The impact of Three Gorges Dam on the downstream eco‐hydrological environment and vegetation distribution of East Dongting Lake

Abstract

The ecological and environmental consequences of large dam projects have received increasing attention in the recent decades. On the basis of daily water‐level data, six periods of TM/ETM+ data and a digital elevation model, the eco‐hydrological environments and vegetation area of East Dongting Lake, were compared for the years 1995–2011, spanning periods before and after the implementation of the Three Gorges Dam (TGD) in 2003. Vegetation area (including three types: forestry, reed and grass) continuously expanded, and the minimum elevation of vegetation‐covered area (VCA) gradually decreased by 0·88 m from 1995 to 2011. Following the implementation of the TGD, the rates of both vegetation expansion (12·3 vs 14·1 km2 year−1) and the lowering of minimum elevation of VCA (3·1 vs 7·9 cm year−1) increased rapidly. Monthly water level decreased considerably from July to November, and annual submergence duration at elevations of 22–26 and 30 m was considerably decreased after the TGD was implemented. The average maximum submergence duration of VCA was 231 days. Almost equal linear equations describing elevation change from 1995 to 2011 indicated that the minimum elevation of VCA identified via analysis of TM/ETM+ images can be represented by the maximum submergence duration evaluated via daily water level. These data indicate that vegetation colonized the non‐vegetation area (including mud beach or water body) more quickly after the implementation of the TGD, due to the drastic changes in eco‐hydrological environments such as the decreasing water level and the minimum elevation of VCA. The present methodology might allow faster and more reliable assessment of inundation related landscape impacts on a basin scale and thereby contribute to biodiversity monitoring and policy assessment. Copyright © 2014 John Wiley & Sons, Ltd.

Changes in carbon and nitrogen cycling in a floodplain lake over recent decades linked to littoral expansion, declining riverine influx, and eutrophication

“…Dongting Lake is a hydrologically open lake (Figure ), with a mean water depth of 6.4 m and a drainage area of 263,000 km 2 . The lake and its beach wetlands provide valuable habitats for 1,428 plant, 114 fish, and 217 bird species (Xie, Tang, Chen, Li, & Deng, ). Due to its high biodiversity, this region has been recognized as one of the Global 200 conservation priority ecoregions (Olson & Dinerstein, ).…”

Dramatic variations in emergent wetland area in China's largest freshwater lake, Poyang Lake

“…The two lakes have suffered significant hydrological variations since the construction of the TGD ( Chang et al, 2010;Mei et al, 2015 ). The wintertime growth rate of EWA in the East Dongting Lake has increased from 12.3 km 2 /year to 14.1 km 2 /year after the construction of the TGD, while the minimum EWA elevation has been reducing at a rate of 7.9 cm/year with respect to a decreasing rate of 3.1 cm/year for the period 1995-2003 ( Xie et al, 2015 ). In the same period, Poyang Lake experienced similar hydrological trends.…”

The influence of natural factors on the spatio-temporal distribution of Oncomelania hupensis

“…However, in this study, the space-time differences in the effect that NDVI had on snails were not caused by spatio-temporal variability itself. Based on this situation, we should consider the influence of not only other natural factors but also changes in the local environment related to snail survival caused by human activities (Liang et al, 2012;Xie et al, 2014). For example, the impoundment of the Three Gorges project and the South to North Water Diversion Project have changed the wetland pattern of Dongting Lake in recent years, thereby affecting the distributions of snails there (Hu et al, 2015a,b;Liu et al, 2016).…”