Impact of modified satellite products on snow covered area and modeling the seasonal snow potential in the Upper Euphrates basin, Turkey

Snowmelt runoff in the mountainous eastern part of Turkey is of great importance as it constitutes nearly 2/3 in volume of the total yearly runoff during spring and early summer months. Therefore, determining the amount and timing of snowmelt runoff especially in the Euphrates Basin, where large dams are located, is an important task in order to use the water resources of the country in an optimum manner.In this study, Karasu River in the Upper Euphrates Basin (10,275 km2) which is one of the main branches feeding the Keban Dam Reservoir is selected as the application area. For the hydrologic modeling studies conducted in the basin, snow covered areas are determined using MODIS optical satellite images. But optical satellites are hindered by cloud cover where at times when cloud is present, land cover can not be determined. For this reason, during winter (ablation period) and spring (melting period) it is crucial to determine snow covered areas with little or no cloud. In the study, daily MODIS satellite images on Terra and Aqua platfom are combined and modified in order to decrease the cloud cover. Modified satellite images are firstly compared with ground station data for validation purposes and later used to generate basin snow depletion curves for 2008, 2009 and 2010 water years. In the end, it is seen that modifying the satellite products has a significantly positive impact on snow covered area in the basin by decreasing cloud effect.The well-known conceptual hydrologic model, HBV, is applied to the headwaters of Euphrates River for 2008, 2009 and 2010 water years. Model parameters are calibrated using discharge values and later snow covered area output of model are compared with the modified snow covered areas. Taking into account the geopolitical position of Turkey in terms of water resources in the Middle East, hydrologic modeling studies give promising results indicating the possible operational use of runoff forecasting which can be an important desicion support tool for reservoir and basin management.