In rice double-cropping under direct seeding culture in tropical monsoon areas, uniform and dense germination is essential for both high yield and good weed control.Land leveling is considered to be effective measure for achieving this target.The author carried out examinations in Muda Irrigation Scheme of Malaysia to determine the achievable preciseness of land leveling carried out by motor grader guided by laser beam machine control system.
The preciseness achieved was roughly 3.4 cm in standard deviation in 10 m grid survey after smoothing by drive harrow, in inundated condition.The work rate was approximately 2.6 ha/d. This mode of rapid, low cost and moderately precise land leveling was considered to be necessary for the direct seeding culture, and, therefore, is suggestive for the entire Muda area.
Some more examinations are required to determine the relationship between the preciseness of land leveling and uniform germination, and also on the achievable preciseness of land leveling by other methods, before we can reach any definite conclusions.

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By applying a hydraulic analysis method to data of hydrology and sediment yield from 8 sloping lysimeters with a rain simulator, the following results could be obtained.
1.The lysimeters were 10.0 m long (horizontally), 2.5 m wide and 2.0 m deep.Their slope angles were 5°, 7°, 10°and15°.Two types of soil: volcanic ash soil and sand, were put into the lysimeters and their surfaces were kept bare.
2.The relationships between the mean flow rate and mean rate of transport, which were values of surface runoff and transport divided by the duration of each surface runoff, were improved to such an extent as to be expressed by power regression curves of each gradient for two types of soil.
3.A bed load equation was able to be applied by treating the water-stable aggregate of volcanic ash soil as a single soil particle.The relationships between the mean dimensionless tractive force and mean dimensionless sediment transport based on the bed load equation were expressed by the power regression curves for each type of soil.
4.The water depth at the end of downstream used in a bed load equation could be measured only in the experiment with a rain simulator.Therefore, the equation of the mean sediment transport rate substituting mean water flow for water depth as the variable was obtained as:
q_b=AN^{P (B+0.5)} (sinθ) ^{(1-0.5p) (B+0.5)} q^{-P (B+0.5)} S^-Bd^1-Bg^0.5.
Where q_b is the mean sediment transport rate (g/s/cm), A and B the regression coefficients, P the constant (=0.6), θ the slope angle in gradient, q the mean surface water flow of slope (cm³/s/cm), N the roughness, g the gravity acceleration, d the average diameter, s= (σ-ρ)/ρ, s the density of soil particles in water, σ and ρthe densities of soil particles and water.
5.On the whole, these rate equations were in agreement with the observed sediment transport data obtained with natural and simulated rainfall.When the mean water flow was low and the slope was gentle, however, the application of the rate equation was limited.

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The various and practical methods of determining the zero-plane displacement height, d, were examined by using wind profiles, which were measured in the constant flux layer under the conditions of neutral stability, and by using the friction velocities, u_*, measured by the eddy correlation method.In these methods, the two empirical equations of the power function of elevation, z, and the second-order polynominals in ln (z) were used to fit to measured wind profiles.The value of d was determined from the logarithmic wind profile law by using approximated wind velocities with the empirical equations.The results obtained are summarized as follows:
1) If wind velocities were measured with cup anemometers over a field, then the appropriate value of d could be determined at k=0.39 by using approximated wind velocities with the power function, where k is von Karman's constant. On the other hand, the appropriate value of d could be determined at k=0.35 by using approximated wind velocities with both empirical equations. These two values of d determined here did not agree to each other.
2) If wind velocities were measured with high accuracy, then the appropriate value of d could be determined by the methods applied in 1).The appropriate value of d could be also determined from the logarithmic law by using approximated wind velocities with the second-order polynominals in ln (z), or by using measured wind velocities.These four values of d determined here fairly closely agreed to one another.
3) When the previously proposed flux-profile relationships for wind and others with k=0.4 or 0.35 are extended to a flow over a tall canopy, the value of d can be determined by the respective methods with k=0.39 or 0.35 as shown above.

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In the previous report, the results of a study on the uplift capacity of short piles subjected to various conditions on the frequency and acceleration of horizontal vibration and pile length of embedment were presented.From these experiments, we were able to conclude that the uplift capacity of a pile subjected to horizontal vibrations (Q_D) was much smaller than that without any vibration.The larger the loading weight was, the smaller the frequency, and the larger the acceleration was, the larger Q_D decreased.
We supposed that the matters described above have some close relationship to the horizontal displacement amplitude of a pile.
In this report, so that, we investigated the connection between the decrease in the uplift capacity and amplitude.In these experiments, a pile with a diameter of 43 mm and length of embedment of 20-40 cm, was set into dry sand of two densities: loose and dense.The vibration characteristics for the control had a frequency of between 5-20 Hz with a maximum acceleration of between 50-200cm/s².
From the results of the investigation, the following conclusions could be obtained: The decrease in the uplift capacity of the piles subjected to a horizontal vibration was closely related to the horizontal displacement of the piles.That is to say, the larger the amplitude was, the larger the decrease in the uplift capacity.The reason why the amplitude decreased as time passes was thought to be due to the fact that the sand around the piles became compacted due to the vibration of the piles.

