We have measured soil moisture content, ground water level, soil and atmospheric temperature, net radiation, and so on in sand dunes to get basic data for making an irrigation and drainage plan in sand dune areas. The place investigated is located in Hamaoka sand dunes in Shizuoka prefecture at a distance of about km from the seashore. This area has 1860 mm in annual rainfall, 0.1-0.5 mm in the size of particles, 1.4-1.5g/ cc in apparent specific gravity, 43-47% in porosity, 4 × 10^-2cm/ sec in saturated hydraulic conductivity, K_s, and capillary moisture distribution curve (C. M. D. C.), as shown in Fig. 2 from which we can get 7% in field capacity. Fig. 4, 5, 6, show net radiation, heat flux into the soil, soil and atmospheric temperature and humidity, from the results of measurement. Evaporation calculated by using these results is shown in Table 1, the mean evaporation is 2-3 mm/ day and showed 60% of net radiation. Fig. 7-10 show results of G. W. L. measurement, from which we can know that G. W. L. began to rise 2-3 hours after precipitation began, and its rise was 4-5 times as much as rainfall. In 23 mm rainfall it took two days to recover the former G. W. L. over a week in 123 mm rainfall. The gradient of G. W. L. is about 4/ 1000, as shown in Fig. 10. The moisture characteristics of the soil are shown in Table 2-5. When it rained we could see the constant moisture content along the direction of depth and a similar soil profile to C. M. D. C. when the infiltration front reached G. W. L., After the rain the variation of soil moisture content results in complex variations, in the process of drainage and evaporation, especially the movement of G. W. L. The drainage proceeds with the fall of G. W. L. Before falling, however, it was controlled by the rise of G. W. L. Evaporation calculated by the equation of water balance is nearly identical with that by heat balance. As mentioned above, the variation of G. W. L. has an important effect on the soil profile of this place investigated.

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To aquire reliable information of the drop size distribution of natural rainfall is of great importance to the soil erosion control of sloped farmland. But few investigators have treated erosion in relation to the size distribution of natural rainfall. This may come from the fact that the measurement of drop sizes in a natural rainfall composed of hundreds of drops has been an almost insuperable task.
Then, the authors constructed a Winn type raindropmeter (tentatively named) which gives an instant result of drop size distribution and tested it's performance Further, measurements and brief analysis were carried out on the drop size distribution of a natural rainfall. The results were summarized as follows:
(1) Two metal wires (φ 0.1 mm) were charged to +250 V to attain the maximum value of S-N ratio within the output voltage level to drive the counter.
(2) In order to set the reference voltage for arbitrary rainfall, the voltage of each channel was made movable.
(3) In calibration, it does not always necessarily follow that the falling velocity of the droplet reaches the terminal velocity. The falling height of the droplet, h= 50 cm is sufficient for calibration as illustrated in Fig. 4.
(4) Calibration curve is given in Fig. 5 and the relationship between output voltage (V) and drop radius (R) is approximately represented by V=CR^r, where C= 0.91 and r= 1.44.
(5) Natural rainfall was measured on Oct. 26, 1970 by the raindropmeter and the filter paper method. The results obtained by both methods coincided well with each other as shown in Fig. 6. So, this apparatus is useful for practical purposes.
(6) The drop size distributions measured by the apparatus during a light rain (Oct. 26, 1970) are illustrated in Fig. 7. The smaller the droplets are, the greater the numbers of droplets in a rainfall. Also heavy rainfall is always accompanied by numerous fine droplets.

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As a basic study on control of local meteorological condition by sprinkler sprays, the behavior of fine water droplets in the air was studied.
The data obtained are summarized as follows;
1) The equations of motion of flying water droplet in the moving air are as follows;
for X direction _??_
for Y direction _??_
for Z direction _??_
Drag coefficient can be expressed as follows;
R_e<2 _??_
2≤R_e≤100_??_
100≤R_e<1000_??_
R_e≥1000 C_D=0.45
Flying velocity and trajectory of a fine water droPlet can be theoretically calculated from the above equations and the numerical calculation method.
2) Water droPlets which satisfy the following relationship do not fall on the ground but drift in the air. These droplets play an important role on the control of local meteorological condition.
_??_
3) Calculated data shows that drifting droPlets have nearly the same flying velocity as wind. Therefore the aspect of diffusion and mixture of fine water droplets in the air is the same as the aspocts of flow of the atmosphere. Also, the change in diameter of drifting water droplet due to evaporation can be calculated by the following equation.
_??_

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Experimental studies were conducted to make clear the influence of continuous cropping and soil moisture on efficiency of water consumption in the rice field. The results are summarized as follows:
Continuous cropping and decrease in soil moisture level decreased not only the total dry matter of top and the fine grain yield of rice plant but the ratio of the fine grain yield to the total dry weight of top.
It was mode clear from an analysis of coefficients of increase in evapotranspiration ratio with increase in weight of total dry matter of top of rice plant that the influence of soil moisture level on efficiency of water consumption was much larger than that of plant luxuriance.
The efficiency of water consumption was greatly affected by continuous cropping. The efficiency of water consumption in the continuous cropping soil was smaller than that in the virgin soil, and the difference in the efficiency of both soils increased when the soil moisture level is high.
Furthermore, the efficiency of water consumption decreased with decrease in soil moisture level and with increase in the duration of insufficient period of soil moisture. Similarly, the efficiency of water consumption became lower the longer the period of cultivation.

