Influence of record length on flow duration curve

Flow duration curve is widely applied in water resource projects. The shape of flow duration curve will change with record length and incline to be stable with an increasing record length. In this work, we employ multivariate statistics of analysis to investigate the influence of record length on the flow duration curve. Ten stream gauge stations having nearly three decades of record length in southern Taiwan supply the data set in the paper. A flow duration curve was found to be well depicted by first two principal components and plotted as a `point' in the diagram of principal component. In addition, the difference between any flow duration curves derived by short and long record lengths can be discussed in the diagram of principal component. Based on the results presented herein, we can conclude that the flow duration curve constructed by ten years of record length has nearly 20% error with the flow duration curve derived by the all of record length.