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Medium impact sprinklers with circular and noncircular nozzles were tested in order to make clear the difference of their droplet size distributions and water application patterns, and to evaluate the effect of energy saving by noncircular nozzles.Circular nozzle usually produced greater application radius and larger droplet size at the end of the spray, however, noncircular nozzles gave higher uniformity coefficient than circular nozzles.The main factors affecting droplet diameter at the end of the spray were analyzed and found that nozzle shape is one of the important factors.Analysis of energy saving by noncircular nozzles was conducted and found that the pressure for square nozzle can be 16.7 to 28.6% lower than for circular nozzle for a given discharge.

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Groundwater flows which contribute greatly to landslide are found to concentrate in highly permeable layers and are referred to as groundwater vein streams.
The underground temperature survey method is a simple technique, which not only locates the groundwater vein streams, but also determines the radius and depth of these streams by detecting temperature anomaly at a depth of 1m from the ground surface.Conventional measurements show the representative radius and depth of groundwater vein streams are 6m and 9m respectively.It is essential for the exact estimation of the radius and depth that the distance between measurement points be about 6m or less.
When the underground temperature is measured every 20m, on the other hand, the approximate position of groundwater vein streams can be estimated.In this case, the difference between the temperature at a measurement point and the average temperature of neighboring measurement points provides an useful clue for detection of a temperature anomaly due to groundwater vein streams without considering influences of the topography and land cover.
An underground temperature survey conducted every 20m over a 8ha area resulted in the detection of three groundwater vein streams.The radius and depth of the groundwater vein streams were determined by the survey every 4m.

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A numerical model of steady flow-control and profiles determination in open channel networks is developed. The model is an improvement over a previously developed hydraulic network model, in that the procedure for the solution of channel regulation by flow-control structure (gate or weir) is incorporated.The construction of the model is by a combined use of the finite element method and the Newton-Raphson iterative procedure.The basic equations to be solved are the gradually varied steady flow equations for channels, the semi-empirical stage discharge relationships for rapidly varied flow across a structure, and the energy equations for channel junctions.To ensure functional continuity that the Newton-Raphson scheme requires, the stage discharge relationships which must be altered depending on the outflow regime at the structure are assigned their respective application ranges by compatibility parameters appropriately defined.The gradually varied flow equations are directly cast into algebraic finite element equations by the standard Galerkin procedure, and then the resulting nonlinear equations are adapted into linearized recurrence form by the Newton-Raphson procedure.The channel flow equations so obtained are coupled with similarly linearized equations for structures and junctions to form the global equations system which are iteratively solved.The capability of the model is tested in terms of convergency and accuracy of the solutions to demonstrate that with rapid and stable convergency, the model improved can produce highly accurate solutions to interconnected, regulated network flow problems.

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The time domain reflectometry (TDR), which has been used for the measurement of volumetric soil water content θ, seems theoretically possible to also be applied for the measurement of the depth of frost penetration (frozen depth). Experiments for locating the interface between frozen and unfrozen soil using the TDR were conducted on two soils, a Toyoura sand and a Masa soil.The samples used in the experiments consisted of frozen-unfrozen soil systems in which the artificially frozen soils were placed on top of the unfrozen soils and both layers were adjusted at the same fixed θ values with distilled water or 2000 ppm NaCl solution.Then the results were compared with those from direct measurements of the frozen depth using a ruler.
In these experiments, the results have shown that the TDR can be used to determine the frozen depth with an average absolute error from values by the direct measurements in the used soils of ≅-0.2 and-≅-0.1within 0.28cm and 0.34cm, respectively, regardless whether the soils are saline or not.These findings seem useful for measurement of the frozen depth in fields.

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An approximate solution of describing numerical errors due to the time-line interpolations (numerical damping and dispersion) is analytically derived, which gives a theoretical basis of the combined time-line method of efficiently predicting steady and unsteady flows in pipelines. The accuracy of this solution has been proved to be extremely high through comparisons with numerical solutions. General properties of the numerical errors are investigated based on the analytic solution. The algorithm of designing optimal time step sizes and gridsystems is improved to simpler and more economical one through incorporating the analytic expression of the numerical error into the algorithm.

