A framework to assess the cumulative impacts of dams on hydrological regime: A case study of the Yangtze River

Abstract

Comparisons of flow time series between preimpact and postimpact periods have been widely used to determine hydrological alterations caused by reservoir operation. However, preimpact and postimpact periods might also be characterized by different climatological properties, a problem that has not been well addressed. In this study, we propose a framework to assess the cumulative impact of dams on hydrological regime over time. The impacts of the Three Gorges Dam (TGD) on the flow regime of the Yangtze River were investigated using this framework. We reconstructed the unregulated flow series to compare with the regulated flow series during the same period (2010 to 2015). Eco-surplus and eco-deficit and the Indicators of Hydrologic Alteration (IHA) parameters were used to examine hydrological regime change. Among 32 IHA parameters, Wilcoxon signed-rank test and principal component analysis identified the October median flow, 1-and 3-day maximum flows, 1-day minimum flow, and rise rate as representative indicators of hydrological alterations. Eco-surplus and eco-deficit showed that the reservoir also changed the seasonal regime of the flows by reducing autumn flow and increasing winter flow. Changes in annual extreme flows and October flows lead to negative ecological implications downstream of the TGD. Ecological considerations should be taken into account during operation of the TGD in order to mitigate the negative effects on the fluvial ecosystem in the middle reach of Yangtze River. The framework proposed here could be a robust method to assess the cumulative impacts of reservoir operation over time.

Long-Term Trends and Seasonality Detection of the Observed Flow in Yangtze River Using Mann-Kendall and Sen’s Innovative Trend Method

“…The Yangtze River is one of the longest rivers around the world, which collects water from several catchments [43]. The flow is monitored through several gauges along the river [44]. The Yangtze River covers one-fifth of the entire country with a region of about 1.8 million km 2 .…”

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

“…The changes of the downstream flow process appear to be the most direct and apparent results of the regulation of the TGD and have been widely studied. 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).…”

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

“…The eco-flow metrics have been successfully applied for analyzing flow regime changes in different regions [20][21][22]. Gao et al [23] and Wang et al [24] found that the eco-flow metrics can describe changes in the hydrological parameters of groups 1 and 2 of the IHA metrics (i.e., the magnitude of monthly runoff and the magnitude of extreme runoff, respectively). This finding provides an opportunity to reduce the number of metric parameters used for the evaluation of flow regime changes using the eco-flow metrics.…”