Little impact of the Three Gorges Dam on recent decadal lake decline across China's Yangtze Plain

Abstract

The ubiquitous lakes across China's Yangtze Plain (YP) are indispensable freshwater resources sustaining ecosystems and socioeconomics for nearly half a billion people. Our recent survey revealed a widespread net decline in the total YP lake inundation area during 2000–2011 (a cumulative decrease of ∼10%), yet its mechanism remained contentious. Here we uncover the impacts of climate variability and anthropogenic activities including (i) Yangtze flow and sediment alterations by the Three Gorges Dam (TGD) and (ii) human water consumption in agricultural, industrial, and domestic sectors throughout the downstream Yangtze Basin. Results suggest that climate variability is the dominant driver of this decadal lake decline, whereas studied human activities, despite varying seasonal impacts that peak in fall, contribute marginal fraction (∼10–20% or less) to the interannual lake area decrease. Given that the TGD impacts on the total YP lake area and its seasonal variation are both under ∼5%, we also dismiss the speculation that the TGD might be responsible for evident downstream climate change by altering lake surface extent and thus open water evaporation. Nevertheless, anthropogenic impacts exhibited a strengthening trend during the past decade. Although the TGD has reached its full‐capacity water regulation, the negative impacts of human water consumption and TGD‐induced net channel erosion, which are already comparable to that of TGD's flow regulation, may continue to grow as crucial anthropogenic factors to future YP lake conservation.

Characterizing Drought and Flood Events over the Yangtze River Basin Using the HUST-Grace2016 Solution and Ancillary Data

“…The water surpluses can be detected in 2010 and 2016, and water deficits can be observed in 2006, 2011 and 2013. The result is inconsistent with the recent findings over the YRB [2,3,42], indicating the flood and drought events in corresponding years. By the way, as shown in the top panel of Figure 2, the differences between the GLDAS and PCR-GLOBWB (SM) can be also seen in 2006 and 2011.…”

The impact of the Three Gorges Dam on summer streamflow in the Yangtze River Basin

“…These lake effects on streamflow occur in addition to the impacts imposed by the TGD (Wang et al, 2017). These lake effects on streamflow occur in addition to the impacts imposed by the TGD (Wang et al, 2017).…”

“…These lakes naturally attenuate the tributary flows, which impact flows to the main stem. These lake effects on streamflow occur in addition to the impacts imposed by the TGD (Wang et al, 2017). (2) The Yangtze River Basin consists of 21 subbasins (see Figure 1), whose runoff forms the main components of inflows at the four downstream hydrological stations.…”

“…Such events have raised concerns regarding the effectiveness of the dam in providing seasonal flow regulation. Past studies have focused on the TGD's impacts on downstream lakes, river levels and flows (Chen et al, 2016;Jiang, Ban, Wang, & Cai, 2014;Lai, Liang, Jiang, & Huang, 2014;Li, Lai, Dong, & Luo, 2016;Mei, Dai, van Gelder, & Gao, 2015;Wang, Sheng, Gleason, & Wada, 2013;Wang, Sheng, & Wada, 2017), however, the changes in flow regimes between naturalized flows and observed flows impacted by the dam and the underlying mechanism have been largely overlooked. Consequently, an analysis that compares estimated naturalized flows against flows regulated by the TGD in the period post impoundment is important for determining whether dam operations likely reduced or exacerbated low-flow or high-flow occurrences, and how the occurrence of these flow types have changed.…”

Assessing the effects of the Three Gorges Dam and upstream inflow change on the downstream flow regime during different operation periods of the dam

“…It has been revealed that the TGD displayed multiple behaviours altering downstream flow characteristics, such as decreasing and increasing discharge during the impoundment and release periods, respectively, and attenuating extreme flood peaks (Dai, Du, Li, Li, & Chen, 2008;Gao et al, 2012;Lai et al, 2014Lai et al, , 2017Mei et al, 2018;Wang, Wang, Lewis, Wu, & Huang, 2017). These variations in flow process due to the TGD were found to induce further hydrological alterations in water levels, droughts, interrelationships between the river and lakes, and even ecosystems of the downstream region (Guo et al, 2012;Li, Xiong, Dong, & Zhang, 2013;Mei, Dai, van Gelder, & Gao, 2015;Wang et al, 2013;Wang, Rhoads, & Wang, 2016;Wang, Sheng, & Wada, 2017;Zhang et al, 2012;Zhang, Ye, et al, 2014). In addition, the TGD was also proved to considerably decline the sediment load of the Yangtze River, resulting in alterations of the downstream river bed and delta (Chen, Wang, Finlayson, Chen, & Yin, 2010;Yang et al, 2006Yang et al, , 2007Zhao et al, 2015).…”