comparison of two rainfall – runoff models for simulation of stream flow (case study: doiraj river basin in ilam province, iran)

the runoff simulation in a watershed provides insight on the processes affecting runoff generation and the stream flow characteristics like spatial and temporal variability of stream flow. this insight helps managers and planners in informed decision-makings on water resources management and planning. the objective of this study is to compare the performances of the complex swat model and the simple ihacres model for simulating runoff in the doiraj river basin, ilam province. for this purpose, swat model due to having many parameters affecting stream flow and the use of gis, and ihacres model due to the low and easy access data requirements, are very practical. in this study, the data over a period from 1994 to 2004 and the statistical criteria of r2, br2, and ns were used to evaluate performances of ihacres and swat models. for ihacres model, values of r2, br2 and ns were estimated equal to 0.34, 0.112 and 0.33, respectively for calibration period and values of 0.47, 0.235 and 0.43, respectively for validation period. in addition, for swat model, the coefficients were estimated equal to 0.41, 0.314 and 0.12 respectively, for calibration period and values of 0.68, 0.632 and 0.56, respectively for validation period. final results of this study showed higher performance of swat model relative to ihacres model for simulating daily runoff in doiraj river basin and can be used to simulate runoff in the watersheds with limited data and similar natural conditions.