This paper presents a brief review of the South to North Water Diversion Project (STNWDP) in China. Basic information about the geography, climate, water resource, water pollution and social situation are provided in order to understand the decision by the Chinese government on the expedited implementation of the STNWDP. The potential problems associated with the STNWDP are discussed. It is proposed that the ultimate objective is to help improve the water environment in north China, rather than to simply meet the ever-increasing water demand and to produce more sewage, and that water price, investment policy and engineering operations are important for achieving this objective. Legislation is needed in the long run because this project involves a large number of districts. The STNWDP, together with global climate warming, will enlarge the temporal variability of water discharge from the Yangtze into the sea and therefore have far-reaching effects on the freshwater resource in areas around the Yangtze delta.
Deltaic channels are significant landforms at the interface of sediment transfer from land to oceanic realms. Understanding the dynamics of these channels is urgent because delta processes are sensitive to climate change and adjustments in human activity. To obtain a better understanding of the morphological processes of large deltaic channels, this study assessed the evolution and response mechanism of the South Channel and South Passage (SCSP) in the Yangtze Estuary between 1983 to 2018 using hydrology, multibeam echo sounding and historical bathymetry datasets. Decadal changes in riverbed volume and erosion/deposition patterns in the SCSP were assessed. The results showed that the SCSP experienced substantial deposition with a total volume of 26.90 × 107 m3 during 1983–2002, but significant bed erosion with a total volume of 26.04 ×107 m3 during 2003–2010. From 2011 to 2018, the estuarine riverbeds shifted from erosive to depositional, even though the deposition was relatively marginal (0.76 ×107 m3). We inferred that the SCSP have most likely changed from a net erosion phase to a deposition stage in response to local human activities including sand mining, river regulation project, and Deep Water Channel Regulation Project). The channel aggradation will possibly continue considering sea level rise and the ongoing anthropogenic impacts. This is the first field evidence reporting that the lowermost Yangtze River is reaching an equilibrium state in terms of channel erosion and, in fact, the Yangtze River Estuary channels are beginning to aggrade. The findings have relevant implications for the management of the Yangtze River and other lowland alluvial rivers in the world as global sea level continues rising and human intervention on estuarine systems persists.
Abstract In some cases of imaging, wide spatial range and high spatial resolution are both required, which requests high performance of detection devices and huge resource consumption for data processing. We propose and demonstrate a multi-scale adaptive imaging method based on the idea of computational ghost imaging, which can obtain a rough outline of the whole scene with a wide range then accordingly find out the interested parts and achieve high-resolution details of those parts, by controlling the field of view and the transverse coherence width of the pseudo-thermal field illuminated on the scene with a spatial light modulator. Compared to typical ghost imaging, the resource consumption can be dramatically reduced using our scheme.
Abstract A diagnostic study on the large and episodic decrease of discharge from the Yangtze River to the sea is presented. No trend has been detected so far in the time series of river flow recorded at Datong, but a large and short-term drop is evident through analysing the yearly minimum discharges. Water abstractions in the middle reach are evidently responsible for the large and episodic drop recorded at Datong. Downstream of Datong the discharge further decreases due to water abstraction by sluices and pumping stations, with a capacity comparable to the average discharge from Datong in dry months. Such large-scale water diversions may greatly reduce the water discharge into the sea during droughts, if countermeasures are not prepared. An increasing seasonal variability will exacerbate the existing water and environmental problems in the Yangtze Delta and estuary. An integrated management system is necessary for sustaining sufficient freshwater discharge into the sea. Résumé Une recherche diagnostique a été menée au sujet de la baisse importante et épisodique du débit du Fleuve Yangtze déversé en mer. Jusqu'à présent, aucune tendance n'a été détectée dans des séries temporelles de débit à Datong, mais l'analyse des débits minimum annuels montre l'existence d'une baisse importante et brève, dont les prélèvements d'eau sont évidemment responsables. Le débit continue de baisser en aval de Datong à cause des prélèvements des canaux et des stations de pompage, don't l'ampleur est équivalente au débit moyen des mois secs. Ces prélèvements d'eau à grande échelle peuvent lourdement réduire le débit arrivant à la mer lors des sécheresses, si des mesures palliatives ne sont pas mises en œuvre. L'augmentation de la variabilité saisonnière va mettre plus encore en péril les ressources en eau et les écosystèmes dans le delta et l'estuaire du Yangtze. Il est donc nécessaire d'avoir une gestion intégrée pour maintenir un débit d'eau douce déversé en mer suffisant. Key words: Yangtze Riverriver runoffwater diversionsstreamflow droughtstrend detectionHow regimesMots clefs: Fleuve Yangtzeécoulement de cours d'eauprélèvement d'eauétiagesdétection de tendancerégimes hydrologiques
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