Streamflow variations are influenced mainly by precipitation changes. Increasing annual maximum streamflow (AMS) can be attributed to the increasing precipitation intensity in recent years. However, in the East River basin, hydrological regulation function of the water reservoirs greatly reduced the AMS. In the lower East River, however, downcutting river channel and notable increases in the cross-section area caused larger magnitude of decrease in AMW level when compared to AMS. The time when the relations between AMW level and streamflow start to change matches well the time when massive in-channel sand dredging occurred, showing tremendous influences of human activities on hydrological processes in the lower Pearl River basin. This study will be of great scientific and practical merits in better understanding the statistical behaviours of hydrological extremes under the changing environment and also help to improve human mitigation to natural hazards in south China. Copyright © 2010 John Wiley & Sons, Ltd.

Description: Employing long-range correlation, complexity features and clustering, this study investigated the influence of dam and lake-river systems on the Yangtze River flow. The impact of the Gezhouba Dam and the lake systems on streamflow was evaluated by analysing daily streamflow records at the Cuntan, the Yichang and the Datong station. Results indicated no evident influence of the Gezhouba Dam on streamflow changes. Distinct differences in scaling behaviour, long-range correlation and clustering of streamflow at the Datong station when compared with those at the Cuntan and Yichang stations undoubtedly showed the influence of water storage and the buffering effect of the lake systems between the Datong station and other two hydrological stations on streamflow in the lower Yangtze River basin. Decreased regularity, enhanced long-range correlation and increased clustering of streamflow in the lower Yangtze River basin due to the effect of water storage of the lake systems were corroborated. © 2011 John Wiley & Sons, Ltd.

Description: Observed rainfall and flow data from the Dongjiang River basin in humid southern China were used to investigate runoff changes during low-flow and flooding periods and in annual flows over the past 45 years. We first applied the non-parametric Mann-Kendall rank statistic method to analyze the change trend in precipitation, surface runoff and pan evaporation in those three periods. Findings showed that only the surface runoff in the low-flow period increased significantly, which was due to a combination of increased precipitation and decreased pan evaporation. The Pettitt-Mann-Whitney statistical test results showed that 1973 and 1978 were the change points for the low-flow period runoff in the Boluo sub-catchment and in the Qilinzui sub-catchment, respectively. Most importantly, we have developed a framework to separate the effects of climate change and human activities on the changes in surface runoff based on the back-propagation artificial neural network (BPANN) method from this research. Analyses from this study indicated that climate variabilities such as changes in precipitation and evaporation, and human activities such as reservoir operations, each accounted for about 50% of the runoff change in the low-flow period in the study basin. Copyright © 2010 John Wiley & Sons, Ltd.

Description: Variations in streamflows of five tributaries of the Poyang Lake basin, China, because of the influence of human activities and climate change were evaluated using the Australia Water Balance Model and multivariate regression. Results indicated that multiple regression models were appropriate with precipitation, potential evapotranspiration of the current month, and precipitation of the last month as explanatory variables. The NASH coefficient for the Australia Water Balance Model was larger than 0.842, indicating satisfactory simulation of streamflow of the Poyang Lake basin. Comparison indicated that the sensitivity method could not exclude the benchmark-period human influence, and the human influence on streamflow changes was overestimated. Generally, contributions of human activities and climate change to streamflow changes were 73.2% and 26.8% respectively. However, human-induced and climate-induced influences on streamflow were different in different river basins. Specifically, climate change was found to be the major driving factor for the increase of streamflow within the Rao, Xin, and Gan River basins; however, human activity was the principal driving factor for the increase of streamflow of the Xiu River basin and also for the decrease of streamflow of the Fu River basin. Meanwhile, impacts of human activities and climate change on streamflow variations were distinctly different at different temporal scales. At the annual time scale, the increase of streamflow was largely because of climate change and human activities during the 1970s–1990s and the decrease of streamflow during the 2000s. At the seasonal scale, climate change was the main factor behind the increase of streamflow in the spring and summer season. Human activities increase the streamflow in autumn and winter, but decrease the streamflow in spring. At the monthly scale, different influences of climate change and human activities were detected. Climate change was the main factor behind the decrease of streamflow during May to June and human activities behind the decrease of streamflow during February to May. Results of this study can provide a theoretical basis for basin-scale water resources management under the influence of climate change and human activities. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Description: Using the multi-scale entropy analysis (MSE), we study the effects of water reservoirs on the river flow records based on long streamflow series covering January 1, 1954 and December 31, 2009 at four representative hydrological stations, i.e. the Longchuan, the Heyuan, the Lingxia and the Boluo stations. Hydrological effects of two major water reservoirs, the Xinfengjiang and the Fengshuba water reservoirs, are evaluated. The results indicate that: (1) before the construction of the water reservoirs, the complexity of the streamflow series comes to be decreasing from the upper to the lower East River and which should be attributed to the topographical properties and buffering effects of the river channel; (2) construction of water reservoirs greatly increases the complexity degree of the hydrological processes, and this influence is subjected to a damping process with the increase of distance between the water reservoirs and the hydrological stations; (3) power generation is the major function of the water reservoirs in the East River basin. The results of this study should be of theoretical and scientific merits in terms of conservation of the ecological environment and also water resources management under the influences of climate changes and intensifying human activities. © 2011 John Wiley & Sons, Ltd.