The effect of the sample area on the statistical distributions of soil physical properties obtained from the plow-sole in a paddy field was examined from a viewpoint of the soil pore structure. Soil samoles were collected with three samplers of different area (6.9, 19.6, 41.2cm²) from the plow-sole in a paddy field and five physical properties such as bulk density were measured in the laboratory experiments. The effect of the sample area on the distribution sof volumetric water content, bulk density, gravimetric water content and volume percenrage of water drained from saturation to the suction greater than 4.9kpa was relatively small and it was statistically equivalent to the fact that the effect of the sample area on the distributions of specific water capacity in suctions greater than 4.9kpa was relatively small. Therefore the area of about 7cm² was sufficient to estimate the distributions of these properties. In addition, the effect of the sample area on the distributions of saturated hydraulic conductivity and volume percentage of water drained from saturation to the suction less than 4.9kpa was relatively large and it was closely related to the fact that the effect of the sample area on the distributions of specific water capacity in suctions less than 4.9kpa was relatively large. Hence, at least the area of 41.2cm² wasneeded to estimate the distributions of these properties.

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Using measured values of soil physical properties in the plow-sole of a paddy field, the author examined the validity of a pore structure model for studying probability distributions of six soil physical properties including saturated hydraulic conductivity. First, the parameters of the model were estimated using a part of the measured values. Second, the expectations of the soil physical properties, which were not used to estimate the parameters of the model, were calculated using the estimated parameters. Third, the author compared the expectations with those directly obtained from the measured values. As a result, the expectations of four physical properties (volume percentage of water drained from suction h-Δh/2 to suction h+Δh/2, volume water percentage drained from saturation to suction h, water content by volume at suction h, bulk density) agreed well with those obtained from the measured values. Only the expectations of saturated hydraulic conductivity did not agreed. Since this disagreement in saturated hydraulic conductivity was proved not to affect the results obtained for other properties, the model was judged to be approximately valid.

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The purpose of this paper is to develop and utilize concrete on which the aquatic life can grow easily. In the first experiment, we observed how well the aquatic life could grow on the mortar mixed with zeolite only, and on the mortar mixed with zeolite and iron, comparing with the plain mortar. The second experiment was carried out to observe whether the marine life could grow more on the mortar containing fly ash and clinker ash with zeolite, and with zeolite and iron, comparing with the plain mortar. The results of the first experiment show that the aquatic life grew much on the mortars with zeolite only, and with zeolite and iron. In the second experiment, the addition of the zeolite and iron to the mortar with the fly ash and clinker ash promotes the growth of the marine life on the mortar.

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The development of greenhouse culture has been outstanding recently in Japan. Almost 80% of greenhouses are composed of plastic houses, and are usually used in the side-opening condition during summer season. An accurate evaluation of water consumption in those greenhouses is important for planning irrigation project. Up to now there is no reliable method for calculating evapotranspiration in the side-opening greenhouse. The experiment on micrometeorological environment in a plastic greenhouse with side-openings showed that regression coefficient and correlation coefficient between wind speed outside and inside the greenhouse change through the growing stages of crop. The results of the multi-point measurement of air temperature and humidity showed that evaporative conditions inside the greenhouse were not severely affected by the advection from outside especially in the maturing stage, as the space of side wall opening was almost closed by the crop canopy. It was found that the Bowen ratio method can be applicable for evaluating the evapotranspiration rate in such microclimatic condition.

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A Simulation model for predicting pesticide concentrations in paddy field (PCPF-1) was evaluated with pretilachlor, commonly used herbicide in rice field in Japan and Asia, using monitoring data obtained at NIAES experimental paddy field. PCPF-1 model prediction of pretilachlor concentrations in paddy water had excellent agreements with observed data for the first week and last two weeks during the 52 days after the herbicide application. However, they were significantly overestimated during the mid period of the simulation. For pretilachlor concentrations in 1 cm surface soil, although slight over estimation occurred during first two weeks, they had excellent agreements with observed data afterwards.
PCPF-1 was used to simulate imaginary conditions in order to evaluate the effects on potential pesticide losses to surface water and ground water due to field drainage and percolation rates resulting from different management practices. The result of the model simulation indicated that 3.0 cm d^-1 and 1.0 cm d^-1 of continuous overflow drainage practices may potentially lose 74% and 63% of applied herbicide to the surface water, respectively. Also, paddy soils having high percolation of 3.0 cm d^-1 and 1.5 cm d^-1 may potentially lose 53% and 38% of applied herbicide below 1.0cm soil surface, respectively. The simulated results suggested that controlling the drainage and percolation are key factors for minimizing the potential pesticide losses into the surface and ground water. The recommended Best Management Practices for the environmental friendly paddy field operation would be minimizing the surface drainage and optimum puddling upon bed preparation to minimize the percolation rate of the paddy field.

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The expansion in the horizontal direction associated with compression (in the vertical direction) is assumed to be the generation factor for vertical cracks leading to hydraulic fracturing. In materials such as metals, the phenomenon causes their characteristics to change from ductile to brittle. In rocks, cracks in the vertical direction are known to form if friction on the top and bottom of the specimen's edges is excluded at a time compression is examined on one axis. Tri-axial compression tests were also conducted on samples taken from a foundation in the actual agricultural reservoir in this research, and the occurrence of a vertical crack was examined under three kinds of conditions. Consequently, a vertical crack may be formed in the specimen by reducing the friction between the specimen and the pedestal as much as possible by the compression in a vertical direction. The specimen with a vertical crack showed a tendency in strength that was similar to the sample without a vertical crack. In addition, it was confirmed that a vertical crack occurred at a considerably early stage in the experiment in which the layer of the disturbed soil was used as the top and bottom of undisturbed soil edges. This suggests the possibility that a vertical crack occurs by built-up of disturbed soil on a foundation when a fill-type dam is actually made.