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Merits and demerits of division and combination of water distribution systems from the stanpoint of the energy are discussed on the basis of the previous paper by setting up a model water distribution system. The facts generalized from the results are as follows.
Combination of the systems is an effective means for reducing friction loss, which is one of the energy components for water distribution and which is decided mainly from the shape of the object region, and the division of the system supported with booster pump or pressure control valve is the other means for reducing the pressure regulation loss which is decided from the topographical character (shape and undulation). Then the significance from the energy viewpoint of division and combination of the water distribution systems becomes clear by analyzing the energy for water distribution into components, and these analyzed energy components are important indexes when the objective region is divided into the parts.

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Agricultural pipe lines have been used for the effective utilization of water resources, the introduction of large agricultural machinery and for other purposes.
Waterhammer is one of the greatest problems of hydraulic flow in pipe lines.
From the stand point of analytical methods concerning the natural flow system of waterhammer, there are the following:
1. Algebraic analysis (not including the nonlinear friction term).
2. The graphical method (not including the nonlinear friction term).
3. The direct analytical method of the basic partial differential equation (including the nonlinear friction term).
Reducing the velocity of the pressure wave is one way of controlling the waterhammer.
If water flowing in the pipe line contains nondissolved air, pseudo velocity of the pressure wave is greatly reduced.
In this paper, we have made the assumption that air and water are a homogeneous mixture. Under this assumption, we calculated the mean dencity, modulus of elasticity, etc.
Using the above values, we solved the basic partial differential equation of waterhammer with the aid of a digital computer. Other studies were made experimentaly, using a simple pipe, as shown in Fig. 1.
Compare with the theoretical and experimental results, shown in Fig. 7, and Fig. 8.

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To promote the salinity change in freshenning reservoirs of the standerd type, the flushing effects of the outlet gate and syphon pipe which are set at a deep part of the lake are theoretically treated. Using the theory, the processes of salinity change in the freshenned layer, of changes occur in the fresh water volume and salt water, water surface and salt spring layer, the drained discharge from the outlet gate and syphon pipe can be analytically simulated.
The theory is scheduled to be checked by the experimental results of the freshenning process on Imariwan bay and Yokakuwan bay.

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Digital computer simulations for the freshenning process of a lake which has an outlet gate and a pipe for the selective drainage of lower salt water are applied to the two analysises of Imariwan bay and Yokakuwan bay. The simulation of the freshenning process of one day intervals gives good information for rational management of lakes.
We made the mathematical models of the freshenning process for two lakes by using a new theory which has been deduced in the preceding paper. These mathematical models were checked by the results of hydraulic model tests which were performed on the Imariwan bay and Yokakuwan bay.

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The experiment was performed when the sill was placed in the wide end of the stilling basin of the water-cuschion-type's drop. Further, this study was performed with the object of creating a perfect overflow for the small-scale drop.
The author changed the length and depth of the stilling basin and the slope of the bottom at the downstream, and looked into the condition of the flow. As a result of this, when l was approximately equal to X, a lot of the running water was forced to change direction to the drop wall side by the sill and the marked dissipation of the energy in the downward pool of the nappe was advanced. Only, l is the length of the stilling basin and X is the horizontal distance of the point from the crest of the drop, at which an extension line of the over-nappe at the beginning of the interpenetration into the stilling basin crosses the bottom of the stilling basin. He indicated that a drop of this type discharged high functions for the dissipator of the energy, and mentioned the practicality.
When the still was suitably placed, the length of the stilling basin of the drop was reduced to 40% or 50% of the length of the stilling basin for the water-cuschion-type's drop.

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During storage, after the soil has been remolded or compacted, the structure of the cohesive soil undergoes a change and, as a result, the pore pressure and shearing properties also do a change. In this paper, the effect of storage on pore pressure and shearing properties of the compactedsoils wet of optimnm moisture content in shown.
When a confining pressure of 1.0kg/cm² was applied to a compacted soil, the pore pressure in the soil increased for thirty to a hundred minutes and then dropped for about ten days. The greater part of the drop of pore pessure occured in the first day of storage.
The effect of the storage on the shearing properties was detected mainly in the behaviour of pore pressure. The amount of increment of pore pressure during a shear test showed a tendency to increase but pore pressure itself had low value as the longer the storage was. The effect of the storage did not appear on the shear strength.
The condition of storage also had an influence on the shearing properties of compacted soil. The samples stored under a confining pressure of 1.0kg/cm² and then subjected to a triaxial compression test had greater strength than the sample stored under zero kg/cm2 and than subjected to a triaxial test under a confining pressure of 1.0kg/cm².

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