Model experiments were and are still being used to verify some theories and some phenomena in groundwater system for the sake of covenience and thoretical rigorous analysis. The groundwater movement is so complex that the model experiments may be extremely useful. In the case of salt water intrusion, the model experiments are used especially. Present experiments were done by the equipments showing in Photo.1. The levels of fresh water and salt water were keeped constantly by two special vessels.
Results of experiments 1. By puming up at distance 50 cm from 0 cm (“ A” ) and elevation 26 cm (poit sink), intruded wedge of salt water retreated to disiance 22cm from (“ A” ). (See Photo.5, Exp.2) 2. By pumping up at distances 50 cm and 40 cm, and elevation 26 cm (point sink), intruded wedge of salt water retreated to 30 cm from 0 cm (“ A” ), and the interface coned up in all that zone. (See Pnoto.6, Exp.3) 3. By pumping up at distance 10 cm and elevation 26 cm (doint sink), intruded wedge retreated to 19 cm from (“ A” ) and coning up of the interface was a little. (See Photo.7, Exp.4) 4. By pumping at distance 20 cm and elevation 26 cm (point sink), intruded wedge retreated to 13 cm, but its retreat was not so much as compared with the case of Exp.4. (See Photo.8, Exp.5) 5. When the flow volune of fresh water increased to 16.2 cm /sec from 10.5 cm /sec, intruded wedge retreated to 22 cm from 0 cm (“ A” ). (See Photo.9, Exp.6) 6. When the flow volume of fresh water decreased to 3.4cm /sec from 10.5cm /sec, intruded wedge intruded more. (See Photo.10, Exp.7) 7. When point sink was inserted into the salt water (elevation 5 cm), intruded wedge retreated to adout position of point sink (distance 35 cm). (Photos.12,13,14, Exps.9-4,9-2,9-3)
Observations of above-mentioned experiments were doing in steady states except some cases.

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The chemical analysis has two practical purposes; one is the examinaton of water for drinking, agricultural and industrial uses the other is the interpretation of waterquality for fhe development and managenent of groundwater. Of the two the latter is needed to determine the major dissolved constituents in water.
Electrical conductivity, the reciprocal of specific resistance, has been used for estimating the concentration of total dissolved salts in water. In this paper the method of estimation is proposed taking consideration to the variations of concentration and composition in water samples. A first of “ diluted conductivity (DEC)” is obtained by the equation DEC. EC" in-which the electrical conductivity of water (EC) is expressed in micromhos/cm. The first estimate is then correlated with the concentration of total ions (T epm) by the following equation T. (DEC+ 25.3 Alk. )/111 in which Alk. is alkalinity of the sample expressed in epm. The ratios of estimated value from analytical one range from 91 to 109%, and the mean value and standard deviation of them is 100.55% and 3.77% respectively. Owing to the simplicity of conductity measurement, the method has many practical uses as follows; (1) checking of the correctness of analysis, (2) estimatien of the concentration of unknown ion or group of ions, from totol ions, (3) classification of hydrochemical facies.

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The investigated area is a small, talus deposit in the foot of Mt. Oasa. The investiga-tion of the mechanism of ground water in this area was carried out.
It was clarified that the ground water storage was active in this small talus deposit.
The concentration of tritium covered 10 to 155 TR.
The spring water in high elevation and the ground water in the deep layer showed_ the maximum value and minimum value respectively.
This fact indicates that the precipitation exuded comparatively fast in the spring_ water in high elevation.
A ground water. recession curve showed the variation of base flow with time during periods of little or no rainfall. This decrease is shown in approximating the formula. of Q = Q₀^-at.

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Water well has a large-diameter hole, and is protected by the thick steel casing for the sake of pumping-up of water.
The writer fited the probe of small density logging equipment in water wells, as shown in figure 1.
A water well in Sofue toun Aichi prefecture which has the already known data of normal resistivity and natural-gamma logs was tested with use of the improvemental density logging equipment to depth of 160 meters.
In consequence, the writer known that density logs was more efficiency for the geological identification in quaternary than normal resistivity and natural-gamma logs.

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