Changes in water and sediment exchange between the Changjiang River and Poyang Lake under natural and anthropogenic conditions, China

Construction and operation of the Three Gorges Dam (TGD) has significantly altered the downstream hydrological regime along the Yangtze River, which has in turn affected the environment, biodiversity and morphological configuration, and human development. The ecological and environmental systems of the middle and lower Yangtze River have been affected adversely, with the ecosystems of Poyang Lake and its deltas being among the most damaged. Besides posing a potential threat to the survival of migrant birds and aquatic species, operation of the TGD has also affected the human population, particularly with respect to water and food security. Though the above mentioned effects have been studied in previous papers, a comprehensive discussion has never been conducted. This paper provides the first ever summary of the impacts of the TGD on the downstream reaches of the Yangtze River. The costs and benefits identified provide a constructive reference that can be used in decision-making for sustainable development of water resources in other nations, especially those in the developing world.

Section: Hydrological Regimementioning

confidence: 97%

Section: Hydrological Regimementioning

confidence: 99%

Impact of the Three Gorges Dam on the Hydrology and Ecology of the Yangtze River

Zhang

Dong

Gupta

et al. 2016

“…Outflows of the lake include water flowing into the Yangtze River at Hukou and direct evaporation from the lake surface. An extreme hydrologic regime of reverse flows from the Yangtze River to Poyang Lake can occur, as the Yangtze River heavily obstructs lake outflows, leading to the formation of a more prominent water stage in the Yangtze River than that of the lake surface from July to September when the Yangtze River undergoes its main flooding period [17,32]. The uneven distribution of catchment rainfall and impediment forces from the Yangtze River produces complex water stage fluctuations at Hukou.…”

Section: Study Areamentioning

confidence: 99%

Characteristics and Factors Influencing the Hysteresis of Water Area–Stage Curves for Poyang Lake

Huang

Peng

Liu

et al. 2017

Flood dynamics of large lake floodplain systems are typically complex. This paper analyses the characteristics and factors that influence the hysteresis of water area-stage curves for Poyang Lake, the largest freshwater lake in China characterized by complex geomorphology and upstream-downstream exchange conditions. For this purpose, a two-dimensional hydrodynamic model (EFDC) based on seven scenarios is established. The results indicate that the area-stage curve presents significant hysteretic characteristics due to different water surface gradients that emerge during the water-rising and water-falling periods. Counter-clockwise, clockwise, and splayed hysteresis directions observed at the northern, southern, and central hydrometric stations, respectively, are found in Poyang Lake for the first time. Upstream catchment inflows and Hukou stage reflecting the downstream condition are the main factors that influence hysteresis. The temporal fluctuation of catchment inflows and Hukou stage has a remarkably positive impact on hysteresis, namely, an increase in fluctuation brings about a larger hysteresis. The effects of magnitude change in the two factors on hysteresis are opposing. Catchment inflows are positively related, while the decline of the Hukou stage will produce a more pronounced hysteresis. The outcomes of this study will benefit the water management of Poyang Lake and other similar large lakes.

“…Poyang Lake is geometrically complex with tortuous shorelines and incised bottom morphology, which has been shaped by a combination of lacustrine and riverine morphological processes [40]. Based on historical measures of the lake surface during periods with high water levels in combination with recognition of the extensive levee system (in order to separate artificial wetlands from nature wetlands), a study area covering 3124 km 2 was determined using GIS (Geographic Information System) techniques.…”

Section: Study Areamentioning

confidence: 99%

Spatial–Temporal Dynamics of Wetland Vegetation Related to Water Level Fluctuations in Poyang Lake, China

Tan

Jiang

2016

Hydrological properties are driving forces of wetland systems. The influence of water level fluctuations on vegetation distribution is of growing interest as wetlands are increasingly disturbed by climate change and intensive human activity. Based on time series MODIS (Moderate Resolution Imaging Spectroradiometer) imagery from 2000 to 2012, we investigated the spatial-temporal dynamics of wetland vegetation in Poyang Lake using a combined Sen's slope and Mann-Kendall (MK) test approach, and explored their correlations with water level fluctuations in different hydrological periods. The results showed that more than 34% of wetlands at lower elevations of Poyang Lake had experienced an increasing trend in the enhanced vegetation index (EVI), whereas EVI in about 11% of the wetlands at higher elevations decreased significantly. Responses of grassland area extracted from MODIS EVI were found to be more sensitive to water level fluctuations in the southern lakes. The change rate of grassland area decreased with the rising water level during the rising period, but increased with the rising water level during the retreating period. Correlations between grassland area and water level were much weaker in the dry period. In addition, we found fluctuations of the main water body had negligible effect on grassland area since the water level at Xingzi station was below 14 m. These results provide new insights for predicting future changes of wetland vegetation influenced by the ongoing threats from climate change and human activity, and form a foundation for ecosystem management of Poyang Lake.