Has the Three‐Gorges Dam made the Poyang Lake wetlands wetter and drier?

Abstract

The Three‐Georges Dam holds many records in the history of engineering. While the dam has produced benefits in terms of flood control, hydropower generation and increased navigation capacity of the Yangtze River, serious questions have been raised concerning its impact on both upstream and downstream ecosystems. It has been suggested that the dam operation intensifies the extremes of wet and dry conditions in the downstream Poyang Lake, and affects adversely important local wetlands. A floodgate has been proposed to maintain the lake water level by controlling the flow between the Poyang Lake and Yangtze River. Using extensive hydrological data and generalized linear statistical models, we demonstrated that the dam operation induces major changes in the downstream river discharge near the dam, including an average “water loss”. The analysis also revealed considerable effects on the Poyang Lake water level, particularly a reduced level over the dry period from late summer to autumn. However, the dam impact needs to be further assessed based on long‐term monitoring of the lake ecosystem, covering a wide range of parameters related to hydrological and hydraulic characteristics of the lake, water quality, geomorphological characteristics, aquatic biota and their habitat, wetland vegetation and associated fauna.

Modelling Tools to Analyze and Assess the Ecological Impact of Hydropower Dams

“…However, due to the models' complexity, the model is able to assess various outcomes as there are a variety of metrics that help assess a particular course of action. Conversely, Zhang et al [132] predicted the water flow using only the rainfall data and included a cyclic function to take into account the evaporation effect. They developed a very simple model that oversimplifies the numerous hydrological processes.…”

Plant-mediated methane and nitrous oxide fluxes from a carex meadow in Poyang Lake during drawdown periods

“…Carex meadows experience two growing seasons that occur in the spring and in autumn after the summer flooding (Hu et al 2010). In recent years, climate change and the operation of the Three Gorges Dam (since 2003) have largely altered the hydrological regime of Poyang Lake, resulting in a reduction of the summer flooding duration and extension of drawdown periods (Zhang et al 2012). Quantifying GHG fluxes from Carex meadows during drawdown periods will help to advance the understanding of biogeochemical processes in response to ongoing climate warming and hydrological change in this large subtropical lake.…”

Hydroclimatological influences on recently increased droughts in China's largest freshwater lake

“…A number of studies have documented this decline in Poyang Lake and its influencing factors (Guo et al, 2012;Zhang et al, 2012;Liu et al, 2013;Lai et al, 2014a;Zhang et al, 2014). Feng et al (2012) used satellite images with a 250 m spatial resolution and reported that the lake size had a decreasing trend between 2000 and 2010.…”

“…Although the region historically experiences significant floods (Shankman and Liang, 2003;Shankman et al, 2006), severe lake droughts have occurred frequently in the past decade, resulting in tremendous hydrological, biological, ecological and economic consequences Environment News Service, 2012;Wu and Liu, 2014). Because the lake is the primary part of the well-known Poyang Lake wetland and the lake region serves as an important food base for China, the frequently occurring lake droughts have also received increasing international attention (Jiao, 2009;Finlayson et al, 2010;Liu et al, 2011;Environment News Service, 2012;The Ramsar Convention, 2012;Zhang et al, 2012Zhang et al, , 2014.…”

“…The modification was largely attributable to the operation of the Three Gorges Dam (TGD), established upstream of the Yangtze River in 2003. Water impoundments of the TGD incurred water level drops with an average estimate of 2 m at the outlet of Poyang Lake in mid-September to November for the period 2003-2008(Guo et al, 2012Zhang et al, 2012). Alternatively, Lai et al (2013) developed a hydrodynamic model for the middle Yangtze River region (CHAM-Yangtze), in which they coupled both Poyang Lake and the Yangtze River to account for the lake-river interactions explicitly.…”