A Wetland Simulation Module for the MODFLOW Ground Water Model

Abstract

The alteration of wetland habitats by natural and anthropogenic processes is an issue of worldwide concern. Understanding the changes that occur in wetlands often requires knowledge of how surface water levels relate to adjacent aquifer systems. The ability to simulate surface water movement and its interaction with ground water and wetland slough channels is a desirable step in the design of many projects constructed in or near wetlands. Currently, most ground water flow models incorporate wetland systems as general head boundary nodes. The purpose of this research was to develop a computer package for the widely used MOD‐FLOW code that would simulate three‐dimensional wetland flow hydroperiods and wetland interactions with aquifers and slough channels. The ground water flow model was used to reproduce the surface water flow process through wetlands, and then to estimate new flow rates and values using a Manning‐type equation. This package represents flow routing, export and import of water, and evapotranspiration from wetlands for different hydroperiods. A basic verification procedure for the numerical solution of the diffusion equation was applied, based on a test case that was solved using a two‐dimensional surface water model. This example is a transient solution to the diffusion equation, in which the initial conditions were depicted by a sinusoidal water surface profile and a flat bottom.

A water-table dependent reservoir model to investigate the effect of drought and vascular plant invasion on peatland hydrology

“…Frequent WT drawdowns creating a deeper and thicker acrotelm than is observed in intact peatlands may lead to further degradation and to a reinforcement of the runoff generation by erosion phenomena, change the water quality (Daniels et al, 2008) and modify evapotranspiration (Restrepo et al, 1998). This is also evidenced in harvested sites where drainage and peat extraction lower the WT, expose relatively decomposed peat and increase the runoff (Van Seters and Price, 2001), whereas creating artificial drain blocking increases the WT, modifies the runoff and the water quality (Worrall et al, 2007).…”

“…To do so, hydrological peatland models are based on the regular concept of soil hydrology (Restrepo et al, 1998). For large scale areas and for geochemical modeling, hydrologists usually prefer to apply a reservoir model with a limited number of calibrated parameters (Perrin et al 2001;Violette et al, 2010).…”

Applying MODFLOW to wet grassland in-field habitats: a casestudy from the Pevensey Levels, UK

“…cell re-wetting or spatially variable anisotropy). A wetland module is available (Restrepo et al, 1998), although this was developed for swamp areas rather than grass wetlands. Commercial versions of MODFLOW provide a comprehensive suite of techniques to assist model design, to input data and analyse and present model output.…”

Five-year summary and evaluation of operations and performance of the Utica aquifer and North Lake Basin Wetlands restoration project in 2004-2009.

“…The HSPF watershed hydrology code (Bicknell et al 1997) was used with distributed flow model simulations by the WETMOD wetland flow module of MODFLOW (Restrepo et al 1998;McDonald and Harbaugh 1988) to establish relationships among precipitation, runoff, and surface water infiltration in the basin. The model output was combined with simulations by a lumpedparameter water-energy balance model (Argonne 2000) to evaluate effects of various water supply scenarios.…”