Modelling of base flows by analysing the streamflow hydrograph

During dry periods, the flow of medium and small streams is significantly reduced and equal to groundwater flow. Since the base flows provide information about aquifer characteristics and retention characteristics of a basin, the possibilities of analysis and simulation of base flows gain importance under the conditions of intensive water use and the increasing demand for adequate water quality protection. In this paper, a model was established and used for the description of the principles governing the changes of base runoff on the basis of a streamflow hydrograph registered at the outlet of the basin on the example of the Kolubara basin up to the ?Valjevo? profile. Since the amount of base runoff from a basin cannot be measured, the results of base flows obtained using the local minimum method were adopted as the criterion for the comparison of the modelled values of base runoffs. The created model was applied for making simulations of the base runoff hydrograph during three characteristic years (rainy 1970, average 1985, and dry 1990). Deviations between the base flow values obtained using the established model and by applying the local minimum method are acceptable from the standpoint of general hydrological accuracy.