A soil-based approach to rainfall-runoff modelling in ungauged catchments for England and Wales

摘要

Hydrological models are powerful tools for the investigation of manyhydrological issues. The historical approach for the development of rainfall-runoffmodels, with regard to the choice of model structure and the calibration of the freeparameters, has been to focus on gauged catchments where sufficient data, in particularstream flow data, are available. Applications of models were then extended to the caseof ungauged catchments. In recent years, it has become apparent that this approach didnot lead to satisfying results in ungauged catchments, and that the main focus shouldinstead be on ungauged catchments for the implementation of new modelling strategies.This thesis demonstrates the potential of a new conceptual, catchment-scale,semi-distributed, integrated rainfall-runoff model as a modelling tool in both ungaugedand gauged catchments for the assessment of water resources management, land usechange or climate changes at the catchment scale.The review of existing model structures and regionalisation methods has lead tothe development of the Catchment Resources and Soil Hydrology (CRASH) modelfollowing the top-down modelling strategy. The free parameters of the model aredirectly related to controlling factors of the hydrological processes in the UnitedKingdom, i.e. soil and land use. The classification of the soils according to theirhydrological behaviour is based on the Hydrology Of Soil Types (HOST) system.CRASH also incorporates a novel rainfall disaggregation scheme for the derivation ofinfiltration excess surface runoff.A regional set of model parameters has been derived from the calibration ofCRASH in 32 catchments throughout England and Wales covering contrasting climatic,soil, geological, and land use conditions.The single-site and regional CRASH models performed satisfactorily accordingto reviewed performance criteria for gauged catchments and to a scoring systemproposed for ungauged catchments. However the quality of stream flow data in the UKwhich was used for the calculation of the regional parameter set, in particular thewidespread unavailability of naturalised flow data, tends to limit the performance of theregional CRASH model for low flows.