Watershed characteristics and synthetic unit hydrographs determination using geographical information systems

Abstract

Precipitations and discharges are keys data in river watershed studies. In Nilüfer Dam Watershed, the flow values are measured every hour, whereas the cumulative rainfall values are recorded daily by the Public Water Management Department (DSİ). This study aimed to determine the characteristics of Nilüfer Dam Watershed and Synthetic Unit Hydrographs using Geographical Information Systems. The DSI synthetic method, Mockus method, and Snyder synthetic method were used in this study. For these three methods, the results showed a slightly significant difference between the discharge peaks of the resulting unit hydrographs. The highest discharge peak was achieved by the DSI Synthetic method (Qp = 4.40 m3/sec/mm) and the smallest by the Mockus method (Qp = 3.75 m3/sec/mm). The Mockus method achieved the longest basin lag time (Tp = 5.95 hours), and the shortest basin lag time was acquired by the Snyder method (Tp = 4.8 hours). This study suggests using synthetic methods for unit hydrographs determination in watersheds where there is no measured data.