To consider road problems, it is one of the most troublesome matter to treat volcanic ash soils especially organic ones, which are very often seen in Japan. So it is keenly desired to increase their adaptability for base or sub-base course and subgrade, and to improve their bearing capacity for farm-road, which does not need so strong surface courses, for the progress of the modernized farming.
For these reasons, paying attention to the peculiarity of the Polyvinylalcohol concerning soil stabilization, some experiments were made with “PVA-H”-one of Polyvinylalcohol products-and several remarkable data were obtained as follows;-these experiments were mainly made to confirm the influences of PVA-H on shrinkage, water-stability and strength characteristics of the organo-volcanic ash soil, and to determine the most suitable mixing percentage.-
1. The influence of PVA-H content on shrinkage of the organo-volcanic ash soil is not so remarkable, but when 4% or more is added against dry weight of soils, it seems rather unfavorable, increasing its shrinkage.
2. Water-stability of this soil increases with the increment of PVA-H content. Water-absorption and swelling characteristics, on the contrary, decrease remarkably.
3. As to the influence on the, compacting effect, an increased content of PVA-H leads to an increased maximum dry density of the PVA-H soil, but beyond a certain content-in this case, 1%-this tendency becomes reverse and the maximum dry density becomes smaller.
4. The compressive strength by unconfined compression test is remarkably inflenced by its water content, and the reduction of water content brings the increment of its strength. Moreover, strength characteristics of the PVA-H soil does not correspond with the property of its compacting effect.
Increasing PVA-H content up to 3%, its strength can be increased to 4 times as much as that of the original soil, and this increasing tendency of strength continues with the increment of PVA-H content. Therfore, these data suggest that the properties of PVA-H would be very useful to improve the organ, ovolcanic ash soil.

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It has been desired to establish a simple and appropriate method for lining canals and ditches for irrigation and drainage.
Attention was paid to the peculiar concretion phenomenon of soils by Polyvinylalcohol, and several experiments were made on the application of PVA-H, a kind of Polyvinylalcohol Products, for such lining.
After sprinkling PVA-H solution of different concentrations over soil surface, tests were made on the treated soil layer as to its adhesion to the original soil layer, the prevention of failure along craks, its water-tightness And its water-stability.
Two kinds of sandy loam were used to test these probrems. The results are as follows:
1. The adhesion of the treated soil layer to the original soil layer may be considered to depend on the concentration of solution and the depth of its infiltration; data show that the dilute solution under 296 brings good result, and the concentrated solution of about 3% or more causes a separation of the treated soil layer from the original soil layer.
2. Cracks develop owing to the shrinkage characteristics. The characteristics can be improved by the treatment with PVA-H solution. However, there is little difference among the effects by variously concentrated solutions.
3. In order to prevent from the percolation of water, it is required to treat with 3% solution of PVAH, and similar impervious layer can be obtained by repeated sprinkling of more dilute solutions.
4. The water-stability seems to be good except to mechanical shocks. These data seem to show that repeated sprinkling of such a dilute PVA-H solution as 1-2% brings the, most favorable condition for lining canals and ditches.

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Recently the use of tractors has gradually increased in rice field. There the wheels sink into the soil in inverse proportion to the mean contacting earth pressure and in the worst case the operation of tractors becomes impossible.
The authors experimentally made a diagram showing the relation between the penetrating resistance and the wheel sinking of the four tractors such as TC-10, AT-5, DEXTA and Super DEXTA, found a practical method to acquire the wheel sinking value through the penetration test and soil test before the tractors are introduced onto the field and also studied characteristics of the four models with the diagram showing the relation between the penetrating resistance and the mean contacting earth pressure.

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Comparison was made between the annual evaporation from forest lands and the computed potential evapotranspirations. The evaporation was computed from the measured runoff at the four runoff experiment stations of the Governmental Forest Experiment Station of Japan. It was recognized that the mean annual evaporation appoximately coincided with the computed potential evapotranspiration by Thornthwaite's mehtod for the northern region higher than 40 degrees N. L. and by Author's method for the region lower than that.
Six portable evapotranspirometers were established in the court of Shiga Prefectural Junior College and evapotranspiration (ET) and potential evapotranspiration (PE) were measured in grass plots and bare plots. The ratio of ET to PE ranged from 1 to 0.6 for each of the both plots.
Surface runoff and seepage were measured in order to know the effect of the humus layers in forest lands where grow typical Japanese species of trees, the cryptomeria (I), the Japanese cypress (II), the red pine (III) and broadleaved trees (IV), on runoff.
The soil tanks used in the experiment were 15 cm wide, 60cm long, 10cm deep and had a seepage orifice of 1cm in diameter at the center of its lower bottom. The surface soil of the granitic forest land near the College was put in the soil tanks under the natural condition. The tanks were placed on the stand with variable slopes (20, 30 and 40 degrees), and artificial rainfall of intensity about 1 to 3mm per minute was applied on them.
Runoff and seepage were measured each 5 minutes until constant values were obtained. The mean values of the final runoff from the soil tanks of each species of trees were: I: 72%, II: 65%, III: 48% and IV: 58%. And the steeper the slope of tank was, the smaller Was the difference of runoff coefficients by the species.
The measured evapotranspiration coefficients of trees were: the red pine: 0.7-0.8, the cryptomeria: 0.8, Chinese anise (an evergreen broad-leaved tree): 0.5-0.6, maple (a deciduous tree): 0.6.
It is assumed that the maximum deviation of soil moisture storage is about 170 to 180mm from the results of the measurements of soil moisture in the surfce layer, mainly humid brown forest soil, of 11 forest lands in Japan.
It is intended to induce a formula for computing runoff coefficient by applying the above results and by investigating the daily runoff at the four runoff experiment stations.

