Simulation of Stream Flow in the Yantra River Basin, Bulgaria Via a GIS-based Modeling Approach

This paper describes the simulation of stream flow in ungauged watersheds using the computermodel BISTRA (Basin Impacts of Simulated Transport from Rural Areas), developed by the PennsylvaniaState University in collaboration with the Institute of Water Problems, Bulgarian Academy of Sciences. Themain purpose of this GIS-based model is the quantification of diffuse pollution loads at the catchment level.To achieve this, BISTRA contains a sub-model for simulating hydrology in a catchment based on genericclimate and landscape-related factors (e.g., daily precipitation and temperatures, soil, topography, land use,interdependence between surface and underground waters, etc.) which makes it possible to quantify monthlyrunoff, infiltration, and stream flow in areas where there are no gauge station records. The calibration andvalidation results for stream flow simulations conducted in the Yantra River basin in Bulgaria are given. Theconclusion is made that after calibration and validation, the model can be applied to determine the runoff andstream flow at different points of the river network where there are no gauge stations.