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With population increase and economic growth, the flow regime of the Yangtze River has been altered to some extent by human activities, particularly dam construction. Dam-induced alterations in the flow regime of the Yangtze River will unavoidably influence water allocation among different water users and instream ecological water requirements may not be guaranteed during some months, particularly during phases of reservoir storing water. To assess the impacts of the Three Gorges reservoir operation on the downstream minimum instream ecological water requirements, this paper selected the Three Gorges reservoir and Yichang hydrological station below the reservoir as case study sites. On the basis of long-term time series of daily discharge data, the reservoir outflow was simulated under two water storing schemes and the degree to which the downstream minimum ecological flow was satisfied was computed. The results of this paper could provide references for the integrated management of the Yangtze River water resources and the assessment of dam-induced impacts on the Yangtze River ecosystem health. [ABSTRACT FROM AUTHOR]

Channel morphology in an alluvial river usually varies due to the altered flow and sediment regime from upstream damming. This paper reports an evaluation of the dynamical changes of sedimentation and erosion in the middle and lower reaches of the Yangtze River after operation of the Three Gorges Dam (TGD). Here, we present the results from a case study of the Shashi Reach in the middle Yangtze River, which is the first sandy-bed and meandering reach downstream of TGD. Databases were constructed using a digital elevation model of channel topography based on the 1:10,000 topographic maps from the 1980s to 2012 and hydrological records from 1956 to 2013. Results indicate that the erosion in the Shashi Reach was mainly confined to the deeper channel and that it has increased since the construction of the TGD. No significant changes were observed above the bank-full level, resulting in the decrease of the width-to-depth ratio. These changes may be principally caused by variations of the seasonal distribution of flow and sediment due to the operation of the dam. In addition, results show that the cross-sectional shape change of the channel is related to the relative erodibility of the channel bed and bank material. [ABSTRACT FROM AUTHOR]

Water and mass exchange between rivers and lakes are key processes that maintain the health of the ecology of river-lake systems. Alteration to river-lake interactions have great impacts on water and mass balances. Naturally connected to the middle Yangtze River are the Poyang Lake and Dongting Lake, which are the largest and the second largest freshwater lakes in China. The operation of the Three Gorges Dam (TGD) in the upper Yangtze River was found to have substantial impacts on the middle Yangtze river-lake system. In the past decade, unusual seasonal dryness was evident in the two lakes. Considerable deviations in lake water quality and wetland ecosystem were also detected. In order to explore and distinguish the causal factors influencing the river-lake system, the Ministry of Sciences and Technology (China) launched a research project in 2012, the National Basic Research Program of China (973 Program) (2012CB417000). This article provides an overview of advances in this research, including the evolution of the river-lake interactions, the impacts of the TGD, and the influences on lake hydrology, water quality, and ecosystem. The 20 papers in this issue deliver part of the research outcomes of this project. [ABSTRACT FROM AUTHOR]

We analyse the change trends of the annual and seasonal runoff series of the hydrological station Batang on the headstream of the Yangtze River over the period 1960-2007. The relations between runoff series and precipitation and temperature conditions are investigated, and the influence of the refreezing process of meltwater of the glaciers on the Yangtze River flow is examined with the proposed accumulated temperature deficit (ATD) index. It is found that annual runoff at the Batang station is not stable during the period 1960-2007. From 1960 to 1980, there was a rather strong decrease of 14.4 m³ s-1 year-1 on average in spite of the statistically significant increase in air temperature and rather stable precipitation. It is argued that the annual rate of glacier runoff generation is possibly controlled by the ATD rather than by the direct air temperature. Seasonal analysis indicates that ATD might be of greater influence in autumn and winter in affecting runoff than in spring and summer. The research in this paper may be helpful in understanding how the hydro-climatic conditions affect runoff generation in the cold regions. [ABSTRACT FROM AUTHOR]

Due to the surface water in the upper reaches of Yangtze River in China containing large amounts of silt and algae, high content of microorganisms and suspended solids, the water in Yangtze River cannot be used for cooling a heat pump directly. In this paper, the possibility of using Yangtze River, which goes through Chongqing, a city in southwest China, as a heat source-sink was investigated. Water temperature and quality of the Yangtze River in the Chongqing area were analyzed and the performance of water source heat pump units in different sediment concentrations, turbidity and algae material conditions were tested experimentally, and the water quality standards, in particular surface water conditions, in the Yangtze River region that adapt to energy-efficient heat pumps were also proposed. The experimental results show that the coefficient of performance heat pump falls by 3.73% to the greatest extent, and the fouling resistance of cooling water in the heat exchanger increases up to 25.6% in different water conditions. When the sediment concentration and the turbidity in the river water are no more than 100 g/m³ and 50 NTU respectively, the performance of the heat pump is better, which can be used as a suitable river water quality standard for river water source heat pumps. [ABSTRACT FROM AUTHOR]

Inequality and polarization are terms usually used to describe the overall dispersion of income distribution and the phenomenon of a divided society with a disappearing middle class and increasing rich and poor populations. However, these terms have seldom been used in water sciences. In this paper, the concepts of inequality and polarization are employed to analyze the distribution of urban water use of different cities. Using for reference the conception of Gini coefficient, the EUWU (Equality of Urban Water Use) model is built to analyze the equality of urban water use. And, the PUWU (Polarization of Urban Water Use) model based on exponential functions, which can limit the index of polarization to the range (0, 1) effectively, is built to analyze the polarization of urban water use. Inequality and polarization of resident, industrial and commercial water use in 16 cities in the Yangtze River Delta, the fastest growing region of China, are evaluated using the EUWU model and PUWU model, respectively. The results show that inequality of residential, industrial and commercial water use has decreased by 6.5%, 11.2% and 8.4%, while the index of polarization has increased by 3.9%, 3.8% and 0.1% in Yangtze River Delta area from 2001 to 2006. [ABSTRACT FROM AUTHOR]