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Uncertainty Analysis of SWAT Model Parameters using Monte Carlo Technique and Ensemble Flow Simulations

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  072208.(doi:10.13031/2013.23550)
Authors:   Phil-Shik Kim, Puneet Srivastava, Kyung H Yoo, Sun Joo Kim, Yaoqi Zhang, , ,
Keywords:   Uncertainty analysis, Monte Carlo simulation, Ensemble flow simulation, SWAT, Land use change

Abstract Mathematical models provide an alternative to field monitoring for evaluation of water quality and quantity. However, there is a degree of uncertainty associated with measured data and almost all landscape-based water quantity and quality models. Uncertainty is defined as the estimated amount by which an observed or calculated value may depart from the true value. However, quantifying the magnitude and impact of uncertainty and accounting for that uncertainty in the scenarios modeling process has not been sufficiently studied or implemented. This study evaluates the effect of uncertainty in input parameter on SWAT (Soil Water Assessment Tool) model output uncertainty using Monte Carlo Simulation (MCS). One hundred Monte Carlo simulations were performed to quantify the impact of input parameters for various land use scenario. Each 100 ensemble was generated with MCS results to analysis uncertainty using the SWAT model in Upper Cahaba River watershed in AL. Stream flow of replacing crop area and pasture were higher than mainly frost land use condition. The amount of flow in replaced crop by same ratio was higher than those of replaced pasture. The results uncertainties of parameters were great in order AWC, CN, GWREVAP and REVAPMN in all scenarios. Also, uncertainty in large forest area relatively were higher than that of pasture and crop area. Uncertainty of Initial modeling was much greater than those of scenarios application.

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