Frequency analysis of low flows in intermittent and non-intermittent rivers from hydrological basins in Turkey

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This study attempts to find out the best-fit probability distribution function to low flows using the up-to-date data of intermittent and non-intermittent rivers in four hydrological basins from different regions in Turkey. Frequency analysis of D = 1-, 7-, 14-, 30-, 90- and 273-day low flows calculated from the daily flow time series of each stream gauge was performed. Weibull (W2), Gamma (G2), Generalized Extreme Value (GEV) and Log-Normal (LN2) are selected among the 2-parameter probability distribution functions together with the Weibull (W3), Gamma (G3) and Log-Normal (LN3) from the 3-parameter probability distribution function family. Selected probability distribution functions are checked for their suitability to fit each D-day low flow sequence. LN3 mostly conforms to low flows by being the best-fit among the selected probability distribution functions in three out of four hydrological basins while W3 fits low flows in one basin. With the use of the best-fit probability distribution function, the low flow-duration-frequency curves are determined, which have the ability to provide the end-users with any D-day low flow discharge of any given return period.
Turkish National Meteorological and Hydrological Disasters Program (TUMEHAP) under the Turkish National Union of Geodesy and Geophysics (TUJJB)
This study is a part of the project entitled 'Analysis of Low Flow and Drought in Hydrological Watersheds' funded through the Turkish National Meteorological and Hydrological Disasters Program (TUMEHAP) under the Turkish National Union of Geodesy and Geophysics (TUJJB).