| 1. |
- Chen, David, et al.
(författare)
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CHANGE-POINT ALTERATIONS OF EXTREME WATER LEVELS AND UNDERLYING CAUSES IN THE PEARL RIVER DELTA, CHINA
- 2009
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Ingår i: Rivers Research and Applications. - : Wiley. - 1535-1459 .- 1535-1467. ; 25, s. 1153-1168
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the Bayesian model and Lepage test were used to detect change point and to analyse associated statistical properties of high/low water levels in summer (June, July and August (JJA)) and winter (December, January and February (DJF)) months across the PRD (Pearl River Delta). The results indicate that: (1) two time intervals, that is 1979-1981 and 1988-1995, witness abrupt changes of SmH/SmL (summer mean high water level/summer mean low water level). The lower PRD is dominated by increased mean and coefficient of variation (Cv) of SmH. Increased mean but decreased Cv of SmL can be observed in the Mainstem Pearl River; (2) WmL (winter mean low water level) and WmH (winter mean high water level) of about 74% of the total stations have two change points occurred roughly during 1969-1971 and 1993-1995. First change points of WmH are mainly characterized by increased mean and Cv, but decreased mean and increased Cv of WmL can be observed across major parts of the PRD. The driving factors causing abrupt changes of water levels are various. Intensive human activities cannot be ignored, for example in-channel dredging and reallocation of the streamflow within the river channels due to human-induced topographical changes of river channel. Different responses of high/low water levels to externally influencing factors and interactions between influencing factors make the alterations of the water levels across the PRD more complicated. The findings of this paper will be helpful for the management of the PRD and human mitigation to natural hazards under the changing environment. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 2. |
- Xie, F., et al.
(författare)
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Cross-cultural adaptation and validation of Singapore English and Chinese versions of the Knee injury and Osteoarthritis Outcome Score (KOOS) in Asians with knee osteoarthritis in Singapore
- 2006
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Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 14:11, s. 1098-1103
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To cross-culturally adapt and validate Singapore English and Chinese versions of the Knee injury and Osteoarthritis Outcome Score (KOOS) in patients with knee osteoarthritis (OA) in Singapore. Methods: Singapore English and Chinese versions were cross-culturally adapted from the source English KOOS following standard guidelines (including cognitive debriefing). Patients were asked to complete identical questionnaires containing the KOOS, Short Form 36 Health Survey, and EQ-5D twice within 6 days. Reliability was assessed using Cronbach's alpha and intraclass correlation coefficients (ICC), dimensionality using item-to-domain correlations and convergent and divergent construct validity using 14 and 13 a priori hypotheses, respectively. Results: Singapore English and Chinese KOOS versions were well accepted by patients in pilot testing and were therefore administered to a consecutive sample of 127 English and 131 Chinese-speaking Singaporeans with knee OA. Cronbach's alpha exceeded 0.7 for all domains except for Chinese pain and symptoms domains. ICC exceeded 0.7 for all domains except for English sport and recreation and Chinese knee-related QoL domains. Hypothesized item-to-domain correlations (Spearman's rho >= 0.4) were observed for 38 items in English and 29 in Chinese versions. Convergent construct validity was supported by the presence of hypothesized moderate/strong correlations (rho = 0.37-0.65) for 13 and 11 a priori hypotheses in the English and Chinese KOOS, respectively. Divergent construct validity was supported by the presence of weak correlations (rho = 0.02-0.34) for 12 and 11 a priori hypotheses in the English and Chinese KOOS, respectively. Conclusion: The Singapore English and Chinese KOOS were well accepted and demonstrated acceptable reliability and validity in Asian patients with knee OA in Singapore. (C) 2006 OsteoArthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
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| 3. |
- Yang, Tao, et al.
