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Abstract. Following the Budyko framework, the soil wetting ratio (the ratio betweensoil wetting and precipitation) as a function of the soil storage index (theratio between soil wetting capacity and precipitation) is derived from theSoil Conservation Service Curve Number (SCS-CN) method and the variableinfiltration capacity (VIC) type of model. For the SCS-CN method, the soilwetting ratio approaches 1 when the soil storage index approaches ∞,due to the limitation of the SCS-CN method in which the initial soil moisturecondition is not explicitly represented. However, for the VIC type of model,the soil wetting ratio equals the soil storage index when the soil storageindex is lower than a certain value, due to the finite upper bound of thegeneralized Pareto distribution function of storage capacity. In this paper,a new distribution function, supported on a semi-infinite interval , is proposed for describing the spatial distribution of storagecapacity. From this new distribution function, an equation is derived for therelationship between the soil wetting ratio and the storage index. In thederived equation, the soil wetting ratio approaches 0 as the storage indexapproaches 0; when the storage index tends to infinity, the soil wettingratio approaches a certain value (≤1) depending on the initial storage.Moreover, the derived equation leads to the exact SCS-CN method when initialwater storage is 0. Therefore, the new distribution function for soil waterstorage capacity explains the SCS-CN method as a saturation excess runoffmodel and unifies the surface runoff modeling of the SCS-CN method and theVIC type of model.
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Climatic Control on Spatial Distribution of Water Storage at the Catchment Scale: A Framework for Unifying Saturation Excess Runoff Models
Abstract This paper aims to investigate the connection between TOPography‐based hydrological model (TOPMODEL) and Variable Infiltration Capacity (VIC) model through virtual experiments from the perspective of water table and storage at the catchment scale. A simple finite‐difference groundwater flow model was built for a hypothetical catchment forced by a sequence of recharges. A steady‐state water table under a low recharge rate is used as the climatic lower limit, above which the pore space is considered as the maximum storage capacity. When the water table is shallow, the land surface is a good proxy of the water table as assumed in the original TOPMODEL, and the underlying water storage distribution curve is similar as the maximum storage capacity distribution curve. When the water table is deep, the climatic lower limit is a good proxy of water table, and the storage is approximately spatially uniform over the unsaturated area as assumed in the VIC model. The systematic variation of water table and storage distribution potentially provides a framework for unifying the TOPMODEL and VIC model.
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- Award ID(s):
- 1804770
- PAR ID:
- 10444481
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 127
- Issue:
- 10
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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