Development of a comprehensive framework for assessing the impacts of climate change and dam construction on flow regimes

The undeniable fact of climate change and dam construction alters the hydrological systems and threatens aquatic ecosystems of rivers around the world. Quantifying the impact of climate change and dam construction on flow regime is essential for water resources management and environmental protection. However, previous studies have rarely separated the effects of two factors on flow regimes, and the individual impact of each remains insufficient to date. Moreover, the existing methods have not fully captured the characteristics and temporal changes of flow regimes. In this study, we propose a new framework that integrates a streamflow reconstruction technique, indicators of hydrologic alteration (IHA), indicators of intra-annual flow variations, a revised range of variability approach to assessing the climate change and dam-induced impacts on the flow regime. The Upper Yellow River Basin (UYRB) was selected as the study area. The results show that climate change significantly reduces the monthly flow, extreme water conditions and the intra-annual indicators, and advances the Julian date of annual maximum flow. Dam construction delays the Julian date of annual maximum flow that opposes climate change impact, reduces the monthly flow in the flood season and the annual maximum flow, but increases the monthly flow in the dry season and annual minimum flow. Changes in flow regimes in the UYRB are found to be mainly due to climate change albeit there exists a cascade of dams. Based on the range of variability approach (RVA), fifteen of forty indicators are moderately changed. While the number increases to thirty-seven when considering the temporal order alteration of flow regime. The case study demonstrates that the developed framework can serve as a useful tool to evaluate the impact of climate change and dam construction on flow regimes.