Both mixing processes in a fresh-water lake and residence time of groundwater in its drainage basin have been made clear by using environmental tritium as a tracer on Lake Chuzenji. The lake covers an area of 11.97 km² at an altitude of 1, 269m, having a large drainage basin of about 119.68 km². The mean depth is 95m and the maximum 172m.
A field survey was carried out from July 29 to August 3, 1978. Water samples for tritium analysis were collected at eleven stations, as shown in Figure 1. The sampling of lake water was made every 20m vertically. Temperature, ply, and electrical conductivity of the water were determined on the spot. The values obtained are indicated in Figure 2. Tritium concen-trations of lake water are shown in Figure 3 and those of stream water and groundwater in Figure 4. The mean tritium concentration of lake water was 34.7 TU, and a significant variation was not found throughout the all vertical profiles of the stations. Concerning the vertical profiles of tritium concentration in lake water, the lake water would be well mixed at least vertically. The tritium concentration of Shirakumo Falls, 37.8TU, showed nearly the same value to the lake, which shows that the Falls would be poured out as the seepage of the lake. Spring water from elevator shaft, which was drilled near Kegon Falls for the sight-seeing of the Falls, showed 33.3 TU. This figure was also the same as that of the lake. Those of spring water in Jigoku-zawa and of the well near the lake shore were 21.5 and 26.9 TU, respectively, showing lower than the lake water. This fact seems to reflect the influence of recent precipitation. Yukawa River, 37.9 TU, showed higher tritium concentration than both precipitation and the stream water flowing into Senjuga-hama.
The annual water balance of the lake was calculated in the period from 1952 to 1977 (Table 3). Meteorological data at the Chugushi Meteorological Station were used as basic data in the calculation, and evapotranspiration from the drainage basin and evaporation from the lake were calculated by Penman's method. The tritium concentrations of precipitation in Tokyo and Tsukuba from 1952 to 1977 were used to estimate the mean tritium concen-tration of the lake water. The calculation was carried out on the assumption that lake water is completely mixed every year.
As a result, the following conclusions were obtained.
1. The mean inflow to the lake is about 1.92×10⁸m³•yr^-1, that is, 6.09m³•sec^-1, and the mean residence time of the lake water is determined to be about 5.9 years. In spite of the huge volume of lake water, the mean residence time is shorter than expected, because the area of drainage basin is about ten times as large as that of the lake.
2. The discharge from the lake depends upon groundwater outflow which is about 4.76m³•sec^-1 and 79% of the total outflow. The propotions of evaporation and surface outflow are about 4% and 17%, respectively.
3. The vertical profile of tritium concentration in lake water and the result of the simula-tion of tritium balance support that the lake water would be well mixed in a year.
4. As a component of precipitation on the drainage basin, groundwater flow into the lake takes an average time of less than 4 years.

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In the central part of the Kanto plain, alluvial lowlands develop along the Tone, the Arakawa and the Watarase rivers. The alluvial lowland of River Tone is divided into Menuma, Kazo and Nakagawa lowlands. In the Kazo lowland and the northern part of the Naka gawa lowland, (1) microrelief of the flood plain, (2) stratigraphy of the Recent formation and (3) buried topographies were investigated. On the basis of the investigation results, the geomorphic development of the alluvial lowlands was discussed in relation to buried topo- graphies under the Recent formation (the “pre-landforms” of the alluvial lowlands).
In the northern part of the Nakagawa lowland, the deposition of the Recent formation was taken place in a wide and deep valley, which is called the “Nakagawa buried valley”. This valley was formed by River Watarase at the maximum of the Lastglacial period (before at least about 18, 000 y. B. P. in ¹⁴C age). The Postglacial transgression reached to the inner part of this valley at about 4, 000 y. B. P. in ¹⁴C age. Marine deposits are found at almost all the locations in the Nakagawa lowland. After about 3, 000 y. B. P. in ¹⁴C age, additionally to River Watarase, River Tone and a distributary of River Arakawa flowed down in this wide and gentle valley floor, and deposited thick (more than lOm) fluviatile deposits. The natu-ral levees in this lowland developed along the many former river courses with free meander-ing.
In the Kazo lowland, Obaradai - Musashino (late Pleistocene) terraces exsist which are thinly covered with the Recent formation. These Pleistocene terraces were dissected by narrow valleys (called the “Kazo buried valleys”) at Tachikawa period (latest Pleistocene). At the maximum of the Lastglacial period, no big rivers dissected the Pleistocene terraces in this area and the Pleistocene terraces with only narrow valleys remained. At maximum of the Postglacial transgression, the marine area extended only to the narrow valleys which dissected the Pleistocene terraces. After the period of peat deposition (about 4, 0003, 000 y. B. P.), River Tone and a distributary of River Arakawa began to flow in the Kazo buried valleys. At the early stage of the fluviatile deposition, the sedimentation occurred only in the narrow valleys and the Pleistocene terraces still remained widly in this area. When the narrow valleys were filled up, sedimentary area of fluviatile deposits spread over on the Pleistocene terraces. Due to (1) the extention of this sedimentary area and (2) the subsidence continued since late Pleistocene in this area, the Pleistocene terraces were rapidly covered with the alluvium. As a result, this neighboring area was changed into an “alluvial lowland” (the Kazo lowland). In this lowland, the thickness of the Recent formation is very thin (less than 5m). The river courses are located almost above the Kazo buried valleys, so that the width of each meander belt or that of the natural levee becomes narrower than that in the Nakagawa lowland. Many slightly high mounds of the Pleistocene terraces thinly covered with the fluviatile deposits are found on the present flood plain.
It is concluded that the “pre-landform” of the alluvial lowland is one of the important factors which affect the depositional processes of each alluvium and the microrelief of the present flood plain.

