The sources of city water in Mitaka city, western part of Tokyo metropolis, is mainly the groundwater from about thirty artesian wells.
One of them, which is called No.4 (300 mili - meters in diameter and 200 meters in depth), is the multiaquifer well having five punping aquifers. The well was not suitable for city water for long time because the water was 0.2 ppm in manganese content. As another multiaquifer wells were in good quality, it was an important problem to find out manganese - rich aquifer of No.4 well.
In the process of hydrogeological investgations, two unique aquifer-test apperatuses were invented by Y. Otomo. Using the water-well flow meter the direction of water flow in the well was measured under static condition. Using the special water-sumpler the water of individual aquifer was sumpled under pumping condition.
As a result of the investgations, it had existance that uppermost aquifer is essentially rich in manganese and that under static condition the groundwater flows into from the aquifer to another aquifers.
Finally after sealing up the aquifer and pumping out of water for two years, the concentration of manganese ion became 0.02 ppm. Thus nowadays No.4 well is sufficiently used as the city-water well.

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The artificial recharge through artesian well is one of the direct method. The troubling problem in this method is clogging of the recharge well or adjacent aquifer materials.
Writers have experienced that clogging chiefly has been attributed to the different chemical characteristic of both the native ground water and the reharge water and air in the recharge water, through the testing work carried out by the group of investigation of the Geological Survey of Japan. The clogging because of them occured temporarily and its agent was adequately removed by intermittent pumping and recharging of the recharge well. But it would seem that the permanent decreasing of permeability of adjacent aquifer occurred as a result of the repeated pumping.
Therefore, the preliminary evaluation necessitates the consideration of adequacy of the recharge water to the native ground water.

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Using six years of data, the relationship between the depth of the river water and the water table depth of the shallow groundwater in paddy fields was studied and the following obtained;
1) The relationship between D (the depth of the water table of the shallow groundwater in paddy fields measured from the ground surface) and H (the water depth of the Aya River) could be expressed by a simple, linear equation as shown in Eq. (3).
2) The values of RDH show that the degree of the relationship between D and H varied with the values of Hg (the height of the well sites above sea level). A linear equation was constructed, as shown in Eq. (4), showing the relationship between RDH and Hg.
3) The degree of the relationship beween D and H also varied with L (the distance of the well from the Aya River). Eqs. (5) and (6) were constructed to show the relationship between RNDH and L. RNDH had the same value as RDH during the non-irrigation period.

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An unsteady state, two dimensional flow is simulated by the discrete analog model, that is R - C network composed of a series of resistors and capacitors. In this model, a given problem is solved on the nodes and lines of the grid expressing the actual field.
The simulation of this model is based on the analogy between the unsteady state ground water flow and kirchhoff's law of electric current. Considering the four scale factors, aquifer constants, boundary conditions and pumping conditions are converted to the values of resistors and capacitors, pulse width and pulse amplitude. Therefore, the aquifer constants and boundary conditions are most important factors of this model. After all, resistors are analogous reciprocally to the coefficients of transmissibility of the aquifer, and capacitors are analogous to the coefficients of storage. When the field boundary does not coincide with the lines of the network grid, the values of R- C circuit are calculated by vector - area technic.
The equipments for analysing R-C network analog model are formed of sawtooth generator, pulse generator, synchroscope, analog model and calibrate resistor. Analog model is constructed on an acrylic board. It is 3 mm thick, and is perforated in square grid with 2.5 cm intervals. Eyelets are inserted in the holes to make terminals. Resistors and capacitors are connected to the terminals by solder, and one side of the capacitors is connected to the earth.
Pulse generator produces rectangular pulse. It is send to the pumping well junction of the analog model. The sawtooth generator gives the excitation to the pulse generator to produce pulse. Pulse width is analogous to the pumping period and pulse amplitude is analogous to the pumping rate. The probe of the synchroscope is touched to the observation well junction of the analog model. Then, on the screen of synchroscope, the response wave is drawn in obedience to the distance between pumping well and observation well.
As the response wave is time-voltage curve, it is converted to time-drawdown curve by the four scale factors and the scale of the synchroscope.

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This paper describes a theoretical consideration about the effect of pumping of fresh water on the motion of seawater interface already formed in a confined aquifer. At first, the differential equation of interface is derived from the fundamental equation of confined water in the case where the aquifer is impervious at its lower surface and has the pumping well distributed continuously at its upper one, and is solved under the conditions that the constant supply of fresh water is given at a fixed point of the upper course and the pressure of water is taken as a hydrostatic distribution. From this solution, it is found that the toe of the interface is moved backward or forward by the inerease of fresh water inflow or of the amount of pumping, respectively and is also, moved more back according to the more concentration of pumping intensity on the lower course of aquiter. Finally, an example is shown for the method through which, in the coastal region where the residual flow of fresh water into the sea exists, this residue is fully pumped up within the limit that the present toe of interface remains immoved.

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[in Japanese]

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