Abstract
Many studies have found that damming a river can change downstream hydrology, sediment transport, channel morphology, and fish habitat. However, little is known about river dam effects on downstream riparian wetland dynamics and their quantitative relationship with hydrological alterations. In this study, hydrological time series and wetland distribution data spanning nearly 40 years (1978–2016) before and after the construction of a large dam in 2005 across the Nenjiang River in Northeast China were used to reveal the impact of dam on the downstream discharge regime and wetland degradation. Hydro-statistical and stepwise multiple regression analyses were performed to quantify the relationship of riparian wetland area with a metrics of 33 hydrological indicators. Dam construction caused decline in peak discharge, flood frequency, and magnitude. Moreover, 150 km riparian wetlands along the downstream of the dam was largely reduced. The count and duration of high flow pulses, 1-day maximum, and date of maximum discharge changed significantly after the dam construction. The hydrological changes have made a significant contribution to the 44% reduction in riparian wetlands following the dam construction. Our results indicated that hydrological alterations caused by dam regulation led to the area reduction of downstream riparian wetlands. The findings provide relevant information for developing best dam operation practices to protect and restore downstream wetland ecosystems.
Highlights
The construction by damming rivers has considerably altered downstream hydrologic regimes around the world [1,2,3,4,5]
This study focuses on how hydrologic changes following a dam construction can affect downstream riparian wetlands
We investigated hydrologic alteration and riparian wetland changes after dam study, we have only investigated the impact of hydrological conditions on wetland degradation
Summary
The construction by damming rivers has considerably altered downstream hydrologic regimes around the world [1,2,3,4,5]. Considering that 85% of the total rivers were controlled and fragmented by dams [6], many downstream hydrologic effects of dams are noticeable and direct. Dams are built for regulating discharge to ensure water supply [8]. On the other hand, damming rivers can help flood control, which can reduce intensity of downstream inundation [9] and make the channel occasionally or enduringly dry or at least significantly reduce discharge, which can alter the floodplain and river channel [10].
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