ON THE SNOW COVER AND SNOW-MELTING RUNOFF IN THE TAKINAMI RIVER BASIN, CENTRAL JAPAN

Autor: Tadashi Arai, Toshie Nishizawa, Kazuo Kotoda
Rok vydání: 1967
Předmět:
Zdroj: Geographical Review of Japan. 40:426-444
ISSN: 2185-1719
0016-7444
Popis: In the winter season of 1963, snowy regions of Japan were attacked by the phenomenally heavy snow-fall which caused many kinds of disasters in these regions. This investigation was made as a part of synthetic surveys on the disasters caused by the heavy snow-fall. The Takinami River is a branch of the Kuzuryu River, and its drainage area is about 68km2. The highest mountain in the basin is about 1700m above sea level. Climatic data on accumulation and melting of the deposited snow were taken at several observation stations in the river basin as shown in Fig. 2. In 1963, total water equivalent of snow cover in the river basin was obtained from the result of the snow survey which was made along six snow courses. Total water equivalent for 1964 was obtained by use of aerial photographs which had been prepared by the Geographical Survey. Amount of snow-fall in 1964 was exceptionally small comparing with the preceding years. Total water equivalent in March of 1964 was about 4937×104m3, while the amount for March of 1963 was about 9606×104m3. For the calculations of the above values, density of deposited snow-cover was assumed to be 0.52 for 1963 and 0.50 for 1964. Micro and local climatic observations on the ablation of snow cover was also made at several stations in the river basin, aiming to find out the main factors which contributed on the ablation process. To measure daily total amount of ablation, the ablation bucket was adopted which was made of hard plastic sheet painted in white. Heat balance at the snow surface was measured at Kinehashi including the following items: _??_Incoming and reflected short wave solar radiation, Temperature and humidity of air and wind velocity over snow surface, Temperature and density of the deposited snow cover. Albedo on the snow surface decreases with the increase in the density of the snow cover and it finally reaches 0.5 or 0.4 in several days after the deposition of new snow-fall. Total heat supply on snow surface in the ablation season was calculated by the following equation, Rn+h(θa-θs)+1.5h(ea-es)=80M h=c•ρCD•u=1.67u×10-4(ly/s•°c) where Rn is net-radiation on snow surface, h is heat transfer coefficient, M is water equivalent of melted snow and U is wind velocity over snow surface. From the result of the above calculation, it was found that the incoming short wave radiation occupied a great portion of the heat supply on the surface of deposited snow. The amount of ablation obtained by the ablation bucket and that obained by the heat balance calculation is compared in Fig. 7. Result of the ablation bucket is also compared with the depression of the depth of deposited snow as a measure of the representativeness of the bucket. Evaluation on the amount of snow-melting runoff from a river basin have been made by basing on degree day factor or ablation factor, but these studies did not analyze the fundamental characteristics of the runff. As it was considered that physical and chemical properties of river water might indicate the route where the water had passed, so water temperature was measured continuously during winter of 1964. Discharge was measured at the intake dam of the Yakushi Power Station by use of recording gauge. Strong insolation is usually observed on the days when anticyclone covers the region, and an example of such a weather condition is shown in Fig. 14. In Fig. 11 and 12, amount of daily total discharge (or discharge at 09h) and daily mean air temperature are shown to indicate the relation between runoff and air temperature.
Databáze: OpenAIRE
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