(författare)
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A spatial assessment of hydrologic alteration caused by dam construction in the middle and lower Yellow River, China
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 22:18, s. 3829-3843
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Tidskriftsartikel (refereegranskat)abstract
- The ‘range of variability approach’ (RVA) and mapping technique are used to investigate the spatial variability of hydrologic alterations (HA) due to dam construction along the middle and lower Yellow River, China, over the past live decades. The impacts of climate variability oil hydrological process have been removed during wet and dry periods and the focus IS Oil the impacts of human activities, Such as dam construction, on hydrological processes. Results indicate the following: (1) The impacts of the Sanmenxia reservoir oil the hydrologic alteration are relatively slight with a mean HA value of 0.48, ranking in the last place among the four large reservoirs. (2) Xiaolangdi reservoir has significantly changed the natural flow regime downstream with mean HA value of 0.56, ranking it in first place among the large reservoirs. (3) The results of ranked median degrees of 33 hydrologic alteration indicators for 10 stations in the Yellow River show that the hydrologic alteration of Huayuankou ranks the highest among 10 stream gauges. (4) Impacts of reservoirs on hydrological processes downstream of the dams are closely associated with the regulating activities of the reservoirs. At the same time, alterations of streamflow regimes resulting from climatic changes (e.g. precipitation variability) make the situation more complicated and more hydrological observations will be necessary for further analysis. The results of the current study will be greatly beneficial to the regional water resources management and restoration of eco-environmental systems in the middle and lower Yellow River characterized by intensified dam construction under a changing environment. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 4. |
- Yang, Tao, et al.
(författare)
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Spatio-temporal changes of hydrological processes and underlying driving forces in Guizhou region, Southwest China
- 2009
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 23:8, s. 1071-1087
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the changes in streamflow and associated driving forces is crucial for formulating a sustainable regional water resources management strategy in the environmentally fragile karst area of the southwest China. This study investigates the spatio-temporal changes in streamflow of the Guizhou region and their linkage with meteorological influences using the Mann-Kendall trend analysis, singular-spectrum analysis (SSA), Lepage test, and flow duration curves (FDCs). The results demonstrate that: (1) the streamflow in the flood-season (June-August) during 1956-2000 increased significantly (confidence level a parts per thousand yen95%) in most catchments, closely consistent with the distinct increasing trend of annual rainfall over wet-seasons. The timings of abrupt change for streamflow in most catchments are found to occur at 1986; (2) streamflow in the Guizhou region experiences significant seasonal changes prior/posterior to 1986, and in most catchments the coefficient of variation of monthly streamflow increases; (3) spatial changes in streamflow indicate that monthly streamflow in the north-west decreases but increases in other parts; (4) the spatial high- and low-flow map (Q (5) and Q (95)) reveals an increase in the extremely large streamflow in the five eastern catchments but a decrease in the extremely low streamflow in the four eastern catchments and three western catchments during 1987-2000. An increase in streamflow, particularly extreme flows, during the flood season would increase the risk of extreme flood events, while a decrease in streamflow in the dry season is not beneficial to vegetation restoration in this ecologically fragile region.
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| 5. |
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| 6. |
- Zhang, Qiang, et al.
(författare)
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Multiscale variability of sediment load and streamflow of the lower Yangtze River basin : Possible causes and implications
- 2009
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 368, s. 96-104
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Tidskriftsartikel (refereegranskat)abstract
- Long monthly streamflow and sediment load series observed at the Datong station located in the lower Yangtze River basin were analyzed using the scanning t-test, F-test and coherency analysis techniques. The results indicated that: (1) different changing properties of the first and the second moments of the hydrological series on different time scales were observed, reflecting different driving factors influencing the hydrological processes of the lower Yangtze River basin; (2) a generally decreasing trend can be identified after the mid-1980s. Significant abrupt changes in sediment load were analyzed in the sediment load series. However, more complicated changing patterns can be observed in the changes in streamflow. Generally decreasing sediment load and increasing streamflow gave rise to anti-phase relations between sediment load and the streamflow on longer time scales. In-phase relations between sediment load and streamflow, on shorter time scales may imply a considerable influence of the hydrological dynamics on sediment transport; and (3) human activities, particularly the construction of water storage reservoirs, exerted a massive influence on sediment load variations. Construction of a large amount of water reservoirs on the tributaries of the Yangtze River and the Gezhouba Dam on the mainstem of the Yangtze River seem to be the main factors responsible for abrupt changes in the sediment load. Construction of the Three Gorges Dam causes a sharp decrease and unstable variability in sediment load variations, which may pose new challenges for the ecological environment conservation and the deltaic management of the Yangtze Delta region. (c) 2009 Elsevier B.V. All rights reserved.
