Modelling of base flow of the basin of Kolubara river in Serbia

SummaryThis study presents a physically founded hydrologic–hydraulical model for determining the base flow of the catchment by analysing the water balance of the basin and vertical exchange of water between the atmosphere, unsaturated media and ground water, basing on the known physical characteristics of the basin (climatic, paedological, geological and vegetation ones) on the example of the 340 km2 Kolubara River basin up to “Valjevo” water level monitoring station in Serbia in three characteristic years: an extremely rainy year (1970), an average year (1985) and an extremely dry year (1990).Taking into consideration that the amount of base flow of a basin is impossible to measure at the catchment outlet, the hydrograph of the base flow values obtained by separating from the streamflow hydrograph registered at the outlet of a drainage basin by application of the graphical local minimum method was used for checking the model’s functioning.It was finally determined that the total base flow values at the outlet point of the catchment, obtained by application of the graphical local minimum method, equal approximately the total groundwater recharge from the whole surface area of the basin, representing the summary of groundwater recharge originating from different soil types covered with different types of vegetation, under the influence of atmospheric conditions of the soil surface. Thus it was confirmed that when characteristics of a basin are known, it is possible to obtain information on the base flow values.