Document Type : Research Paper

Authors

• Behrouz Mohseni ¹
• Hadi Razzaghian ¹
• Abdollah Darzi-Naftchali ²
• Esmaeel Nikzad ³

¹ Scientific Board, Department of Natural Resources and Environmental Engineering, Payame Noor University, ‎Tehran, Iran

² Assistant Professor, Faculty of Agricultural Engineering, Sari Agriculture Sciences and Natural Resources University, ‎Iran

³ GIS Expert of Mazandaran Regional Water Company, Iran‎

Abstract

Runoff as one of the water balance components of a basin, is of great importance in watershed and water resources management. Suitable estimation of runoff is requires to determination of runoff coefficient. In this study, runoff coefficient was estimated for return periods of 25 and 50 years using rational, SCS and Cypress-Creek methods for basins up to 50 square kilometers. GIS software was used to overlay layers and basin analysis. Chow^, s table was used to correspondence different methods. Due to the lack of compliance with Chow^, s table and estimating lower runoff coefficients than reality in most of the study area, Rational Method did not provide suitable results. Cypress-Creek method was also effective in some basins due to it similarity with the SCS method. Average equivalent runoff coefficient of C₂₅=0.37 and C₅₀=0.41 demonstrated high accuracy of SCS method compared with two other methods. According to the soil conservation service method, minimum and maximum runoff coefficients of 25- year return period were related to Chalakrud 1 (0.06) and Safarood 4 (0.61) watersheds, respectively. Also, the minimum and maximum runoff coefficients of 50- year return were 0.1 (for Chalakrud 1) and 0.65 (for Safarood 4), respectively. According to the results of three methods, the lowest runoff coefficients were obtained for watersheds with the highest area and the lowest rainfall intensity.

Keywords

• Water Balance
• runoff
• GIS
• Resources Management
• watershed