To develop a suitable water collection method for short-term hydrological process observation, the new water sampler, using automatic water sampler and modified plastic bucket with clock timer and electro magnetic valve, was developed. The actual application of this sampler in a study area shows that this system is applicable for the rainwater sampling for the throughfall intensity over 0.7 mm⁄h. The comparison result between isotopic content of hourly samples collected by this sampler and that of conventional bulk samples for selected four representative rainfall events shows that the weighted mean value of hydrogen and oxygen isotopic content in throughfall samples by this method showed almost same content as that in bulk throughfall samples. In addition, the isotopic content of the bulk throughfall samples in the δ-diagram was plotted on the regression line given by isotopic content of hourly throughfall samples of the specific rainfall event. This means that the precise time resolution samples collected by this new method represent time variation of isotopic content in the throughfall of the study area.
In this paper, the authors consider the relationship between surface water temperature in a basin of managed aquifer recharge (MAR) and the groundwater temperature in the case of the Rokugo alluvial fan, in northern Japan. The results show water temperature of basin No.2, installed in the center of the fan, has an influence on the shallow groundwater temperature at the observation well which is next to the basin. Under the condition of about 60L⁄sec water supply to basin No.2, water temperature inside basin No.2 does not have an influence on groundwater temperature at the Nonaka piezometer at depths of 20m and 50m which is 274m away from the center of the basin. This study is continued more in future, while increasing water supplies to the basin.