Parameterization based on NOAA-AVHRR NDVI to improve conceptual rainfall- runoff modelling in a large West African catchment

摘要

A conceptual hydrological model (GR2M) is applied to a large, poorly gauged catchment in West Africa. The purpose is to simulate the rainfall-runoff relationship at a monthly time step over the period 1982-2000 during which marked hydro-climatic changes took place. The model is based on two parameters: XI for the production function and X2 for the routing function. The size of the production reservoir is usually fixed over time by using data from the FAO soil map. Hydroclimatic data consist of observed series of rainfall, PET and discharge data. The advantage of calibrating the size of the production reservoir by using spatiotemporal satellite NDVI data from NOAA-AVHRR images is investigated. Indeed, in a context of substantial climatic variability, or even of non-stationarity of the observed series, it may be difficult for conceptual models to reproduce runoff precisely over long periods of time. Introducing a spatiotemporal vegetation signal using NDVI data enables partial capture of the effect of the climatic and environmental variability on the functioning of the catchment. Calibrating the model using these additional forcing data significantly enhances the simulation results at the basin outlet, whatever the spatial complexity considered within the watershed through lumped or semi-distributed applications of the model. This study is a first step towards the design of a production function accounting for the spatiotemporal variability of a vegetation index.