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One of difficulties to evaluate previous researches on cognitive distance is due to a number of methodological differences which preclude the direct comparison of results: the kind of distance requested to estimate, the method of distance estimation, and the character of subjects varied from study to study. The aim of this paper is therefore to clarify the essential pro-perties of cognitive distance within a city, which can be found beyond the methodological differences. For that aim the author tried to analyze the cognitive distances in Nagoya city from as different viewpoints as possible.
The design of the investigation is following: (1) The origins of distance estimation were three senior high schools in Nagoya city, and the subjects were both the residents near each school and the students attending the each school. So the subjects can be separated into six groups (Fig. l and Table 1). (2) The destinations for distance estimation were twelve transporta-tional nodes, which were perceived well by the subjects and were distributed throughout Nagoya city (Table 2). (3) The subjects were asked to estimate both ‘crow-flight’ distance and time distance. The estimation of ‘crow-flight’ distance was obtained by the method of ratio estimation (Briggs, 1973; Lowrey, 1973), while time distance was estimated in terms of the method of magnitude estimation (See Appendix).
The results are summarized as follows:
1. Both the linear and power functions are fitted to the data well across all subject groups (Tables 3, and 4). This indicates that a high correlation exsists between objective distance and cognitive distance independent of distances used to estimate.
2. In most of results, parameter b in power function has been observed to be less than one. This indicates that the cognitive distance increases at a decreasing rate relative to objective distance (MacEachren, 1980). It was, however, supported only in the ‘crow-flight’ distance estimation in this study.
3. The nearer to the city center the origins are located, the more highly the cognitive 'crow-flight' distances are correlated with the objective 'crow-flight' distances. In the time distance estimation, the correlation coefficients were independent of the location of origin.
4. The 'crow-flight' distance estimation was affected by route distance (Table 6). This ex-plains that 'crow-flight' distance was over-estimated on the whole as route distance is neces-sarily longer than 'crow-flight' distance.
5. Time distance was estimated more correctly than 'crow-flight' distance (Figs. 2 and 3) and the 'crow-flight' distance estimation was affected by time distance (Table 6). It is sug-gested from the above findings that people cognize the distance within a city by means of time distance.
6. The subjects underestimated distances towards the city center compared with distances away from the downtown. This correspnods to the finding by Lee (1970). This tendency was remarkable in the 'crow-flight' distance estimation (Table 7).
7. There is no significant difference between the citizen group and the student group located at the same origin. And there also appeared to be no relation between the distance estimation and the other subject-centered factors such as age, sex, length of residence, driving status and travel mode.
It was thus clarified that stimulus-centered factors (Briggs, 1976) had greater influences on cognitive distance rather than subject-centered factors. Stimulus-centered factors are closely related with the urban structure in Nagoya city which has only one dominant city center and the radial railway pattern.

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The research on the three-dimensional behavior of subsurface water during and after a rainstorm throughout a small forested basin (0.56 ha) was carried out in the Tama Hills. The basin is located in the northeastern part of Kanagawa Prefecture, Japan and composed of flat valley bottom (mean gradient of 10°) and steep side slopes (mean gradient of 25°).
Twenty four borings were practiced to know soil profiles and depths to the Tertiary bed rock (mudstone) from the ground surface. As the results, soil profiles were classified as A-horizon, B-horizon, transported soil layer, weathered zone of bed rock and bed rock. Depths to the bed rock were about 3 to 4m in the valley bottom and 1.5 to 2m in the middle parts of the side slopes. The ancient V-shaped valley on the bed rock and its weathered zone were buried by the transported soil, and the present geomorphic feature was formed over. The transported soil is composed of loam and masses of weathered bed rock and assumed to be carried from upper parts of the side slopes. Fifty-six observation wells, being classified into Wells D and Wells S, were installed through-out the basin. The Wells D were dug to the top of the bed rock and used to observe the behavior of the “deep groundwater body”. On the other hand, the Wells S were dug to about 1m below the ground surface and used to observe the behavior of the “shallow ground-water body”. In order to characterize vertical distributions of soil-water pressure head in response to rainstorms, forty tensiometers were equipped at five sites. Three rainstorms with a total rainfall of more than 100mm occurred during an observation period from September 28 to October 21, 1979.
The major results clarified by this research are as follows:
1. The impermeable layer, the top of which is generally about 1m below the ground surface, is found almost over the basin. This layer plays important roles in building up the temporal shallow groundwater body and confining the deep groundwater body during and shortly after the rainstorms.
2. The impermeable layer is not found both in a lower part of the valley bottom and in vicinity of the ridge top. A lack of the impermeable layer in vicinity of the ridge top may affect the behavior of the deep groundwater body during the rainstorms. The rainwater brought on this part is expected to cause a quick response of the piezometric surface of the deep groundwater body to the rainstorms and make the piezometric surface rise about 10cm above the ground surface in some wells.
3. A temporal saturated zone is formed in the A-horizon during and shortly after the rainstorms and discharges into the stream channels, making an important contribution to stormflow generation.
There is a strong possibility of application of the results to other headwater basins in the Tama Hills, and therefore more similar researches must be carried out from viewpoints of disaster prevention and geomorphological evolution.

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