Low flow estimation for several durations and return periods using mean annual flow distribution
Résumé
The characteristics of low flow, in Timis-Bega hydrographical area, are presented in this paper. The low flow analysis will be done using the flow-duration-frequency (QdF) modelling, establishing for each analyzed sub-basin a local modelling associated to a Weibull Law with two parameters. Local modelling requires the knowledge of two local descriptors: the characteristic times of the low flow De and the median value of annual daily minima quantils. Based on these models, a dimensionless regional model for low flow was established. On other hand, the theoretical distribution of mean annual discharges was drawn for each analysed sub-basin using also Weibull Law with two parameters. Theoretical distribution comparison of dimensionless regional models corresponding to low and mean flow shows that these are almost identical. Thus a low flow estimation for several durations and mean return periods was tested, based on mean flow characteristics. The utilization of this method to the ungauged sites supposes the knowledge of two parameters of Weibull regional distribution corresponding to annual mean discharges, as well as an estimation of two local descriptors of low flow based on the river basin characteristics.