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Controls of land surface and bedrock topography on the spatial distributions of water table and storage: unifying saturation excess runoff models
  • Lili Yao,
  • Dingbao Wang
Lili Yao
University of Central Florida
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Dingbao Wang
University of Central Florida

Corresponding Author:[email protected]

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Abstract

The control of land surface topography on the configuration of groundwater table has been recognized and well explored. However, the control of bedrock topography on water table is much less studied, potentially due to the limited observations of bedrock. This paper evaluates the controls of both surface and subsurface topography on the spatial distributions of steady-state water table and the corresponding water storage at the catchment scale based on numerical simulations. Numerical models with different topographic features are developed using MODFLOW (USG). When water table is shallow, the control on the spatial distributions of water table is dominated by land surface topography (i.e., water table is approximately parallel to land surface); with the increase of water table depth, the role of land surface topography decreases; when water table is deep and close to bedrock surface, the spatial distributions of water table is dominated by bedrock topography (i.e., water table is approximately parallel to bedrock surface). For land surface-dominated water table, storage capacity in unsaturated area is spatially uniform, which is the underlying assumption of TOPMODEL; however, for bedrock-dominated water table, water storage in unsaturated area is spatially uniform, which is the underlying assumption of VIC-type model. The systematical variations of the controls of surface and subsurface topography on water table configuration provide a framework to unify saturation excess runoff models by treating TOPMODEL and VIC-type model as two endmembers.