An integrated design discharge calculation system for small to mid-sized ungauged catchments in Serbia

Abstract. This study deals with the application of freely available datasets on the global and local level coupled with open source GIS software in hydrological modelling, greatly improving cost and time effectiveness of hydrological analyses of ungauged catchments. The automated calculation system was developed as an extremely useful tool for hydrologists for the quick estimation of design discharges. The morphometric module of the calculation system showed excellent results, saving a great deal of time that would otherwise been spent on manual processing of geospatial data. Using the automated calculation system, the methodologies currently in use in hydrological practice in Serbia were evaluated. The distributed velocity method was introduced as a way of calculating hydrograph lag time. The comparison between design discharges calculated by rainfall-runoff analysis and by frequency analysis yielded very good resemblance. Examples of real-world application for over 2500 catchments are shown.