برآورد سطح پوشش و مقدار ريزش برف در ارتفاعات شمال تهران مطالعه موردي : حوضه رودخانه تجريش (دربند و گلابدره ))

Falling and Melting of Snow in the North Mountains of Tehran

In many areas snow is the dominant source of surface run off. Snow melting usually begins in the spring and if mixed with rainfall in warm season, cause overland flow. Therefore, information about the volume of the fall and melting of snow is very important to foresee the situation of the flow and its volume. Usually in equipped areas, the thickness of snow is measured through the use of standard snow boards and snow stakes; but in unequipped areas usually empirical methods are used for measurement of the thickness. The area under consideration is one of the unequipped areas; therefore empirical methods were used to estimate the cover and volume of snow in the area . The factors used in this investigation are temperature and rainfall data for various interval times belonging to 6 stations in and around the area with the length of 20 years data. The results show that the snowfall starts from October with the maximum falls in December and January. While temperature rises melting starts and in Jun there is no snow left in the area. The average of coefficient of snow in the area is from 92.5 percent in January to 0.9 percent in October.