Effect of global climate change on the sustainability of cold-water fish habitat in the alpine region: A case study on the Gymnocypris eckloni in the source region of the Yellow River.

Climate change at the global scale affects the watershed's hydrology and the river's hydrodynamic, water temperature (WT), and habitat conditions of organisms. This article proposes a quantitative assessment methodology framework for analyzing the impact of GCC on the cold-water fish habitat. This framework integrated GCC, downscaling, hydrological, hydrodynamic, water temperature, and habitat models and was applied to the source region of the Yellow River (SRYR), where there are Gymnocypris eckloni (G. eckloni) resource reduction problems. In this study, we developed a high-precision, loosely integrated hydrological, hydrodynamic, WT coupling model for SWAT-MIKE21 in the SRYR. The optimal latitude and longitude range (6° × 6°) covering the SRYR was established for downscaling, and future meteorological data under three GCC models was obtained. The main results present the discharge of spawning, and juvenile G. eckloni indicates an increasing trend from the radiation forcing low to high and from the near now to the future term. The WT increased (decreased) in April and June (May), with a maximum increase/decrease of 3.1°C (SSP370 in 2100)/1.4°C (SSP585 in 2050). The weighted useable area (WUA) demonstrated a trend of severe fluctuations in May, June, and October, and other months are equal to the base year. Total WUA (TWUA) displayed an increasing trend, with the maximum increase in spawning and juvenile period being 134.46% and 270.89%, respectively. Ultimately, the rise in confluence discharge and WT caused by GCC in the SRYR benefits spawning and juvenile G. eckloni. The results have guiding significance for the development of long-term and adaptive protection and restoration measures for G. eckloni, and provide a plan for predicting the impact of climate change on other organisms in river ecosystems in high-altitude cold regions.

Coordination analysis of flood-sediment transportation, eco-environment, and socio-economy coupling in the governance of the Yellow River Basin system.

The watershed system has a complex game relationship between the benign operation and coordinated development of various elements of flood-sediment transportation, eco-environment, and socio-economy (FES). With the increasing breadth, depth, and intensity of human activities in watersheds, it is urgent to coordinate the FES. The relationship of water-sediment in the Yellow River Basin (YRB) is complex, with a prominent contradiction in water supply and a fragile ecosystem. This research tries to build a comprehensive evaluation model for FES and explore the complex interaction between FES in the YRB from 2000 to 2020. The results demonstrated that (1) the comprehensive flood-sediment transportation index (CFTI) and comprehensive eco-environment index (CEI) presented fluctuating growth. In contrast, the comprehensive socio-economy index (CSI) revealed a linear growth trend. The CFTI of Sanmenxia, CEI of Toudaokuan, and CSI of Ningxia had the highest growth rates, with 36.03%, 6.48%, and 107.5%, respectively. (2) FES's positive and negative effects were alternating, with heterogeneity in both time and space. (3) The coupling coordination degree (CCD) in the YRB indicated an increasing trend, ranging from 0.53 to 0.87, from reluctantly coordinated development to good coordinated development. The lagging subsystem was CFTI (2000-2001 and 2008-2020) and CSI (2002-2007), and the CEI was not lagging. (4) Exploratory Spatial Data Analysis (ESDA) demonstrated significant differences in the CCD of the YRB, and areas with similar CCD within the basin tend to be centrally distributed in space. At the same time, there was negative spatial autocorrelation in coordination. The results provide a scientific theoretical and methodological framework for strategic research on the YRB system's governance, protection, and management.