Snowmelt-runoff estimation using radiation SRM model in Taleghan watershed

Snowmelt runoff has a considerable role in water supply in mountainous watershed areas. This study was used to estimate snowmelt runoff by using snowmelt runoff modeling (SRM) in Taleghan watershed, Iran. The SRM is a hydrological model that has been used to estimate daily flow in mountainous watershed areas. This model computes the snowmelt runoff by using meteorological, hydrological parameters and physical characteristics of the basin, and in addition, shows the results as graphs and numerically accompanied with observed amount of runoff. The purpose of this study is to evaluate the degree-day and radiation of the SRM and to also offer the appropriate method for temperature interpolation, which is the principle input of the SRM. Values of these input parameters were defined and model simulation was carried out. The computed and observed hydrographs were plotted. Hydrographs were compared to each other by using visual inspection, the efficiency coefficient of Nash-Sutcliffe (NSE) and difference of volume percent (D-v). The NSE value in the validation period was estimated from 0.65 to 0.86 and 0.80 to 0.88 for degree-day and radiation models, respectively. The D-v in the validation period was estimated from 1.85 to 18.36 for degree-day model and -0.65 to -4.54 for radiation model. Seven different temperature interpolation methods were performed using degree-day and radiation models of SRM over the Taleghan basin. Results showed that estimation of temperature by different methods can cause differences between estimated and observed runoffs. Also in order to overcome the shortage of measured data in the snowmelt runoff modeling, the temperature interpolation method and adding the radiation factor to the model would greatly help in improving the simulation accuracy and describing the snow-hydrological behaviors in watershed area.