Abstract

Suspended sediment plays a vital role in the regional and global cycling of carbon and nutrients by carrying carbon and nutrients from headwaters into lowland rivers and the oceans. Sediment transport through river systems is often fundamentally modified by human activities like reservoir management. However, a physically based representation of sediment transport is still missing in most existing earth system models (ESMs), which are essential tools for modeling and predicting earth system changes. Here, we introduce a multi-process river sediment module for ESMs, which includes: 1) hillslope soil erosion and sediment discharge into streams; 2) sediment transport processes through river networks; 3) reservoir operation based on the inflows from upstream areas and water demand from downstream areas; and 4) sediment trapping by reservoirs. All model parameters are estimated a priori without calibration. We apply this new sediment modeling framework to the contiguous United States and validate it against historical observations of monthly streamflow and sediment discharges at 35 river gauges. The model reasonably well captures the long-term balance and seasonal variations of suspended sediment in large river systems. Furthermore, our model results show that suspended sediment discharge in managed rivers is affected more by reservoirs' direct trapping of sediment particles than by their flow regulation. This new sediment module enables future modeling of the transportation and transformation of carbon and nutrients carried by the fine sediment along the river-ocean continuum to close the global carbon and nutrients cycles.

Highlights

  • Increasing evidence showed that suspended sediment transport 60 plays a vital role in regional and global carbon and nutrient cycling (Berhe et al, 2018; Lal, 2003, 2004; Ludwig & Probst, 1996; Maavara et al, 2020; Van Oost et al, 2007) by carrying carbon and nutrients from soil storage pools into rivers and eventually oceans or lakes

  • Most Earth System Models (ESMs) have been developed with a conventional assumption that the lateral carbon fluxes through the land-riverocean continuum are not significant, compared to the carbon dynamics within the larger carbon pool in the atmosphere, land, 70 and ocean or to the vertical carbon fluxes between the atmosphere and the underlying land and ocean

  • Model for Scale Adaptive River Transport (MOSART) explicitly incorporates the processes of overland flow routing across hillslopes, channel routing through tributaries and main channel networks, and water management such as reservoir regulation and surface water withdrawal, providing a solid physical basis to represent suspended sediment dynamics in both natural and managed rivers

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Summary

25 Abstract

Suspended sediment plays a vital role in the regional and global cycling of carbon and nutrients by carrying carbon and nutrients from headwaters into lowland rivers and the oceans. All model parameters are estimated a priori without calibration We apply this new sediment modeling framework to the contiguous United States and validate it against historical observations of monthly streamflow and sediment discharges at 35 river gauges. Our model results show that suspended sediment discharge in managed rivers is affected more by reservoirs' direct trapping of sediment particles than by their flow regulation. This new sediment module enables future modeling of the transportation and transformation of carbon and nutrients carried by the fine sediment along the riverocean continuum to close the global carbon and nutrients cycles

Introduction
Modeling Framework
MOSART-water
MOSART-sediment
Study Area
Numerical Experiments
Model Validation
Model Structure
Impacts of reservoirs on suspended sediment discharge to the coasts
675 References
Methods
Full Text
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