Analysis of the Impact of Simulated Channel Density on Hydrologic Responses with a Physically-based Hydrologic Model (PAWS+CLM)

Monday, May 12, 2014 - 07:00
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Channel network is an integral and important component of the hydrologic cycle that exerts influences on not only in-channel but also upland processes. The selection of represented channels in channel-explicit models has always been arbitrary and scale-dependent. There was no systematic study on the effect of channel density (CD) on hydrologic dynamics, especially in the upland. In this study we systematically varied CD from a high-CD, high resolution simulation in a 4527 km2 US Midwest basin using a physically-based, computationally efficient hydrologic-land surface model (PAWS+CLM). Results indicate that including more channels substantially alter the groundwater flow field and introduce large changes to hydrologic fluxes near the riparian zones. Upland ET is reduced and near-stream infiltration is enhanced due to the groundwater ‰ÛÏleaking‰Û effect of channels. Upland ecosystem production is quite sensitive to simulated channel density, forming a channel-influenced cone of decreased productivity that reaches far and wide into the basin. Systematic zonal analysis show that a given threshold, the cone increases in size dramatically. This studies helps choosing reasonable channel density in models and improve scale-aware surface flow formulations.

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