When the soil temperature is under the dew point of air, water vapour in the air will condensate to the soil. When there is a temperature gradient in the soil, water vapour in pores will move in the direction from high to low temperature. To investigate these phenomena experimentally, sand of the Hamaoka Sand Dunes was packed in a column, cooled from the bottom and exposed to moist air. Cumulative condensation and distribution of water content, tracer (Na Cl) and temperature in the sand were measured for analysis. The theoretical value of the amount of water vapour movement in the sand was calculated by the equations of Penman and Philip & de Vries.
It became clear that when the water content of the sand surface is relatively high, the water vapour in the air condensates on the sand surface, and when the water content of the sand surface is relatively low, the water vapour infiltrates the sand pores in vapour state and condensates to the deep layer. The amount of infiltrated water vapour agreed with the calculations by Penman's equation. It also became clear that when the water content is relatively low, the amount of vapour movement in the sand under a temperature gradient agrees with the calculations by Penman's equation, and when the water content is relatively high, it agrees with the calculations by Philip & de Vries' equation.

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The authors studied the relationship between physical properties and organic matter content of soil by comparing the properties of natural soils with those of soils from which the organic matter was removed by hydrogen peroxide.
Six different soil samples from Hokkaido (Table 1) were used, with a range in organic matter from 10 to 29%(Table 2). Also samples from six different depths of Nissha soil (Table 4) were used, with organic matter from 4 to 29%(Table 5).
The results obtained are summarized as follows:
1) Specific gravity of the soils decreases with increasing organic content (Fig. 2 ). The increase in specific gravity on removing organic matter increases with organic content of the soils (Fig. 3 ).
2) The specific gravity of the organic matter decreases with increasing organic content (Fig. 4 ).
3) Liquid limit of soils increases with organic content (Figs. 5 and 13). This is explained by the large specific surface of organic matter. The decrease in liquid limit on air-drying increases with organic content (Fig. 6 ). There is a large change in properties of organic matter on drying.
4) The decrease in liquid limit on removing organic matter increases with increasing organic content of the soils. The difference for fresh soils is larger than for air-dried soils (Fig. 7).
5) The effect of drying on liquid limit occurs at a higher water content for organic matter than for the inorganic part of the soil (Fig. 8).
6) Cation exchange capacity of the soils increases with increasing organic matter content of the soils (Figs. 10 and 14). Liquid limit increases with increasing cation exchange capacity (Figs. 11 and 15). Soils having higher values of liquid limit also have higher values of heat of wetting (Fig. 16).
7) Moisture retention for soils high in organic matter is large (Table 6, Fig. 18), and there is a large decrease in moisture retention after air-drying (Figs. 19 and 21).

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In a rotational field in sloping paddy field areas, it is one of the important problems to prevent the rise of the groundwater table due to the seepage from the surrounding paddy fields. In this paper, we considered the groundwater table in the field where two drain pipes were buried and discussed on the underdrainage problems in such a rotational field.
In the, theoretical analysis, the groundwater table was transformed into a straight line using the Zhu kovsky's function as shown in Fig. 1, then the flow problem was analyzed to obtain an equation of gro undwater table by the same procedure as in a previous paper of this series.
Next, the results calculated by the theoretical equation were compared with the observed data at the. Hiruzen test field in Okayama Prefecture, and it was found that the results are in a good agreement with each other as shown in Fig. 2.
At the same time, Fig. 2 shows that the groundwater table is affected by the depth of the impervious boundary, namely, it falls deeper as the impervious boundary becomes shallower. However, the effect is not so large that, even though a calculation is performed on the assumption that the impervious boundary is infinitely deep, the calculation will be applicable for practical purposes.
From Fig. 5, it is evident that the groundwater table is much affected by the gradient of slope. In the sloping areas where the gradient is steeper than 1/20, the groundwater table could be lowered sufficiently deep by only one drain pipe buried along the toe of the levee of upper paddy field. In the areas with a gradient from 1/20 to 1/60, two drain pipes are necessary to lower the groundwater table to the de pth of 0.5 m from the soil surface. Table 1 shows examples of the drain spacing when two drain pipes are used. These drain spacings are almost consistent with the standard values of a sloping paddy field, in which the seepage from under layers is predominant.

