Streamflow Estimation for UpstreamWatersheds of Boukan Reservoir Dam Using Precipitation and Temperature Climatic Variables

The hydrological variables estimation is very important for safety of hydraulic structures and facilities، surface water resources management and planning. The streamflow measurement as one of the important hydrological variables has various limitations. For this reason، application of the hydrological models with available and easily measured variables is the important and necessary approach. The aim of this research is the possibility of available climatic variables e. g. precipitation and temperature for seasonal and annual discharge estimation. Data of precipitation، temperature and discharge related to upstream watersheds of Boukan reservoir dam were used for 16 years period during 1993-2007 in this study. Multiple and stepwise regression models were determined in annual and seasonal scales for each watersheds using SPSS 17 software، then calibration and validation of each models were examined. Root mean squared error (RMSE)، relative error (RE) and efficiency coefficient (CE) were used for models evaluation. The results showed that the most models performance was very good and stepwise regression has more accurate results than multiple regression. Also، the RE، RMSE and CE range criteria were changed between 20. 96 to 44. 69 and 22. 80 to 81. 11 percent، 0. 37 to 7. 37 and 0. 05 to 7. 53 m3 s-1 and 0. 7 to 0. 94 and 0. 31 to 0. 92 for annual and seasonal scale، respectively. Ratio of precipitation influence on discharge was very low in summer in comparison to other seasons because annual model will not be accurate for estimating discharge in summer.