Using Satellite Images and Srm Hydrological Model for Evaluating Runoff Resulting from Snowmelt in Navrood Basin

Original scientific paper Determining snowmelt runoff share of watershed basins with snow and wet snow regimes is one of the main concerns of the experts in water resources field, assessment of which has been done so far with difficulties and high rate of error due to lack of snow survey and weather stations in highlands of basin and use of traditional surveying methods. Lack of integrated management system in watershed basins, flood control, soil erosion, drought prediction and water supply are among problems the impacts of which, from a microclimatic perspective, can effectively be dealt with through modelling of snowfall surface features. In this research, satellite images of snow cover and temperature of MODIS sensor were received in a 9-year period as from Oct. 16 until Apr. 24 from 2000 to 2009; these images were processed in ERDAS Imagine software through codes provided by MATLAB software and then the data of snow cover and ground surface temperature were extracted, their graphs were drawn and the data changes regime in the related period was investigated. In the next stage, the data as well as the variables and the required parameters from the ground stations existing in the basin were entered into Snowmelt Runoff Modelling (SRM) hydrological model and the model was measured for the water year 2000 ÷ 2001. Data of satellite images were also received and processed by the model. The results showed a 12 percent share in snowmelt runoff as compared to the total volume of flow in this year and comparison of changes in snow cover surface area and surface temperature obtained from satellite data with the amount of water release confirms that snowmelt runoff has a noticeable role in Navrood water in such a way that with decrease of snow level and increase of snow temperature, the basin water release increases. Investigation of data related to discharge – snow cover surface, temperature – snow cover surface and temperature – discharge indicated that data affect each other. Increased snow cover surface corresponds with decreased discharge, increased snow cover surface corresponds with decreased temperature and in temperature – discharge diagram; increased temperature is directly related to increased discharge.