determincation and evaluation of runoff coefficients of basins by using geographical information systems

turkey has very different geomorphologic hydrologic and climatic conditions so the runoff coefficient should be different from one basim to another but only a constant value 0.37 is being used for all the basins in turkey in this study monthly seasonal and annual runoff coefficients of 48 sub -basins in western and southern part of anatolia are determined by using synchronous rainfall -runoff data of 26 years record period and their temporal and spatial distributions are investigated . the relationship between the basin parameters and the runoff coefficient is also examined.