Modelling rainfall-discharge at a mean inter-yearly scale in northern Algeria

The aim of this work is to highlight the relationships between hydrological conditions and available surface water. The application has been carried out in northern Algeria, which has a surface area of 325,000 km2. The hydrological characteristics of surface flow which have been taken into account are climatic parameters (e.g. pluviometry, potential evapotranspiration, real evapotranspiration) and physical parameters (e.g. geology and topographical relief). The data from 467 pluviometric stations were used to generate the map of the median annual rainfall. This map was established by taking account of altitudes (Z) and geographical coordinates (longitude (X) and latitude (Y)). These parameters explain 67% of the variance in precipitation; the remaining 33% constitutes the residuals. There was a trend in the data and a second order stationary model was considered appropriate in order to permit the interpolation of the residuals by kriging. The grid of the residuals obtained is combined with the grids of different parameters highlighted by the regression model (longitude (X), latitude (Y) and altitude (Z)) in order to obtain a map of median annual rainfall. The study of the rain-discharge relationship on an inter-annual average scale is based on the observations made from 50 hydrometric stations distributed through the zone of study. This step consisted of establishing the relationship, which binds the discharge to the physical (geology) and climatic (median annual rainfall) parameters by using a multiple regression model. The results showed that 86% of the variation in discharge is explained by this model. Our study presents a model for rainfall-discharge in northern Algeria and provides a useful tool for hydrological management and evaluation of water resources.