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| 7. |
- Zhang, Qiang, et al.
(författare)
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Scaling properties of the runoff variations in the arid and semi-arid regions of China : a case study of the Yellow River basin
- 2009
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 23:8, s. 1103-1111
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Tidskriftsartikel (refereegranskat)abstract
- We analyzed long daily runoff series at six hydrological stations located along the mainstem Yellow River basin by using power spectra analysis and multifractal detrended fluctuation analysis (MF-DFA) technique with aim to deeply understand the scaling properties of the hydrological series in the Yellow River basin. Research results indicate that: (1) the runoff fluctuations of the Yellow River basin exhibit self-affine fractal behavior and different memory properties at different time scales. Different crossover frequency (1/f) indicates that lower crossover frequency usually corresponds to larger basin area, and vice versa, showing the influences of river size on higher frequency of runoff variations. This may be due to considerable regulations of river channel on the runoff variations in river basin of larger basin size; (2) the runoff fluctuations in the Yellow River basin exhibit short-term memory properties at smaller time scales. Crossover analysis by MF-DFA indicates unchanged annual cycle within the runoff variations, implying dominant influences of climatic changes on changes of runoff amount at longer time scales, e.g. 1 year. Human activities, such as human withdrawal of freshwater and construction of water reservoirs, in different reaches of the Yellow River basin may be responsible for different scaling properties of runoff variations in the Yellow River basin. The results of this study will be helpful for hydrological modeling in different time scales and also for water resource management in the arid and semi-arid regions of China.
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| 8. |
- Zhang, Qiang, et al.
(författare)
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Spatial assessment of hydrologic alteration across the Pearl River Delta, China, and possible underlying causes
- 2009
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 23:11, s. 1565-1574
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Tidskriftsartikel (refereegranskat)abstract
- The alterations of the water level across the Pearl River Delta (PRD) were investigated Using a ‘range of variability approach’ (RVA) based on monthly water level datasets extracted from 17 gauging stations. A mapping method was used to illustrate the spatial patterns in the degrees of alteration of water levels. The results indicated that more stations showing moderate and high alterations in monthly mean maximum and minimum water levels when compared with monthly maximum and minimum water levels. River channels characterized by higher alterations of water levels were observed mainly in the regions north of 22 degrees 30’N. Alterations of water levels across the PRD were a consequence of various influencing factors. However, changed hypsography due to extensive and intensive human activities, particularly the large-scale dredging and excavation of the river sand, may be taken as one of the major causes for the substantial hydrologic alteration. This Study indicated that the river channels characterized by altered water levels are mostly those characterized by highly and moderately intensive sand dredging. The changed ratio of the streamflow between Makou and Sanshui stations, the major upstream flow control stations, also influenced the water level alterations of the Pearl River delta. The results of this study will be of great significance in water resources management and better human mitigation of the natural hazards due to the altered Water level under the changing environment. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 9. |
- Zhang, Qiang, et al.
(författare)
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Variability of Water Resource in the Yellow River Basin of Past 50 Years, China
- 2009
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Ingår i: Water resources management. - : Springer Science and Business Media LLC. - 0920-4741 .- 1573-1650. ; 23:6, s. 1157-1170
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Tidskriftsartikel (refereegranskat)abstract
- We use Mann-Kendall trend test and Lepage method to study spatial and temporal variations of the streamflow series over the past 50 years based on daily hydrologic data from six gauging stations in the Yellow River basin. Research results indicate that: (1) The streamflow of the Yellow River basin is decreasing and water resource deficit tends to be more serious from the upper to the lower Yellow River basin; (2) Zero-flow days are observed after 1970 and overwhelmingly prevail during 1990-2000. Moreover, zero-flow events are observed mainly during spring and summer; (3) Low flow events are more sensitive to climatic changes and human activities when compared to the high flow events, which is mainly reflected by larger fluctuation of timing of change points. Furthermore, the timing of change point of hydrologic events tends to be earlier from the upper to the lower Yellow River basin, indicating more intensive impacts of human activities on water resource in the lower Yellow River basin. The current research will be greatly helpful for sound and effective water resource management in the Yellow River basin, being characterized by serious water deficit.
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