A Second-Order Accurate, Finite Volume–Based, Integrated Hydrologic Modeling (FIHM) Framework for Simulation of Surface and Subsurface Flow

TLDR: In this article, a physics-based, distributed, fully coupled, second-order accurate, upwind cell-centered, constrained unstructured mesh based finite-volume modeling framework (FIHM) is presented.

Abstract: Surface water, the vadose zone, and groundwater are linked components of a hydrologic conƟ nuum. In order to capture the interacƟ on between diff erent components of a hydrologic conƟ nuum and to use this understanding in water management situaƟ ons, an accurate numerical model is needed. The quality of model results depends on accurate representaƟ on of the physical processes and the data describing the area of interest, as well as performance of the numerical formulaƟ on implemented. Here we present a physics-based, distributed, fully coupled, second-order accurate, upwind cell-centered, constrained unstructured mesh based fi nite-volume modeling framework (FIHM) that simultaneously solves two-dimensional unsteady overland fl ow and three-dimensional variably saturated subsurface fl ow in heterogeneous, anisotropic domains. A mulƟ dimensional linear reconstrucƟ on of the hydraulic gradients (surface and subsurface) is used to achieve second-order accuracy. Accuracy and effi ciency in raster data and vector-boundary representaƟ ons are facilitated through the use of constrained Delaunay meshes in domain discreƟ zaƟ on. The experiments presented here (i) explore the infl uence of iniƟ al moisture condiƟ ons, soil properƟ es, anisotropy, and heterogeneity in determining the pressure head distribuƟ ons in the vadose and saturated zones, (ii) show the existence of localized “fl ux rotaƟ on” phenomenon due to heterogeneous anisotropy, leading to the creaƟ on of convergence–divergence zones, (iii) show the infl uence of verƟ cal drainage from unsaturated zone on the response of an unconfi ned aquifer to pumping, and (iv) show the eff ects of capillarity, saturaƟ on excess, infi ltraƟ on excess, and iniƟ al water table locaƟ on on determining the overland fl ow generaƟ on.