Variation in ecological flow regimes and their response to dams in the upper Yellow River basin

摘要

The upper Yellow River basin is located in the new Silk Road economic belt. Fundamental to the healthy development of the Yellow River ecosystem and the security of water resources in the economic belt are the hydrological regime change that drives river ecosystem processes, or called ecological flow regimes (EFR). When developing a sustainable and ecofriendly Silk Road economic belt, the evaluation of the alteration of the EFR and an attribute analysis should receive great attention because they can provide decision makers with more information on ecological implications for balancing environmental and human water needs. The objective of this paper is to investigate the EFR variation at the Lanzhou gauge as the control section of the upper Yellow River basin. First, the paper addresses the macroscale EFR using ecoflow metrics (ecodeficit and ecosurplus), i.e., the multi-year trend of the annual and seasonal changes in ecological flow. Second, it evaluates microscale variations in EFR via the Yellow River ecohydrological index system and compares them with macroscale changes in EFR to verify their consistency. Third, it analyzes the attributes of EFR variation and determines the impact of the construction and operation of reservoirs on the variation. Results show that macro-and microscale EFR at the Lanzhou gauge have significant changes before and after the construction of reservoirs in the upper Yellow River basin, reaching a high degree of alteration. Reservoir construction and operation have been the major reason for the alteration of EFR in the past few decades, and the cascade reservoir regulation has more significantly affected the changes in EFR than has a single reservoir, placing the downstream fluvial ecological system under serious risk. This change should arouse considerable concern, particularly in the development of the new Silk Road economic belt. In addition, ecoflow metrics used for reflecting the macroscale change in this study are highly correlated with microscale indicators of EFR that are accepted in the upper Yellow River basin. This result implies that ecoflow metrics can mirror most ecological information from these microscale indicators and are suitable for the evaluation of alterations in hydrological processes at annual and seasonal timescales.