Taoyuan Wei

The drivers of risk to water security in Shanghai

Big cities are often said to have big water problems, and Shanghai is no exception. In this paper, we examine and compare the influence of the major factors that give rise to the risk of water insecurity in Shanghai. There is an extensive and diverse literature on these issues, dealt with in isolation, and here, we provide a synthesis of the literature, together with our own assessments and calculations, to assess what are the risks to Shanghai’s water supply and what is our degree of confidence in this assessment. We describe the systems that supply water to the city, and past and future changes in the systems, including changes in the glaciers that supply some water to the river, changes in climate, changes in land use, the construction of dams, and water diversions. We show how, at the same time as Shanghai is increasing its dependence on the Yangtze river, water diversions and sea level rise are increasing the risk that this water will be too saline to consume at certain times of the year. This analysis suggests that most of the major drivers of the risk to water security in Shanghai are within the power of environmental managers to control.

Constructing Water Shortages on a Huge River: The Case of Shanghai

Abstract Shanghai is located on the world’s third largest river (by volume).Yet it faces therisk of shortages of drinking water. Many decisions and environmental charac-teristics have contributed to this threat. First, Shanghai has become dependent onwater brought into the municipality by rivers. Second, it has become increasinglyreliant on water from the Changjiang (Yangzi River), principally in order tocontrol the levels of pollution in the water that enters its treatment plants. Third,for reasons associated with inter-provincial administrative arrangements, thecity’s water intakes are located within the municipality, within the estuary zoneand subject to tidal intrusions of salt water. Fourth, at high tide and when theChangjiang’s discharge is low, salt intrudes far into the estuary, beyond thecurrent water intakes. If sea levels rise, these intrusions will become more pro-nounced. Fifth, large-scale central government infrastructure projects (such asdams and the South-North Transfer) are altering the hydrological characteristicsof the river. Such projects raise the probability of salt water intrusions into thewater intake zone. The Shanghai and central governments have thus made a seriesof decisions that, taken together, have led the municipality to rely on a source ofdrinking water that is increasingly unreliable and subject to the risk of shortagesdue to salt water intrusions. Why these decisions have been made – independently– is an important problem for those who would understand the provision of waterfor cities and the practical efficacy of Chinese governance systems.KEY WORDS

Provenance discrimination of the clay sediment in the western Taiwan Strait and its implication for coastal current variability during the late-Holocene

This study aims to quantify the contribution of Yangtze clays to the sediment accumulation in the western Taiwan Strait and reconstruct the strength of Chinese Coastal Current (CCC) since middle-Holocene driven by East Asian Winter Monsoon (EAWM). Both down-core and surficial sediment samples were collected for grain size, radiocarbon, and clay mineral analyses. One 250-cm-long core was collected from the southern Yangtze distal mud wedge in western Taiwan Strait which receives Yangtze-derived clays transported by the Zhejiang-Fujian Coastal Current (ZFCC), the southern part of CCC. Clay minerals were examined in surficial sediment samples which were influenced by the Yangtze, Zhejiang-Fujian, western Taiwanese rivers, and the inner-shelf mud wedge. Ternary diagrams of smectite–kaolinite–chlorite revealed that three endmembers represented the Yangtze, Min, and western Taiwanese rivers, respectively. The estuaries seaward of the tidal current limits of Zhejiang-Fujian rivers, especially the Qiantang and Ou, were influenced by Yangtze-derived sediments through energetic tidal mixing. It was found that smectite can be used as a fingerprint of the Yangtze fine-grained sediment because among all the studied rivers, the Yangtze is the only one supplying smectite. Clay mineral results in core sediments revealed a dramatic provenance change at the depth of 113 cm, dated at ~4.0 cal. kyr BP. Smectite disappeared in the upper core, suggesting decreased contribution of Yangtze clays to the southern distal mud wedge. Decreased grain size of the fine population in the upper core also indicated that the ZFCC weakened during the late-Holocene. Such a decline also occurred in Subei Coast Current (northern part of CCC), revealed by the previous studies. The decline of CCC was related to the decreased EAWM of the late-Holocene, and it resulted in decreased sediment accumulation rate of the inner-shelf mud.

Spatial and temporal distribution of trace elements in Yangtze Estuary, China: Significance of diluted setting

The present study is to examine the spatial and temporal distribution of eight trace elements (Sr, Ba, B, Ga, Ni, V, Cu, and F) in various Holocene marine subfacies in the Yangtze Estuary, including its subaqueous delta by sediment borehole and vibrocore. Results demonstrate that grain size is the determinant factor in controlling the concentration of most trace elements discussed. Prodelta mud that occurs usually below the normal wave base can serve as a depository sink for trapping trace elements over the long-term time period. For example, copper concentration is 5–6 times higher than those found in the estuarine sediment. Boron, which is used to be a salinity indicator, shows a strong negative correlation with paleosalinity (using sediment phosphate method), implying desalinized water setting in the Yangtze Estuary, into which a large quantity of the Yangtze freshwater (924 ×109 m3/a) has discharged. Trace element concentrations of the study area were compared with those collected from the middle and lower Yangtze River reaches, and from the east China continental shelf, including the Okinawa Trough. Result tends to show a terrigenous derivation of most geochemical components of the study area. Concentrations of strontium and barium are correlated with an increase in distance away from the estuary, rather than affected by grain size. Variation of trace elements in downcore Holocene sediment sections are fairly consistent with concentrations revealed by the modern vibrocore transect that extends from nearshore delta front, to offshore prodelta and to the delta-shelf transit zone. The overall distribution of geochemical elements discussed is capable of environmental implication to characterize the Yangtze estuarine transit between land and sea.

Erratum to: Estimating urban water demand under conditions of rapid growth: the case of Shanghai

• On page 4 the first line in the first paragraph should read as follows: of 4.10 9 10 m a. These are located in remote and rural. • On page 4 the second line in the second paragraph should read as follows: supplied 3.12 9 10 m a in 2013, and which are mostly. • On page 4 the numbers on the y axes of both Fig. 1a, b should be reduced by a factor of 10. • On page 4 lines 11 to 16 in the third paragraph should read as follows: period 1978–2013 increased from 0.97 9 10 m a to 3.10 9 10 m a; of this, the water for residential and public open space increased from 0.36 9 10 m a to 1.97 9 10 m a, a fivefold increase and therefore a rate obviously greater than that of industrial water (0.62–1.15 9 10 m a over the same period) (Fig. 1a). • On page 4 lines 20 and 21 in the third paragraph should read as follows: water pumping grew from 1.17 9 10 m a in 1978 to 4.10 9 10 m a in 2013 (Fig. 1b). • On page 6 the numbers on the y axis of Fig. 5 should be reduced by a factor of 10. The online version of the original article can be found under doi:10.1007/s10113-016-1100-6.