Improved unit hydrograph identification for seven Welsh rivers: implications for estimating continuous streamflow at ungauged sites

Hydrological Sciences Journal-journal Des Sciences Hydrologiques - HYDROLOG SCI J 01/2003; 48(5):743-762. DOI: 10.1623/hysj.48.5.743.51454

ABSTRACT A unit hydrograph-based continuous rainfall—streamflow model is applied at daily time step to several catchments in Wales. Two calibration methods are compared for seven catchments. Five of the catchments are among 60 basins in England and Wales for which models were derived by other investigators using the first calibration method, in order to devise a regionalization scheme allowing model parameters to be estimated from catchment properties. The paper shows that in several cases the first calibration method tends to overestimate low flows and give a positively biased estimate for one of the unit hydrograph parameters. It also shows that the second parameter calibration method can often overcome this problem, yielding model parameters more suitable for regionalization with respect to physical catchment properties. Implications of the work are discussed in the context of improving regionalization schemes where the estimation of streamflow in ungauged basins is the major objective.

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