An enhanced SWAT wetland module to quantify hydraulic interactions between riparian depressional wetlands, rivers and aquifers

Mohammed M Rahman,Julian R Thompson,Roger J Flower

doi:10.1016/j.envsoft.2016.07.003

Mohammed M Rahman, Julian R Thompson + Show 1 more

Open Access

https://doi.org/10.1016/j.envsoft.2016.07.003

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Abstract

This study develops a modified version of the Soil and Water Assessment Tool (SWAT) designed to better represent riparian depressional wetlands (SWATrw). It replaces existing unidirectional hydrological interactions between a wetland and a river/aquifer with a more robust bidirectional approach based on hydraulic principles. SWATrw incorporates a more flexible wetland morphometric formula and a connecting channel concept to model wetland-river interactions. SWAT and SWATrw were tested for the Barak-Kushiyara River Basin (Bangladesh and India). Although the two models showed small differences in simulated stream flow, SWATrw outperformed SWAT in reproducing river stages and the pre-monsoon river-spills into riparian wetlands. SWATrw showed that the observed presence of dry season water in the wetland was due to reduced seepage to the local groundwater table whilst continuous seepage simulated by SWAT resulted in the wetland drying out completely. The new model therefore more closely simulates the hydrological interactions between wetlands, rivers and groundwater.

Highlights

Name of software: SWAT2012 (Soil and Water Assessment Tool) Developer: USDA Agricultural Research Service (USDA-ARS) andTexas A&M AgriLife Research Contact address: 808 E Blackland Rd, Temple, TX 76502, UnitedStates, Phone: þ1 254-770-650; http://blackland.tamu.edu/models/swat/ Year first available: 2012 Hardware required: PC Software required: ArcGIS Program language: FORTRAN Program size: 3.1 MB Availability and cost: Freely available at http://swat.tamu.edu/software/swat-executables/
A geographically isolated wetland (GIW) which is completely surrounded by upland areas to form a depressional system (Golden et al, 2014) can have strong interactions with underlying groundwater systems depending on the hydraulic properties of the underlying substrate (Fan and MiguezMacho, 2011; Golden et al, 2014; Hollis and Thompson, 1998; Pyzoha et al, 2008; Restrepo et al, 1998)
If the wetland is poorly connected with local river systems, it will have negligible influences on downstream flows compared to a riparian wetland in close hydraulic contact with a river channel (Ogawa and Male, 1986; Sun et al, 2004)

Summary

Introduction

Name of software: SWAT2012 (Soil and Water Assessment Tool) Developer: USDA Agricultural Research Service (USDA-ARS) andTexas A&M AgriLife Research Contact address: 808 E Blackland Rd, Temple, TX 76502, UnitedStates, Phone: þ1 254-770-650; http://blackland.tamu.edu/models/swat/ Year first available: 2012 Hardware required: PC Software required: ArcGIS Program language: FORTRAN Program size: 3.1 MB Availability and cost: Freely available at http://swat.tamu.edu/software/swat-executables/. M.M. Rahman et al / Environmental Modelling & Software 84 (2016) 263e289 this supposed flow reduction ability is not applicable to all wetlands and is influenced by factors that include the location of wetlands within a catchment, their geometry and storage capacity, antecedent storage and the nature and degree of hydraulic connectivity with adjacent water bodies such as rivers and underlying aquifers. If the wetland is poorly connected with local river systems, it will have negligible influences on downstream flows compared to a riparian wetland in close hydraulic contact with a river channel (Ogawa and Male, 1986; Sun et al, 2004). As a result of this interaction with other water bodies riparian wetlands generally exhibit more complex hydrological behaviour than GIWs with inflows from rivers and runoff from upland areas occurring more rapidly than groundwater exchanges (Walton et al, 1996)

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