Evaluation of the Effect of Channel Geometry on Streamflow and Water Quality Modeling and Modification of Channel Geometry Module in SWAT: A Case Study of the Andong Dam Watershed

Jeongho Han,Se-Woong Chung,Seoro Lee,Minji Park,Dongjun Lee,Kyoung Lim,Jonggun Kim,Seong Kim

doi:10.3390/w11040718

Abstract

The impact of the channel geometry on water quantity and quality simulation of the Soil and Water Assessment Tool (SWAT) was evaluated for the Andong Dam watershed. The new equations to determine the bankfull width of the channels and the bottom width of the floodplains were developed using aerial photographs, and its performance was compared with the current equations of SWAT. The new equations were more exact than the current equations since the current equations tended to overestimate the widths of the channel and floodplain. When compared with the observed data, the streamflow of the scenario 2 (S2, applying the new equations) showed lower deviation and higher accuracy than scenario 1 (S1, applying the current equations) because the peak flow of S2 captured the observed data better due to the impact of the change geometry. Moreover, the water quality results of S2 outperformed S1 regarding suspended solid, total nitrogen, and dissolved oxygen. This is attributed to the variables, such as flow travel time, which is directly related to the channel geometry. Additionally, SWAT was modified to consider the various channel cross-sectional shapes. The results of this study suggest that the channel geometry information for the water quantity and quality estimation should be carefully applied, which could improve the model performance regarding streamflow and water quality simulations.

Highlights

Various studies have been conducted to predict the hydrology and water quality for river and watershed management in ungauged watersheds
The average channel bankfull width and the average floodplain bottom width data for each sub-watershed, which were calculated from the channel geometry data measured by Google Earth Pro, were applied to the CurveExpert program to develop the regression equations
The new regression equations were expressed as a function of the upstream watershed area

Summary

Introduction

Various studies have been conducted to predict the hydrology and water quality for river and watershed management in ungauged watersheds. Nonpoint Sources (BASINS), and Soil and Water Assessment Tool (SWAT) [1] These hydrological models generally simulate the streamflow and water quality by calculating various parameters based on input data such as topographic and meteorological data [2,3]. In addition to the parameters calculated using the topographic and meteorological data (e.g., curve numbers, elevation, slope, and soil properties), the hydraulic characteristics of the channels in watersheds play a crucial role in the water quantity and quality simulation as well as habitat evaluation since they are important influential factors [4,5] For this reason, in most hydrological models, the channel shape parameters (e.g., channel width, depth, slope, length, and floodplain width) are required as input parameters [6]. In most hydrological models, the channel width and depth are estimated using the regression equations for the upstream watershed area [8,9,10,11]

Objectives

Methods

Results

Conclusion