Turkish Journal of Engineering and Environmental Sciences

Abstract: In this research, a stable environmental isotope study was carried out from an analysis of water samples collected from rainfall, runoff (total discharge), springs (subsurface flows) and wells (groundwater) between 1996 and 2000. The research site was the Güvenç Basin located near Yenimahalle-Ankara with a drainage area of about 16.125 km². The aim of the study was to investigate the rainfall-runoff relationship for the Güvenç Basin using the stable isotope method in the separation of hydrographs. Recorded total discharge hydrographs are separated into their components using isotopes (oxygen-18, deuterium) contents. Among these samples, unit hydrographs from 2 single-peaked storm hydrographs were derived using both isotope and graphical (Barnes semi-log) methods and the derived unit hydrographs' peaks were compared. It was found that the contribution of subsurface flow originating from various sublayers of the basin is important in hydrograph separation when using the isotope method of approach.

Key Words: Hydrograph separations, Stable isotopes, Graphical method, Unit hydrograph.