Exceptional increases in fluvial sediment fluxes in a warmer and wetter High Mountain Asia

Abstract

Muddied waters The climate of High Mountain Asia is becoming warmer and wetter. Li et al . present data showing that rivers originating in this region have experienced large increases in runoff and sediment fluxes over the past six decades, most dramatically since the mid-1990s. The authors project that sediment flux from those rivers could more than double by 2050 in the case of extreme climate change, with potentially serious impacts on the region’s hydropower capacity, food security, and environment. —HJS

Rapid changes to global river suspended sediment flux by humans

“…We are unable to detect whether climate change and attendant changes to the hydrologic cycle have demonstrably contributed to changes in sediment supply. Some watersheds have experienced increased precipitation ( 16 ) or temperature-related erosion ( 3 ) during this period (fig. S6).…”

“…Sediment fluxes from this continent have increased, in both relative and absolute terms, as declines have occurred in the Northern Hemisphere. South American rivers represent 52 ± 2.6% of the global total and, despite increases in river headwater sediment fluxes in Asia ( 3 ), are now the leading exporters of sediment to the oceans.…”

“…River basins globally are experiencing increasing threats to their key roles in physical and ecological processes, including increased erosion from land use changes, sediment trapping by dam building, and the cascading hydrological and sedimentological effects of climate change ( 1 ). In many basins, the past and ongoing relative impacts of each of these changes remain unknown because of insufficient monitoring, and future projections are hindered by nonstationary watershed behavior, including changes without recent or well-monitored precedents ( 2 , 3 ). Given the divergent impacts of these different stressors—with land-use change dominantly increasing sediment flux, sediment trapping by dams dominantly decreasing sediment flux, and the effect of climate change on sediment flux uncertain—the temporal and global spatial variations in current and future net impacts are poorly constrained.…”

Constraining Dynamic Sediment‐Discharge Relationships in Cold Environments: The Sediment‐Availability‐Transport (SAT) Model

“…Ongoing climate change has already significantly impacted suspended sediment loads in cold environments by regulating the sediment generation, delivery, and deposition processes (Bendixen et al., 2017; Jaeger & Koppes, 2016; Knight & Harrison, 2012; Li et al., 2021b). Substantial increases in sediment fluxes have been reported for many cold basins due to the accelerating melt of cryosphere in a warming climate (Delaney & Adhikari, 2020; Lewkowicz & Way, 2019; Li, Li, Zhou, & Lu, 2020; Overeem et al., 2017).…”

Response of runoff components to climate change in the source‐region of the Yellow River on the Tibetan plateau

“…The source‐region of the Yellow River (SYR) on the Tibetan Plateau is deemed as the “water tower” of the Yellow River (Immerzeel et al, 2010; Yuan et al, 2018) because it contributes 55%–70% of the annual runoff in the entire Yellow River with a drainage area fraction of only 16% (121 790 km 2 ) (Table S1) (Zhou & Huang, 2012). The recent amplified climate change on the Tibetan Plateau has accelerated glacier‐snow‐permafrost degradation and impacted the hydrological processes in many headwater regions (Immerzeel et al, 2020; Li et al, 2020; Li et al, 2021; Wang et al, 2021), triggering significant social and economic uncertainties to the downstream regions (Duan et al, 2020; Pritchard, 2019; Zheng et al, 2009). Thus, understanding how streamflow in SYR, particularly various runoff components (e.g., glacier‐melt flow, snowmelt flow, rainfall flow, and baseflow), respond to climate change has important implications for future water resource management in the entire Yellow River.…”