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Glasshouse experiments in 1997 and 1999 were conducted to investigate two topography related factors, direction toward the sun and slope of a field, and their effects on plant growth. Water was supplied based on average precipitation from July to August in Mu Us desert of Inner Mongolia, China. Two sand slopes with inclination of 20° and 30°, respectively, were planted with grass (F arundinacea Shreber). Four 20° and 30° slopes, two facing south and two facing north respectively, were used. Grass growth and water stress have been concluded with the following results.(1) South-facing slopes received higher radiation which caused higher evapotranspiration and soil moisture loss. This produced water stress under limited irrigation application and stunted grass growth.(2) Water movement from upper to lower slopes caused depletion of soil moisture in the upper slopes. Grass growth in the upper section of the slopes was therefore stunted compared to that in the lower slopes.(3) Force of gravity tended to affect the upward plant growth in higher slopes and causes stress in plant. This reduced grass growth.(4) Climate conditions, soil texture, field size, plant species between our research and Mu Us desert environment have been discussed.

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The authors analyzed upper unit cost of a water environment project. To draw out representative values upper unit cost, analysis of the whisker of the box and whisker plot are effective because the center of distribution shifted to lower values and higher values contain abnormal or mistaken data. On the basis of analysis questionnaires, guide lines for the suitable upper unit project cost are given, which are project cost per acreage, construction cost of toilet, parking, per acreage, and maintenance cost per the acreage or the total project cost.

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The resuspension phenomena of bottom mud in the tidal flat area effect significantly the water-environment and ecosystem of nearshore and estuarine. The purpose of this paper is to study experimentally and theoretically the resuspension mechanism of bottom mud in the tidal flat area under the combined wave and current flows. The movement of bottom mud showed a wavy motion that the horizontal movement was large compared to the vertical one. Both the failure of bottom mud surface layer and the process of bottom mud resuspension were strongly dependent on the bottom mud movement. The temporal variation of bottom mud resuspension rate, which reflects the resuspension process, was roughly divided into three sections. The vertical profiles of maximum shear stress within the bottom mud were analyzed by a multi-layered viscous fluid model. As results, the relationships between the maximum shear stress, the bottom shear stress, or the yield point of bottom mud and the resuspension characteristics of bottom mud were found.

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It seems important to reflect the influence of bottom snowmelt on research regarding the mechanism of river runoff, or on irrigation works projects.
In reality, the amount of bottom snowmelt can be continuously measured only in extremely cold regions where surface snowmelt is unlikely to occur over the long term. And there have been very few examples of estimating the amount during snow cover periods. Thus, it is not an exaggeration to say that the actual bottom snowmelt in snow-covered areas, which can be found in many parts of this country, has yet to be cleared.
In order to improve this situation, 1 1 points where have had clear-cut snow cover periods over the last four years, ranging from Hokkaido to Tohkai Regions, were selected as research subjects. And the amount of bottom snowmelt for each was estimated, and a comparison was conducted.

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Ariake clay deposits are under the normally consolidated condition. In this paper, for undisturbed Ariake clay samples one-dimensional consolidation tests capable of measuring the lateral pressure and isotropic consolidation tests by the conventional triaxial apparatus were carried out to investigate on the coefficient of earth pressure at rest, K₀, compression index, λ, and swelling index, κ. As the result, it was cleared that the K₀-value of Ariake clay in the normal consolidation process indicated the minimum value (0.2-0.5) under the consolidation pressure equal to the consolidation yield stress (equal to the effective overburden pressure) and the constant value (0.45-0.65) under the consolidation pressure 4-6 times greater than the consolidation yield stress. Moreover, it was found that the K₀-value under the overconsolidated condition due to unloading increased in proportion to the m power of overconsolidation ratio, and the value of m was constant (0.46-0.53) to irrespective of plasticity index.

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It is very difficult to design and construct irrigation and drainage canals or chutes in steep slope areas as compared to plain areas, and the cost of construction becomes very high. This is due to the fluctuation of water surface caused by the subtle unevenness of the chute located in steep slope areas, where hydraulic characteristics that differ from the plain areas were observed, because flow with high velocity makes shock waves to take place at the curved portion of the wall of the chute and the ninning water overflows.
Therefore as a solution, this paper presents the development of a new spiral flow control structure of open canal type. The developed structure alters the rectangular canal into a arc shape canal to transform the upward jump energy into the revolved spiral flow energy. Such that it could be constructed at low cost compared to the conventional rectangular canals.

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One of the fundamental problems of farmland policy in today's our country is to adjust the unstable element of long-term food supply and demand, while the structural excess of rice crop products is held short-terminable. In the meantime, in considerable farmland, it intends to have given up the cultivation by adding thing in which agricultural land resorce quantity of present our country has already decreased. Therefore, it is necessary to urgently do the farmland maintenance countermeasure as separately discussing problem of self-sufficiency rate goal to be achieved and problem of agricultural land resorce quantity to be ensured. The gravity of the problem for the basis of the farmland policy is bigger than self-sufficiency rate problem which is related to the utilization of agricultural land resorce, since it is in the maintenance of whole agricultural land resorce.
In this paper, the agricultural land resorce maintenance by extensive management was proposed as a solution for such problems, and the basic concept which is related to extensive management was arranged.

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