Stream flow simulation within UK ungauged catchments using a daily rainfall-runoff model

One of the MOPEX science goals is to develop improved a priori model parameter estimation techniques for both large scale modelling applications and ungauged catchments. The access to daily stream flow data within ungauged catchments is also a central component of many aspects of water resource and water quality management.This paper explores the problem of regionalisation a rainfall-runoff model within the United Kingdom for water resources applications. The results from a regionalisation study using a large dataset of 260 catchments within the United Kingdom are presented.Two approaches to the regionalisation approach are developed and evaluated; a regression-based approach relating model parameters to catchment characteristics and a nearest neighbour based approach. The value of both approaches is evaluated in the context of the quality of the simulations obtained with regionalised parameter sets. The paper identifies that the regression-based approach yields the best predictive results and that these results are encouraging in the context of operational water management. However, the ultimate limitations of the approach are recognised and recommendations are made for further research on nearest neighbour approaches. The paper concludes by raising the question whether the regionalisation of the parameters for prior calibrated model is the most appropriate way to approach the regionalisation question and suggests an alternative modelling framework based on hydrological response units.