An Integrated Media, Integrated Processes Watershed ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

An Integrated Media, Integrated Processes Watershed Model – WASH123D: Part 3 –a comparative study on different surface water/groundwater coupling approaches
Author:GUOBIAO HUANG <> (Sutron Corporation, West Palm Beach, FL, USA)
Gour-Tsyh Yeh <> (Dept of Civil and Environ. Eng., Univ. of Central Florida, Orlando, FL, USA)
Presenter:GUOBIAO HUANG <> (Sutron Corporation, West Palm Beach, FL, USA)
Date: 2006-06-18     Track: General Sessions     Session: General

In the core of an integrated watershed model is the coupling among surface water and subsurface water flows. Recently, there is a tendency of claiming the fully coupled approach for surface water and groundwater interactions in the hydrology literature. One example is the assumption of a gradient type flux equation based on Darcy’s Law (linkage term) and the numerical solution of all governing equations in a single global matrix. We argue that this is only a special case of all possible coupling combinations and if not applied with caution, the non-physical interface parameter becomes a calibration tool. Generally, there are two cases based on physical nature of the interface: continuous or discontinuous assumption, when a sediment layer exists at the interface, the discontinuous assumption may be justified. As for numerical schemes, there are three cases: time-lagged, iterative and simultaneous solutions. Since modelers often resort to the simplest, fastest schemes in practical applications, it is desirable to quantify the potential error and performance of different coupling schemes. We evaluate these coupling schemes in a finite element watershed model, WASH123D. Numerical experiments are used to compare the performance of each coupling approach for different types of surface water and groundwater interactions. These are in term of surface water and subsurface water solutions and exchange flux (e.g. infiltration/seepage rate). It is concluded that different coupling approaches are justified for flow problems of different spatial and temporal scales and the physical setting of the interface.