Impact of the Three Gorges Dam, the South–North Water Transfer Project and water abstractions on the duration and intensity of salt intrusions in the Yangtze River estuary

Abstract

This paper assesses the impacts of the Three Gorges Dam, the South-North Water Transfer Project and other water abstractions on the probability of long-duration salt intrusions into the Yangtze River estuary. Studies of intrusions of saltwater into estuaries are typically constrained by both the short duration of discharge records and the paucity of observations of discharge and salinity. Thus, studies of intrusions of saltwater into estuaries typically seek to identify the conditions under which these intrusions occur, using detailed observations for periods of 20-60 days. The paper therefore first demonstrates a method by which to identify the conditions under which intense intrusions of longduration occur and then applies that method to analyse the effect of the three projects. The paper constructs a model of the relationship between salinity and discharge and then employs Monte Carlo simulation methods to reconstruct the probability of observing intrusions of differing intensities and durations in relation to discharge. The model predicts that the duration of intrusions with chlorinity ≥ 250 mg L −1 (or ≥ 400 or 500 mg L −1 ) increases as the number of consecutive days with discharge ≤ 12 000 m 3 s −1 (or ≤ 8000 m 3 s −1 ) increases. The model predicts that in 1950-2014, the number of consecutive days with chlorinity ≥ 250 mg L −1 averaged 21.34 yr −1 ; if the three projects operate according to their normal rules, that average would rise to 41.20 yr −1 . For a randomly selected year of discharge history from the period 1950-2014, under normal operating rules for these projects the probability of an intrusion rises from 0.25 (for 30-day intrusions) or 0.05 (for 60-day intrusions) to 0.57 or 0.28, respectively.

A Review of the Economic, Social, and Environmental Impacts of China’s South–North Water Transfer Project: A Sustainability Perspective

“…Early reviews noted that decreased flow in the Yangtze Basin could worsen the already existing problem of estuary salinization (e.g., [3,9]). These findings were confirmed by Chen et al [11] who found that the ER-SNWTP alone could increase estuary salinization between January and February, as well as Webber et al [37] who carried out a broader analysis of Yangtze Estuary salinization. A similar pattern connects the water losses caused by MR-SNWTP to riparian health along the Han River, from which the MR-SNWTP originates [13,38].…”

“…The Han River will experience declines in discharge [13], while the communities who rely on it will continue to grow and demand more water. Yangtze Estuary salinization will grow worse, especially during dry months and years, further increasing the environmental concerns in this already critical region [11,37]. Although the contention that, on balance, the socio-ecological costs in water-providing areas will be outweighed by the benefits in water-receiving areas on a national scale (e.g., [25]) seems plausible, these aggregate effects are likely of little consolation to those who will be negatively impacted by the implementation of this program.…”

Restore or retreat? saltwater intrusion and water management in coastal wetlands

“…, Hutchinson , Webber et al. ) illustrate the potential for saltwater barrier removal to alleviate this effect.…”

An integrated assessment of China's South—North Water Transfer Project

“…Early research on China's SNWTP focused primarily on its economic viability and projected social and environmental effects (Wilson et al, 2017, have a full review), while in recent years, there have been two primary lines of enquiry in English language publications. The second line of enquiry concerns the SNWTP's physical impacts, primarily the modelling or direct measurement of hydrological impacts (see Ma et al, 2016;Webber et al, 2015;Yan et al, 2012;Ye et al, 2015) and pollution flows (Zhang et al, 2018). While these studies do point to the far-reaching and unequal social, economic, political, and environmental effects of the SNWTP, particularly in source regions, their focus is the power struggles embedded in the SNWTP.…”

“…While these studies do point to the far-reaching and unequal social, economic, political, and environmental effects of the SNWTP, particularly in source regions, their focus is the power struggles embedded in the SNWTP. The second line of enquiry concerns the SNWTP's physical impacts, primarily the modelling or direct measurement of hydrological impacts (see Ma et al, 2016;Webber et al, 2015;Yan et al, 2012;Ye et al, 2015) and pollution flows (Zhang et al, 2018). There is limited dialogue between those undertaking such approaches, and as a result, no integrated account of the geographic implications, both human and physical, of this massive interbasin transfer.…”