Comparison of Natural Flow Estimates for the Han River Basin Using TANK and SWAT Models

Abstract

Two models, TANK and SWAT (Soil and Water Assessment Tool) were compared for simulating natural flows in the Paldang Dam upstream areas of the Han River basin in order to understand the limitations of TANK and to review the applicability and capability of SWAT. For comparison, simulation results from the previous research work were used. In the results for the calibrated watersheds (Chungju Dam and Soyanggang Dam), two models provided promising results for forecasting of daily flows with the Nash-Sutcliffe model efficiency of around 0.8. TANK simulated observations during some peak flood seasons better than SWAT, while it showed poor results during dry seasons, especially its simulations did not fall down under a certain value. It can be explained that TANK was calibrated for relatively larger flows than smaller ones. SWAT results showed a relatively good agreement with observed flows except some flood flows, and simulated inflows at the Paldang Dam considering discharges from upper dams coincided with observations with the model efficiency of around 0.9. This accounts for SWAT applicability with higher accuracy in predicting natural flows without dam operation or artificial water uses, and in assessing flow variations before and after dam development. Also, two model results were compared for other watersheds such as Pyeongchang-A, Dalcheon-B, Seomgang-B, Inbuk-A, Hangang-D, and Hongcheon-A to which calibrated TANK parameters were applied. The results were similar to the case of calibrated watersheds, that TANK simulated poor smaller flows except some flood flows and had same problem of keeping on over a certain value in dry seasons. This indicates that TANK application may have fatal uncertainties in estimating low flows used as an important index in water resources planning and management. Therefore, in order to reflect actually complex and complicated physical characteristics of Korean watersheds, and to manage efficiently water resources according to the land use and water use changes with urbanization or climate change in the future, it is necessary to utilize a physically based watershed model like SWAT rather than an existing conceptual lumped model like TANK.

Development and Verification of the Available Number of Water Intake Days in Ungauged Local Water Source Using the SWAT Model and Flow Recession Curves

“…The SWAT is a program developed by Dr. Jeff Arnold of the United States Department of Agriculture Agricultural Research Service (USDA ARS) for analyzing long-term hydrologic and water quality changes in large and complex watersheds with diverse soil properties and land uses [14]. The SWAT model is a semi-distributed long-term flow model that is more efficient as a dry season model compared with the Tank model and is more reliable than other semi-distributed models, such as the Precipitation-Runoff Modeling System (PRMS) model and the Hydrological Simulation Program-Fortran (HSPF) model [45,46]. Hence, this model was selected for this study as it has also been tested for its applicability to various areas in Korea and universal applicability to studies on surface flow, riverbed, lake, and underground water.…”

Parameter Regionalization of a Tank Model for Simulating Runoffs from Ungauged Watersheds

“…국내에서 미계측 유역의 유출이나 저수지 및 댐의 유입 량은 가지야마 공식, 다중회귀모형, Tank 모형, SWAT 모형 등을 이용하여 추정되어 왔다 (Yoon and Wone, 1991;Noh, 1999;Kang et al, 2002;Noh, 2003;Kim and Kim, 2012). 특히 가지야마 공식은 모형의 편리 성으로 인하여 저수지의 월유입량 산정에 많이 이용되어 왔으며, 다른 모형들의 정확성 평가에 비교대상으로 이용 되기도 했다.…”