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Sensitivity analysis of hydraulic conductivity and Manning’s n parameters lead to new method to scale effective hydraulic conductivity across model resolutions.

Authors: Maxwell, R. M.; Foster, L.
Year: 2019
Journal: Hydrological Processes, Vol. 33, pp. 332-349

Abstract

Hydrological modeling is an important tool for research, policy, and management, but uncertainty remains about parameters transferability from field observations made at small scale to models at the catchment scale and larger. This uncertainty compels the need to develop parameter relationships that are translatable across scale. In this study we compare the changes to modeled processes as resolution is coarsened from 100m to 1km in a topographically-complex, 255km2 Colorado River headwater catchment. We conducted a sensitivity analysis for hydraulic conductivity (K) and Manning’s n parameters across 4 orders of magnitude. Results showed that K acts as a moderator between surface and subsurface contributions to streamflow, while n moderates the duration of high intensity, infiltration-excess flow. The parametric sensitivity analysis informed development of a new method to scale effective hydraulic conductivity across modeling resolutions in order to compensate for the loss of topographic gradients as resolution is coarsened. A similar mathematical relationship between n and lateral resolution changes was not found, possibly because n is also sensitive to time discretization. This research provides an approach to translate hydraulic conductivity parameters from a calibrated coarse model to higher resolutions where the number of simulations are limited by computational demand.

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