Abstract
Snow, as one form of precipitation, plays a very significant role in the water cycle and in water resource management. However, the spatial and temporal variations in snow cover complicate the monitoring of this role. Field measurements, especially in mountainous areas, are often impossible without the use of new technologies. In this study, moderate resolution imaging spectroradiometer (MODIS) at 500-m resolution has been used to provide a map of snow cover area (SCA) using the normalized difference snow index in the central Zab basin in West Azerbaijan, Iran. Eight-day composite data are used to minimize the effect of cloud cover and maximize the amount of useable SCA images. The importance of snow in this basin was simulated using a snowmelt runoff model (SRM) as one of the major applications of daily MODIS-8 images based on various algorithms. The location of snow gauge stations on digital elevation model (DEM) of central Zab basin extracted from advanced space borne thermal emission and reflection radiometer images by using bilinear interpolation method. The SCA index, along with spectral threshold on bands 2 and 4, provided a stable relationship for extraction of the snow cover map in the study area. The simulated flow in the water year 2010 to 2011 had a coefficient of determination (R2) of 0.8953 and a volume difference (Dv) of 0.1498%, which shows a good correlation between the measured and computed runoff by using the SRM in the central Zab basin. The first results of the modeling process show that MODIS snow covered area product can be used for simulation and measuring value of snowmelt runoff in central Zab basin. The studies found that the SCA results were more reliable in the study area.
Highlights
Iran is a low-water country located in an arid and semiarid region of the Earth
The purposes of this research are: (a) to investigate the capability of moderate resolution imaging spectroradiometer (MODIS)-8 daily images at 500-m resolution to provide the map of SCA32 and recognize changes in snow cover using the normalized difference snow index (NDSI); (b) to compare snow cover maps extracted from MODIS with the ground-based snow courses at some selected points in the central Zab basin to yield snow water equivalent (SWE); (c) to perform an snow cover area (SCA) validation using the MODIS products during the water year 2010 to 2011 for accumulation and ablation periods; and (d) to use the snowmelt runoff model (SRM) model to model the snowmelt runoff in the study area
These results suggest that the SRM can successfully simulate both diurnal water discharge and SWEs in the mountainous study area
Summary
Iran is a low-water country located in an arid and semiarid region of the Earth. snowfall is considered as the most important factor affecting water supply, especially in the summer, and snowfall is one of the important factors that controls the hydro-climate of the geographical area. The estimation of snow cover surface significantly improves the process of calculation and application of snowmelt models using remote sensing images.[5,6,7]. The purposes of this research are: (a) to investigate the capability of MODIS-8 daily images at 500-m resolution to provide the map of SCA32 and recognize changes in snow cover using the normalized difference snow index (NDSI); (b) to compare snow cover maps extracted from MODIS with the ground-based snow courses at some selected points in the central Zab basin to yield snow water equivalent (SWE); (c) to perform an SCA validation using the MODIS products during the water year 2010 to 2011 for accumulation and ablation periods; and (d) to use the SRM model to model the snowmelt runoff in the study area
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