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This study aims at to clarify the method for determining reasonable spacing and riser height of a sprinkler used for protection and prevention agaist noxious insects.
In the 1st report, experimental discussion was made on the trajectory of droplets emittad from a sprinkler and the rate of application on the droplet recieving plane, as well as the distribution characteristic of kinetic energy of the droplets. The results obtained are summarized as follows.
(1) The maximum trajectory distance is shorter when the surface tension of liquid is less. Thereby, the uniformity of the rate of application of liquid on a plane is scarcely affected, but the uniformity of kinetic energy of the primary droplets is lowered. Therefore, it can be said that, in case the extermination of insects is taken as the subject, the use of a surfactant is not preferable.
(2) In case of evaluating the uniformity on a plane by the rate of sprinkling such as supplying water moisture, it is possible to make the sprinkler spacing longer than the maximum trajectory distance. However, in such a case that the uniformity is evaluated by the energy amount of primary droplets, it is necessary to make the sprinkler spacing less than the maximum trajectory distance. When the extermination of insects is the subject, importance should be attached to the latter.
(3) The trajectory distance of droplets is different according to when the sprinkler is rotated or not. However, the influence of component velocity along the rotation direction of sprinkler is only slight instead the influence of air stream caused by droplets emitted from the sprinkler is considered to be remarkable. The velocity of air stream in this ease was estimated at 3-4 m/s.
(4) As for the primary energy of droplets contributing directly to the secondary scattering effect from the surface of leaves, in order to reduce the attenuation of energy of travelling droplets, such means are effective as decreasing the angle of inclination of sprinkler nozzle and lowering the riser height. It is not desirable to make the droplets finer by elevating the water pressure.

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The influence of confining pressure on creep properties of compacted soils at optimum moisture content and the relation among creep strain ε_c, time t, and stress are shown in this paper.
Creep strain of cohesive soil under the same creep stress level is increased with increase of confining pressure, but scarcely influencing on that of sandy soil. The dσ_c/d log t is increased with inereasing confining pressure and creep stress level.
The modified Vialov's equation for creep of soils is not applicable to sandy soil at confining pressure σ₃=1.0kg/cm², so the relation among ε_c, t and stress is expressed by a linear equation of ε_c-log t or log ε_c-log t. The influence of stress on creep strain is taken in the coefficients of the equation. There is a fairly good correlation between the experimental and calculated values obtained by using the relations.

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In this report, we try to analyze the variation of the underground water level caused by the change of the river water level after a new head work is completed.
First, we write the governing equation of the underground water in the finite difference equation based on Crank-Nicholson's implicit scheme, which is said to be very popular and stable to solve a partial differential equation.
Eventually, the equation comes to a so-called 5-point-equation with the underground water level unknown.
On the spacewise domain under consideration are superposed adequate longitudinal and transversal meshes and the time-steps are also set at adequate intervals. So, we form a 5-point-equation at each mesh point. We can determine the underground water level of every mesh point at any time by solving the simultaneous linear equations, formed by assembling all 5-point-equations together and taking into account appropriate boundary conditions.
We apply the present method to the left-side area of the Yoshii River, where the head work is now being built.
We divide the area into paddy field, residential zone and mountaineous area and give different hydraulic costants and percentages of the water going into and out of the underground, and judge the results by comparing the calculated values with the measured ones.
Lastly, we analyze numerically the variation of the underground water level when the river water level is lowered.

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For the planning of freshening reservoirs, the water quantity and water quality are two main factors which must be checked from the standpoints of water use and preservation of good quality of water resources.
So far, the salinity is treated as the most important factor of water quality. But when a freshening reservoir is built at a river mouth, then there is a chance of accepting wastes from towns upstream. The prediction about the effects of those wastes for the water quality in a reservoir becomes especially important.
There are many kinds of environmental factors relating to the water quality of a freshening reservoir, but the typical factors among many relating factors are now under study in many research areas.
The author wants to set the total phosphorus and the total nitrogen as the most important factors relating to the water quality in a reservoir according to the report by the OECD. In this report, the theory of long term simulation for the prediction of total phosphorus and total nitrogen is presented.

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