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Publication Date
12 February 2016

The Fan of Influence of Streams and Channel Feedbacks to Simulated Land Surface Water and Carbon Dynamics



Large-scale land models assume unidirectional land-to-river hydrological interactions, without considering feedbacks between channels and land. Using a tested, physically-based model with explicit multi-way interactions between overland, channel, wetland, and groundwater flows, we assessed how the representation and properties of channels influence simulated land surface hydrologic, biogeochemical, and ecosystem dynamics. A zone near the channels where various fluxes and states are significantly influenced by the channels, referred to as the fan of influence (FoI) of channels, has been identified. We elucidated two mechanisms inducing the model-derived FoI: the baseflow mechanism, in which incised, gaining streams lower the water table and induce more baseflow, and the relatively more efficient conveyance of the channel network compared to overland flow. We systematically varied drainage density and grid resolution to quantify the size of theFoI, which is found to span a large fraction of the watershed (25%∼50%) for hydrologic variables including depth to water table and recharge, etc. The FoI is more pronounced with low-resolution simulations but remains noticeable in hyper-resolution (25 m) subbasin simulations. The FoI and the channel influence on basin-average fluxes are also similar in simulations with alternative parameter sets. We found that high order, entrenched streams cause larger FoI. In addition, removing the simulated channels has disproportionally large influence on modeled wetland areas and inundation duration, which has implications for coupled biogeochemical or ecological modeling. Our results suggest that explicit channel representation provides important feedbacks to land surface dynamics which should be considered in meso- or large-scale simulations. Since grid refinement incurs prohibitive computational cost, sub-grid channel parameterization has advantages in efficiency over grid-based representations that do not distinguish between overland flow and channel flow. This article is protected by copyright. All rights reserved.

“The Fan Of Influence Of Streams And Channel Feedbacks To Simulated Land Surface Water And Carbon Dynamics”. 2016. Water Resources Research. doi:10.1002/2015WR018086.
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