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Abstract: Prediction in ungauged basins remains a major challenge in hydrology. A key issue in the application of hydrological models to ungauged areas is regional parameterization. This paper presents a regional calibration approach to constructing regional relationships between the parameters of the Snowmelt-based Water Balance Model (SWBM) and catchment characteristics. Data from 38 well-gauged catchments were used to establish regional regression equations of model parameters, and data from an additional four independent catchments were used to test and validate the proposed regional calibration approach. The results indicated that the SWBM performed well in monthly discharge simulations for the 38 well-gauged catchments. The regional relationships of the SWBM parameters derived from the regional calibration approach were found to be highly correlated to catchment characteristics. In addition, the SWBM performed well in discharge simulations for the additional four test sites using only the constructed regional equations to estimate model parameters. [Copyright &y& Elsevier]

Accurate estimates of the uncertainties associated with hydrological model are essential for better streamflow simulation. This paper explores the Ensemble Kalman Filter (EnKF), an ensemble data assimilation method, for semi-distributed hydrological model updating. The semi-distributed model is very practical and often used for moderate and large basin streamflow forecasting and water resources management. The studied area in this study is a large basin of Baohe, upper branch of Hanjiang River. The semi-distributed Xinanjiang model states are updated by assimilating several spatially distributed measurement points within the whole basin. The spatial pattern and ensemble of model states such as soil water content are derived. A lumped model updating case is taken for comparison. The results show that the semi-distributed model case does better in high flow simulation than the lumped case, with 16% and 25% improvement to the simulation performance at peak flow in two periods of heavy rain processes. The smaller streamflow uncertainty at main basin outlet is also found in the semi-distributed updating case. [ABSTRACT FROM AUTHOR]

Abstract: Long monthly streamflow series of three control hydrological stations of the Pearl River basin were analyzed by using the scanning t-test and the scanning F-test. Possible implications of the changing properties of streamflow variations for the water resource management of the Pearl River Delta are also discussed. The results indicated that: 1) more complicated changes were observed in terms of the second center moment when compared to the first original moment. More significant abrupt changes of the second center moment imply more sensitive response of streamflow stability to climate changes and human activities; 2) abrupt behaviors of the first (second) center moment of the streamflow variations tend to be more sensitive to climate changes and/or human activities in the larger river basin when compared to those in the smaller river basin. These phenomena are attributed to buffering functions of more storage space of longer river channel, and more complicated and longer runoff yield and concentration processes in the river basin of larger drainage area; 3) annual minimum streamflow of the Pearl River basin tends to be increasing. This will be helpful for better human mitigation of the salinity intrusion in dry seasons across the Pearl River Delta. Annual maximum streamflow, when compared to annual minimum streamflow, shows larger-magnitude variability reflected by larger standard deviation, implying unfavorable conditions for flood mitigation in the Pearl River Delta. The results of this paper are of scientific and practical merits for water resource management and sound human mitigation to water hazards across the Pearl River Delta, and also are a good case study for similar researches in other river deltas in the world under the changing environment. [ABSTRACT FROM AUTHOR]