Xixi Lu
Email Address
geoluxx@nus.edu.sg
196 results
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Publication Retrieval of suspended sediment concentrations in the turbid water of the Upper Yangtze River using Landsat ETM+(2007) Wang, J.; Lu, X.; Zhou, Y.; GEOGRAPHYPublication Abrupt changes in the discharge and sediment load of the Pearl River, China(2012-05-15) Zhang, Q.; Xu, C.-Y.; Chen, X.; Lu, X.; GEOGRAPHYThe 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.Publication Shifted sediment-transport regimes by climate change and amplified hydrological variability in cryosphere-fed rivers(AMER ASSOC ADVANCEMENT SCIENCE, 2023-11-10) Zhang, Ting; Li, Dongfeng; East, Amy E; Kettner, Albert J; Best, Jim; Ni, Jinren; Lu, Xixi; Prof Xixi Lu; GEOGRAPHYClimate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pluvial, and mixed regimes, respectively. Spring sees a shift toward pluvial-dominated sediment transport due to less snowmelt and more erosive rainfall. Summer is characterized by intensified glacier meltwater pulses and pluvial events that exceptionally increase sediment fluxes. Our study highlights that the increases in hydroclimatic extremes and cryosphere degradation lead to amplified variability in fluvial fluxes and higher summer sediment peaks, which can threaten downstream river infrastructure safety and ecosystems and worsen glacial/pluvial floods. We further offer a monthly-scale sediment-availability-transport model that can reproduce such regime shifts and thus help facilitate sustainable reservoir operation and river management in wider cryospheric regions under future climate and hydrological change.Publication Remote sensing estimation of suspended sediment concentrations in highly turbid inland river waters: An example from the lower Jinsha tributary, Yunnan, China.(International Center for Remote Sensing of Environment, 2003) Liew, S. C; Lu, X. X; Chen, P; Zhou, Y.; GEOGRAPHY; CTR FOR REM IMAGING,SENSING & PROCESSINGPublication Larger Asian rivers: Shorter and longer term hydro-climate changes in humid and arid environments(Elsevier Ltd, 2014) Lu X.; Jiang T.; GEOGRAPHYPublication Redressing China's Strategy of Water Resource Exploitation(2013-03) Ran, L.; Lu, X.X.; GEOGRAPHYChina, with the confrontation of water-related problems as an element of its long history, has been investing heavily in water engineering projects over the past few decades based on the assumption that these projects can solve its water problems. However, the anticipated benefits did not really occur, or at least not as large as expected. Instead, the results involved additional frustrations, such as biodiversity losses and human-induced disasters (i.e., landslides and earthquakes). Given its inherent shortcomings, the present engineering-dominated strategy for the management of water resources cannot help solve China's water problems and achieve its goal of low-carbon transformation. Therefore, the present strategy for water resources exploitation needs to be reevaluated and redressed. A policy change to achieve better management of Chinese rivers is urgently needed. © 2013 Springer Science+Business Media New York.Publication Application of remote sensing in flood management with special reference to monsoon Asia: A review(2004) Sanyal, J.; Lu, X.X.; GEOGRAPHYPublication Sediment load(CRC Press, 2008) Lu, X.X.; Higgitt, D.L.; GEOGRAPHYPublication MODIS-based remote sensing of suspended sediment concentrations of the Middle and Lower Yangtze River, China(IAHS Press, 2012) Lu X.-X.; Wang J.-J.; Liu C.; GEOGRAPHYPublication Physically controlled CO2 effluxes from a reservoir surface in the upper Mekong River Basin: A case study in the Gongguoqiao Reservoir(Copernicus GmbH, 2019) Lin, L.; Lu, X.; Liu, S.; Liong, S.-Y.; Fu, K.; TROPICAL MARINE SCIENCE INSTITUTE; GEOGRAPHYImpounding alters the carbon transport in rivers. To quantify this effect, we measured CO2 effluxes from a mountainous valley-type reservoir in the upper Mekong River (known as Lancang River in China). CO2 evasion rates from the reservoir surface were 408-337 mgCO2 m-2 d-1 in the dry season and 305-262 mgCO2 m-2 d-1 in the rainy season much lower than those from the riverine channels (1567-2312 mgCO2 m-2 d-1 at the main stem and 905-1536 mgCO2 m-2 d-1 at the tributary). Low effluxes in the pelagic area were caused by low allochthonous organic carbon (OC) inputs and photosynthetic uptake of CO2. A negative relationship between CO2 efflux and water temperature suggested CO2 emissions at the pelagic area were partly offset by photosynthesis in the warmer rainy season. CO2 emissions from the reservoir outlet and littoral area, which were usually considered hotspots of CO2 emissions, had a low contribution to the total emission because of epilimnion water spilling and a small area of the littoral zones. Yet at the river inlets effluxes were much higher in the dry season than in the rainy season because different mixing modes occurred in the two seasons. When the river joined the receiving waterbody in the dry season, warmer and lighter inflow became an overflow and large amounts of CO2 were released to the atmosphere as the overflow contacted the atmosphere directly. Extended water retention time due to water storage might also help mineralization of OC. In the wet season, however, colder, turbid and heavier inflow plunged into the reservoir and was discharged downstream for hydroelectricity, leaving insufficient time for decomposition of OC. Besides, diurnal efflux variability indicated that the effluxes were significantly higher in the nighttime than in the daytime, which increased the estimated annual emission rate by half. © Author(s) 2019.