scholarly journals Analyzing Changes in the Flow Regime of the Yangtze River Using the Eco-Flow Metrics and IHA Metrics

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1552 ◽  
Author(s):  
Bing Gao ◽  
Jie Li ◽  
Xiaoshu Wang
Keyword(s):  
Flow Regime ◽  
Reservoir Operation ◽  
Yangtze River ◽  
Main Channel ◽  
Climate Variation ◽  
Low Flow ◽  
Distributed Hydrological Model ◽  
The Yangtze River ◽  
Regime Changes ◽  
Precipitation Decrease

Changes in the flow regime of the Yangtze River were investigated using an efficient framework that combined the eco-flow metrics (ecosurplus and ecodeficit) and Indicators of Hydrologic Alteration (IHA) metrics. A distributed hydrological model was used to simulate the natural flow regime and quantitatively separate the impacts of reservoir operation and climate variation on flow regime changes. The results showed that the flow regime changed significantly between the pre-dam and post-dam periods in the main channel and major tributaries. Autumn streamflow significantly decreased in the main channel and in the tributaries of the upper Yangtze River, as a result of a precipitation decrease and reservoir water storage. The release of water from reservoirs to support flood regulation resulted in a significant increase in winter streamflow in the main channel and in the Minjiang, Wujiang, and Hanjiang tributaries. Reservoir operation and climate variation caused a significant reduction in low flow pulse duration in the middle reach of the Yangtze River. Reservoir operation also led to an increase in the frequency of low flow pulses, an increase in the frequency of flow variation and a decrease in the rate of rising flow in most of the tributaries. An earlier annual minimum flow date was detected in the middle and lower reaches of the Yangtze River due to reservoir operation. This study provides a methodology that can be implemented to assess flow regime changes caused by dam construction in other large catchments.

Impact of the Three Gorges reservoir operation on downstream ecological water requirements

2012 ◽  
Vol 43 (1-2) ◽  
pp. 48-53 ◽  
Author(s):  
Qiongfang Li ◽  
Meixiu Yu ◽  
Jianhua Zhao ◽  
Tao Cai ◽  
Guobin Lu ◽  
...  
Keyword(s):  
Flow Regime ◽  
Reservoir Operation ◽  
Yangtze River ◽  
Three Gorges Reservoir ◽  
Three Gorges ◽  
The Yangtze River ◽  
Water Requirements ◽  
The Three Gorges Reservoir ◽  
The Three Gorges ◽  
Ecological Water Requirements

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.

scholarly journals Assessment of the Multi-Objective Reservoir Operation for Maintaining the Turbidity Maximum Zone in the Yangtze River Estuary

2018 ◽  
Vol 15 (10) ◽  
pp. 2118 ◽  
Author(s):  
Yang Yu ◽  
Peifang Wang ◽  
Chao Wang ◽  
Xun Wang ◽  
Bin Hu
Keyword(s):  
Reservoir Operation ◽  
Yangtze River ◽  
Environmental Flows ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
The Yangtze River ◽  
Operation Model ◽  
Hydropower Generation ◽  
Quantitative Correlation ◽  
The Yangtze River Estuary

The construction of multifunction reservoirs is important for flood control, agriculture irrigation, navigation, and hydropower generation, but dam construction will inevitably affect the downstream flow and sediment regimes, which can cause some environmental and ecological consequences. Therefore, this paper aims to propose a framework for assessing the multiobjective reservoir operation model based on environmental flows for sustaining the suspended sediment concentration (SSC) requirements in the turbidity maximum zone (TMZ). The Yangtze River Estuary was used as a case study. Through using an analytical model, a quantitative correlation between SSC and water flow rate was established. Then, the quantitative correlation and the SSC requirements were applied to determine the environmental flows for the estuarine TMZ. Subsequently, a multiobjective reservoir operation model was developed for the Three Gorges Reservoir (TGR), and an improved nondominated sorting genetic algorithm III based on elimination operator was applied to the model. An uncertainty analysis and a comparative analysis were used to assess the model’s performance. The results showed that the proposed multiobjective reservoir operation model can reduce ecological deficiency under wet, normal, and dry years by 33.65%, 35.95%, and 20.98%, with the corresponding hydropower generation output lost by 3.37%, 3.88%, and 2.95%, respectively. Finally, we discussed ecological satiety rates under optimized and practical operation of the TGR in wet, normal, and dry years. It indicated that the multiobjective-optimized runoff performs better at maintaining the TMZ in the Yangtze River Estuary than practical runoff. More importantly, the results can offer guidance for the management of the TGR to improve the comprehensive development and protection of the estuarine ecological environment.

scholarly journals Variation of the Water Level in the Yangtze River in Response to Natural and Anthropogenic Changes

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2594 ◽  
Author(s):  
Jinxin Liu ◽  
Jinyun Deng ◽  
Yuanfang Chai ◽  
Yunping Yang ◽  
Boyuan Zhu ◽  
...  
Keyword(s):  
Water Level ◽  
Yangtze River ◽  
Dry Season ◽  
Climate Variation ◽  
Dominant Factor ◽  
The Yangtze River ◽  
Flood Season ◽  
Dam Operation ◽  
Adjustment Mechanisms ◽  
Measured Water

