新庄盆地の地下水観測資料(II) : 浅層地下水の水位・水温変化(1976〜1980)

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The data included in this paper concerns the continuous changes of groundwater level and groundwater temperature in the Shinjo Basin which is situated in the northern part of Yamagata Prefecture, Japan (Fig.1). Water levels and temperatures observed from 1970 to 1975 at four wells were reported in the previous paper (Higashiura and Abe, 1979). These data were continually recorded by self-recording gauges. No data of the well No.3 were collected because its observation was ceased, but the number is kept in the paper for the easiness of comparing with the previous paper. The position and the structure of each well are shown in Fig.2, Fig.3 and Table 2. All the data of groundwater level and water temperature at the bottom of wells are included in Figs.4〜18 and Table 3. Observation well No.1 (Photos 1 and 2) is located at the premises of the Sinjo Branch, National Research Center for Disaster Prevention (127m M.S.L., 38°41′17″N, 140°18′59″E). This well with a diameter of 2m is 7.5m in depth. Its geologic profile is as follows : about 30 cm dark brown humic soil, about 40 cm brown loam with pebbles and gravel bed in descending order. The annual change of groundwater level is about 2〜7.5m in a year. The highest level in these periods was 2.01m on April 7 th in 1980 and the lowest level was 5.88m on August 4 th in 1978. The lowest water level depends on the meteorological conditions of the year. The annual change of water temperature is as wide as 7〜8℃. The water temperature shows the lowest in April or May and the highest in September or October. In these periods the highest water temperature of 16.1℃ was observed on October 2nd in 1980 and the lowest temperature of 7.2℃ appeared on April 14th and May 12th and 19th in 1980. Observation well No.2 (Photos 3 and 4) is an abandoned one, formerly for domestic use. The annual change of groundwater level indicates tendency toward high in winter and low in summer. The change of water level is about 2〜3 m in a year. The highest level in these periods was 0.52m on August 10th in 1976 and August 28th in 1980 due to the infiltration of heavy rainfall. The lowest level of 2.83m appeared on February 28th in 1980, when the land was covered with thick snow. In regard to the annual change of water temperature the lowest temperature generally appears in April and the highest in October. The abnormal high temperature of 21.9℃ was appeared on August 18th in 1978 after a heavy rainfall and the lowest temperature was 1.4℃ on March 30th in 1980. The irregular change of water temperature during the winter of 1976 to 1977 is due to the snow because this station has no shelter except a wooden box. Everytime the water level is measured the recording chart is renewed in the snowy season, and the snow cover over the well must be removed. Though the removal work was carefully made, some snow blocks fell down into the well water and lowered the water temperature. Observation well No.4 (Photos 5 and 6) is also an abandoned one which used to supply water for an office. The annual change of groundwater level is about 2.5〜3.5m and the depression of water level in winter is remarkable due to the pumpage for snow melting in the built-up area. The highest level in these periods was 1.06m on September 18th in 1978. The lowest was 4.67m on February 16th in 1978. The annual change of water temperature is about 9〜16℃. An abnormally high temperature of 18.1℃ was observed on August 18th in 1978 after a heavy rain and the lowest temperature was 9.0℃ on April 22nd in 1977.
独立行政法人防災科学技術研究所の論文
1982-06-26

著者

東浦将夫
国立防災科学技術センター新庄支所

新庄盆地の地下水観測資料(II) : 浅層地下水の水位・水温変化(1976〜1980)

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