The river discharge is an essential component for hydrologic analysis and water resources management. Therefore, it is importa nt to measure the discharge reliably. While the rainfall and water level in the river can be observed continuously and automatically, it is difficult to measure the river discharge continuously due to the limitations of technological and economical reasons. Thus the stage-discharge curve has been being used to obtain the discharge instead of measuring the discharge directly. However, in case of the estimation of discharge through a stage-discharge relation, there would be many errors occurring while converting and analyzing data. Therefore, we need the analysis for the reduction of the uncertainties or errors involved in stage-discharge relation, then, the reliable discharge can be estimated.
In this study, the parameters estimated by Bayesian and Bootstrap methods have been compared with the ones obtained by stage-discharge relation curve that is provided by Ministry of Land, Infrastructure, and Transport. In addition, the Bayesian and Bootstrap methods have been applied to assess uncertainty and then those are compared with the confidence intervals of the result from standard error method which has t-distributions. When calculating the confidence intervals with t-distributions, it tends to be overestimated at high water level. When using the Bayesian and Bootstrap methods, on the other hand, the confidence intervals is 5~9% less than the existing method. That means the Bayesian and Bootstrap methods have less errors to estimate the confidence intervals. From the results of this study, we show that the confidence interval by t-distributions is more suitable for the regions with small number of data and small standard deviation while the Bayesian and Bootstrap methods are suitable for the regions with small number of data and large standard deviation. Therefore, if we use more suitable method according to the river characteristics, we could obtain more reliable discharge with less uncertainty.

Keywords : Bayesian method, Bootstrap method, Uncertainty, Stage-Discharge curve