Hydrological Water Balance Model for Modelling the Natural River Flow of Rivers in Bulgaria

The ability to collect, transform, store, and process significant arrays of environ-mental data, together with the available computing systems and models, provided the opportunity to develop and sustainably use physical water balance models for simulating river runoff in Bulgaria. The applications of these models in the field of hydrological forecasting, water balance studies, climate change, as well as in the research process at the National Institute of Meteorology and Hydrology (NIMH) have over 15 years of history. The paper exam-ines the variants of such systems used by NIMH, giving specific application cases: river flow forecasting, computation of water balance, simulation of extreme hydrological events. Some results of linking a physical deterministic model for the land surface (ISBA, SURFEX) and a conceptual model for runoff routing in the river network (Modcou, TOPMODEL, RAPID) are presented.