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The quantity of daily snow-melt is considered analytically and numerically under constant density of snow-cover as follows:
i) By applying the heat conservation law on the snow-cover and on the convection layer of the atmosphere, an analytical expression was reduced for the daily snow-melt, that is the daily decrease of the snow-cover h by the form
h=β₀+β₁Δθ+β₂θ
where θis the daily mean air temperature, Δits increase between two successive days, and and β₀, β₁, β₂, constants defined from the meteorological constants.
ii) Furthermore, if one assumes that the solar radiation in the period of the snow-melt varies linearly with the time t, the time dependence of θ and h are formulated, and also the height of the snowcover H is shown as
H=H₀-γ₁t-γ₂t²,
where H₀, γ₁, γ₂are constants. Therefore, the beginning and the final time of the snow-melt are obtained.
iii) Both results above mentioned are formally successful, whereas their numerical estimations are not satisfactory. It is noticed that a good fit withexperiments is reduced from the assumption that the real heat loss by black body radiation from the snow surface is much smaller than its calculated value.

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In this paper, the velocity and pressure distributions in the flow over a weir and the pressure distribution along a weir face have been studied.
The equations were obtained useing only the assumption that shows the relation between the inclinded angle of stream line and its position in the cross-section of stream. The distributions can be found by these equations despite of the various shapes of water profile and weir face and the calculated results shown a better agreement with test data than the results by hitherto method.
And then, from these results, it was found that the distributions were affected by a mere variation of water profile and weir face.

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The transpiration of the rice plant cultivated in paddy field depends mainly on its leaf area index (L. A. I.) and meteorological conditions. The transpiration from unit leaf area decreases with increase of L. A. L and when the rice plant grows to have L. A. I.=6-7 in its process of growth, its transpiration does not increase furthermore. Therefore L. A. I.=6-7 is the cardinal number of cultivation under the meteorological condition of the year. In order to obtain knowledges on the march of transpiration through the whole growing season, authors deviced “transpiration efficiency” and examined the transpiration of each growing stage by this conception to find out the transpiration efficiency decreasing from about 30% to a half of that in proportion to growth.
To clarify the mechanism of this decrease, authors made clear the vertical distribution of transpiration within the plant cover on the viewpoint of energy balance and found out that the transpiration intensity of the plant canopy is much higher than that of lower layer. By this investigation the main factor commanding that decrease was clarified.

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The evaporation from ponded water surface of paddy field under the vegetable cover is a physical phenomenon, and is approximated by the following type of equation which involves a kind of plant growth index (L. A. I.) E=_λE_pexp (-βL)
Energy must be supplied to the evaporation system for the continuation of evaporation and the main energy source is the solar radiation which penetrates the plant layer to the water surface. Then authors reduced the following equation on the daily evaporation in the above-mentioned viewpoint.
E_c=R₁ζexp (-1/2KL)
By this equation, the daily evaporation from water surface of paddy field both with and without rice plant is to be estimated. Energy available for evaporation from paddy field without rice plant is about65.1% of the solar radiation above the plant layer on a daily basis.
A portion of solar radiation which arrives at water surface is inverted into other environmental elements than the latent heat flux, such as the radiation which is reflected on the water surface, sensible heat flux, soil heat flux, etc. The ratio of the sum of these elements to the solar radiation above the vegetable cover is expressed by the following equation:
M=exp (-KL){1-ζexp (1/2KL)}
The validity of this equation is within the limit of normal growth. This equation gives M=-0.349, M<0, M=0 and M>0 respectively for the cases where L= 0, O<L<1, 752, L=1.752 and L>1.752.

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Analysis of Salt Wedge in the estuary is very important in Japan now. It is very dificult, however, to carry out theoretical analysis by the fundamental differential equation of motion of salt wedge. Poggi's or Morgan and Farmer's solution are nothing more than a practical equations. At present, fortunately, digitial computers are common in Institutes and Uneversities in Japan. The characteristics of salt wedge in estuary was studied by, the computer KDC-1 of Kyoto University. By this numerical analysis, several characteristics of salt wedge were known as are presented in this paper.

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