Basin-Wide Water Balance in the Danube River Basin

This paper briefly describes the result of mutual work of the IHP UNESCO National Committees of the Danube countries and experts and scientists nominated by their countries. It represents part of the second phase of the co-operation of Danube countries within the frame of the IHP UNESCO in the field of hydrology. This project in fact represents a continuation, improvement and enlargement of the first Danube Monograph (Stan'elk et al. 1988, Hydrology of the River Danube, Publishing House Prfroda, Bratislava). The main objectives of the work were estimation of water balance components on the basis of mathematical modelling and preparation of maps of water balance components for the Danube Basin. Maps of the mean annual precipitation, actual evapotranspiration and runoff were prepared. Difficulties in data collection in individual countries resulted in the obligatory period for data analysis of 1961-1990. The first part of this work presents the administrative background and circumstances which favourably helped to intensify work on the project since 2002. The second part deals with assessment of the general water balance of the Danube River Basin. In terms of working maps, the USGS (US Geological Survey) HYDRO lk digital terrain model was chosen. The Danube area was split into 109 balance regions. The intention was to apply the water balance model WatBal to each such region to calculate evapotranspiration for the balance regions as the main output. The third part deals with monthly data collection and processing, WatBal model methodology and with model tuning. Calculation of water balance was performed for 109 balance regions, but tuning was successful for 84 balance regions only. Results are given both in a tabular and map form.