Abstract
Ten years after the Predictions in Ungauged Basins (PUB) initiative was put forward, known as the post-PUB era (2013 onwards), reducing uncertainty in hydrological prediction in ungauged basins still receives considerable attention. This integration or optimization of the traditional regionalization approaches is an effective way to improve the river discharge simulation in the ungauged basins. In the Jialing River, southwest of China, the regression equations of hydrological model parameters and watershed characteristic factors were firstly established, based on the block-wise use of TOPMODEL (BTOP). This paper explored the application of twelve regionalization approaches that were combined with the spatial proximity, physical similarity, integration similarity, and regression-augmented approach in five ungauged target basins. The results showed that the spatial proximity approach performs best in the river discharge simulation of the studied basins, while the regression-augmented regionalization approach is satisfactory as well, indicating a good potential for the application in ungauged basins. However, for the regression-augmented approach, the number of watershed characteristic factors considered in the regression equation impacts the simulated effect, implying that the determination of optimal watershed characteristic factors set by the model parameter regression equation is a crux for the regression-augmented approach, and the regression strength may also be an influencing factor. These findings provide meaningful information to establish a parametric transfer equation, as well as references for the application in data-sparse regions for the BTOP model. Future research should address the classification of the donor basins under the spatial distance between the reference basin and the target basin, and build regression equations of model parameters adopted to regression-augmented regionalization in each classification group, to further explore this approach’s potential.
Highlights
Licensee MDPI, Basel, Switzerland.An ungauged basin is a relative concept, which mainly refers to a basin lacking high temporal and spatial resolution, long historical records, and continuous ground precipitation and river flow data [1,2]
It is necessary to conduct an overall evaluation of the river discharge simulation results of the regionalization approaches for each ungauged basin
Relying on the nine processed watershed characteristic factors (including two new characteristic factors: mean soil particle size (Φ) and mean root depth (r)), this study carried out correlation analysis on the five model parameters of the block-wise use of TOPMODEL (BTOP) model
Summary
An ungauged basin is a relative concept, which mainly refers to a basin lacking high temporal and spatial resolution (higher observing site density), long historical records, and continuous ground precipitation and river flow data [1,2]. Due to the limited number of hydrological and meteorological observations, plenty of ungauged basins are widely distributed worldwide, especially in developing countries. These small and medium-sized basins are more common and typical ungauged basins, due to natural conditions or social and economic constraints [1,4,5]. Discharge simulation is an essential part of water resources management [6], water environment protection [7] and risk management [8]
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