F LOOD FREQUENCY ASSESSMENT IN DATA POOR ENVIRONMENT C ASE STUDY M AGLAJ -P OLJICE ON THE RIVER B OSNA
. A truly important challenge in flood frequency assessment (FFA) in Bosnia and Herzegovina is lack of continuous gaged flow data, because the reliability of FFA results depends on the length and quality of flow records. At the case study location - hydrologic station (HS) Maglaj on the river Bosna the reference period for flow record is 1961-1990. The research goal in this paper is to exploit the water stage gauge data and information (1933-1960) for the extension of flow dataset from 30 to 58 years. We apply the original rating curve from the period 1960-1970 to the water table record to generate daily flow datasets. Anticipating three rating curve change developments, we generate six longer flow datasets -with and without instantaneous maxima, for the period 1933-1990 at HS Maglaj - Poljice. Together with two reference period flow datasets we arrive at the total of eight datasets/scenarios and subject these datasets to FFA on the annual maxima series and partial duration series. For the former, we use conventional statistical analysis (CSA) and for the latter, the peak over threshold (POT) method. The FFA results show no significant difference in the values of the selected quantiles for scenarios involving time extrapolation. The quantiles for the reference period 1961-1990 are generally higher, among both CSA and POT results. We find the absence of instantaneous maxima a major influence on FFA.