Estimation of Flow Duration Curve at Ungauged Locations in Taiwan

Flow duration curves (FDCs) are widely used to assess water availability. With the aim of overcoming the scarcity of available data in many river basins, this study proposed a process to estimate FDCs at ungauged locations. Twenty-two river basins in Taiwan with major demands were analyzed through multivariate statistical techniques. First, 158 gauges were grouped into homogeneous regions using principal component analysis (PCA), cluster analysis (CA), and discriminant analysis (DA). Second, 99 gauges with data containing unregulated flow were selected and models were built for FDC estimations, applying three regression methods including the traditional multiple linear regression (MLR), principle component regression (PCR), and partial least-squares regression (PLSR). A comparison of the model performances obtained using a cross-validation procedure showed some unstable conditions for MLR in the regional regression models for estimating the FDC; this was due to the variation of selected variables among percentile flows. The PCR and PLSR approaches can address the difficulties of variable selection and achieve a more-robust model of FDC estimation.