Observed seasonal hydrological behaviour used in flow forecasting on the Yangtze River above Hankou

Abstract

Large catchments usually exhibit seasonal flow variation. The Linear Perturbation Model (LPM) of Nash and Barsi (1983) is an efficient tool to utilise this source of information for hydrological modelling. This paper briefly reviews the development of the model and presents the results of application to some catchments within the Yangtze River (known as Changjiang in China) basin. The flow forecasts at the outlets of each catchment are made principally by routing flows observed further up the catchment. To simulate intervening area inflow from rainfall, both linear models and a two-parameter conceptual water balance model are tested. On the catchment above Hankou alone, at which the LPM accounts for more than 50% of the residual variance of the simple linear model (SLM), the improved accuracy which could be obtained by allowing time variation of the LPM parameters has been studied and the results are presented. The paper concludes with the application of the LPM in real time forecasting mode.