The water level in the Yangtze River has significantly changed due to the effects of varied precipitation and dam operations, which have exerted significant effects on irrigation, navigation, and ecosystems. Based on the measured data and the proposed calculation method, we analyzed the adjustment mechanisms of the seasonal water level in the whole Yangtze River. The results were as follows. During the dry season, the rising precipitation and dam operation both increased the water level in the upper reaches and in the reaches from the Jianli to Datong stations during 1981–2014. Moreover, dam operations were the dominant factor (except at Datong station). In the reaches from the Yichang to Shashi stations, dam operations are the reason for the reduction of the measured water level in the dry season, while the rising precipitation had an opposite influence. During the flood season, dam operations helped to reduce the water level from the upper reaches to the estuary during 1981–2014, while climate variation stresses adversely affected the entire river basin. In the reaches between the Luoshan and Jianli stations, climate variation is the dominant factor for the increased water level during the flood season, while dam operation is the reason for the reduced water level at the other six hydrological stations.

scholarly journals Long-Term Impacts of Reservoir Operation on the Spatiotemporal Variation in Nitrogen Forms in the Post-Three Gorges Dam Period (2004–2016)

2021 ◽  
Author(s):  
Bei Nie ◽  
Yuhong Zeng ◽  
Lanhua Niu ◽  
Xiaofeng Zhang
Keyword(s):  
Water Quality ◽  
Reservoir Operation ◽  
Yangtze River ◽  
Ammonia Nitrogen ◽  
Three Gorges ◽  
The Yangtze River ◽  
Engineering Construction ◽  
Nitrogen Concentrations ◽  
Essential Nutrient

Abstract Nitrogen (N) is an essential nutrient limiting life, and its biochemical cycling and distribution in rivers have been markedly affected by river engineering construction and operation. Here, we comprehensively analyzed the spatiotemporal variations and driving environmental factors of N distributions based on the long-term observations (from 2004 to 2016) of seven stations in the Three Gorges Reservoir (TGR). In the study period, the overall water quality status of the river reach improved, whereas N pollution was severe and tended to be aggravated after the TGR impoundment. The anti-seasonal reservoir operation strongly affected the variations in N forms. The total nitrogen (TN) concentration in the mainstream of the Yangtze River continuously increased, although it was still lower than that in the incoming tributaries (Wu and Jialing rivers). Further analysis showed that this increase occurred probably because of external inputs, including the upstream (76%), non-point (22%), and point source pollution inputs (2%). Besides, different N forms showed significant seasonal variations; among them, the TN and nitrate nitrogen concentrations were the lowest in the impoundment season (October–February), and the ammonia nitrogen concentrations were the highest in the sluicing season (March–May). These parameters varied likely because of internal N transformation. Redundancy analysis revealed that the water level regulated by the anti-seasonal operation was the largest contributor. Our findings could provide a basis for managing and predicting the water quality in the Yangtze River.

Changing low flow seasonality in Central European headwaters

2021 ◽  
Author(s):  
Vojtech Vlach ◽  
Ondrej Ledvinka ◽  
Milada Matouskova
Keyword(s):  
Flow Regime ◽  
R Package ◽  
Hydrological Drought ◽  
Low Flow ◽  
Significant Shift ◽  
Regime Changes ◽  
Seasonality Index ◽  
Long Term Trends ◽  
Summer Minimum ◽  
Hydrological Droughts

<p>In the environment of the changing climate in Central Europe, the seasonality and magnitude of low flow events and hydrological droughts are projected to change in the near future. Ongoing increases in the air temperature, rates of evaporation and decreasing snow cover will significantly affect the summer deficit volumes even in the rivers of humid montane and highland areas in mid-latitudes. However, what if the significant changes have already been happening during the last decades? Therefore, this research is focused on analysis of the variability and seasonality of low flow events and hydrological drought events in fifteen near-natural catchments along the Czech–German and Czech–Polish national borders. To quantify the low flow regime changes of the study regions in the last 52 years (1968–2019), we applied tools from the R package lfstat. The 30-year moving averages of seasonality ratio (SR) and the seasonality index (SI) were derived to address the degree of change in each catchment. Moreover, the 7-day and 30-day mean summer minimum discharges were computed, as well as the streamflow deficit volumes for every episode of hydrological drought. The results showed a continual increase in the proportion of summer low flow and drought events during the study period along with a significant shift in the average date of low flow occurrence towards the beginning of the year. The most marked shifts in low flow seasonality were found mainly in catchments with the average altitude 800–1000 m a. s. l. Conversely, the low flow regime in catchments above 1000 m a. s. l. and also in the catchments below 800 m a. s. l. remained nearly stable throughout the 1968–2019 period. Moreover, the analysis of 7- and 30-day mean summer minimum discharges indicated a much-diversified pattern in the behavior of long-term trends than it was expected.</p>

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