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To make clear the target values for reclamation of saline soils, both water flow and the transmission of Na⁺ and Cl^- in the roots were studied under hydroponic cultivation using the decapitated soybean root system.The measurement was carried out under the several conditions of both NaCl concentration of culture solution and the imposed sucking force to the cut stump.
As results, transpiration stream concentration factor (TSCF), which was defined as the ratio of ion concentration in the exudation to that in the culture solution, changed with the amount of NaCl dissolved in the culture solution, and was less than unity under the all given experimental condition. This result means that TSCF depended on the physiological function of roots.Water flow in roots, which means of the exudation, was in linear relationship to the driving force, which is defined as a sum of sucking force applied to the cut stump and osmotic pressure caused by differences of concentration between exudation and culture solution.The transmission rates of Na⁺ and Cl^- in roots were also in high correlation to the exudation rate.

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The formation process, distribution, shape characteristics and progressing time of the shallow gullies (recently defined as “ephemeral gully”in America) developed at slopes in the Loess Plateau of China have been investigated under actual conditions.The investigated fields were in ANSAI County, SHAANXI Province and about 2 hundreds shallow gullies were selected and investigated, and the following results were obtained.
(1) In the Loess Plateau of China, sheet erosion occurs mainly near the watershed of a slope, and rill erosion occurs at the upper or middle parts of slope.Shallow gullies develop at the middle or lower parts of slope, occupying about 75% of the slope area.Gullies are formed like a valley at the lower parts of the slope.
From the results of the investigation of ANSAI County, the mean depth of shallow gullies was 1.36 m and the mean width of them was 10m.
(2) The differences in microtopography are enlarged by concentrated rainfall water in deprssed places and shallow gullies are formed by endless repetitions of rill erosion and tillage operation. Defining the characteristics of the distribution of shallow gullies as the distance D (m) between next two shallow gullies, the critical slope length S (m), the critical inclination J°and the critical watershed area A (m²) for development of the shallow gully, mean values of them were as follows: D (m) =16.2m, S (m) =40m, J°=18.2°and A (m²) =657m². The regressive relations between the critical values of inclination (J°) to characteristics D (m), S (m), and A (m²) were obtained using these observation values and shown as a quadratic equation.From these relations, it was found that a slope near 26° had a tendency to undergo shallow gully erosion.
(3) Regarding the shape characteristics of the shallow gully as depth H (m), half width B (m) and coefficient n decided by the degree of development, the cross section of the shallow gully was shown by x-y coordinates.
The period T (years) of development of these shallow gullies was calculated by using formulate on T and result was 36.4 years.

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In Kagawa prefecture, the annual precipitation reaches only about 1100 mm.So from the olden times, many irrigation reservoirs were constructed for agricultural water use.
In pipeline systems which are connected with irrigation reservoirs, if the siphon pipe systems can be used, the construction cost of irrigation systems can be greatly reduced.Because there is no need to excavate the embankment of irrigation reservoirs.
But the accumulation of air is particularly severe problem in a siphon type of pipeline system, since the pressure at the top of the siphon is less than atmospheric pressure.This air seriously reduces the pipeline capacity of transporting water.In the worst case, the water flow in siphon system is stopped.
Accordingly, if we use the siphon system under the negative pressure, it is necessary to evacuate the air from the pipeline for the safety of the flow.Conventionally, the vacuum pump was used to remove the air accumulated in the siphon pipe.But in the case of the vacuum pump method, the water pump is necessary for initial priming of the siphon system and the vacuum pump is not easy for maintenance, so that the vacuum pump method has many disadvantages.
The authors made the new automatic system to remove from the siphon pipe without using the vacuum pump and also made an analysis for the design of the new method of air removal system.
This system of air removal contributes to the promoting of irrigation system of pipeline in the district of many irrigation reservoirs.

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The main concern of this paper is to review the new theoretical and experimental treatments in this decade on the internal hydraulics of two-layer flows over a sill, through a contraction and the combination of a sill and contraction in a channel.By means of three approach methods as to the flow, which two layers are flowing in the same or opposite direction, the conditions for critical flow have been studied to define all of the essential characteristics of internal hydraulics.
First, “minimal approach”assumes Boussinesq approximation. Two-layer flow can be described in dimensionless parameter, known as Internal Froude Number (F_i²). Once the numbers are known, the flow condition through?out the channel can be drawn in Froude Number (FN)-plane.Hence, additional information of channel geometry and discharge relation should be known, in terms of parameters q₂/b, q_r and Y₂'.By then, a virtual control position of internal surface is explained by the FN-plane.This method also can be applied to moderate exchange flow with barotropic flow (U₀) known as Bernoulli potential problems.Using this concept, the characteristics of the flow can be figured such as two examples.
Second, “Characteristic function approach”uses the eigenvalue of two-layer flow matrix equation based on the equations of both continuity and motion.Two set characteristic velocities are obtained as the solution of quartic equation approximation. Based on this, Stability Froude Number (F_s²) facilitated a comprehensive understanding of the hydraulics of two-layer flows.
Third method is “Functional approach”.This is applied to explain an exchange flow in closed channel by Dalziel.Energy difference between two layers is converted into an implicit function in terms of several parameters.Developing these parameter relation, the interface can be determined at certain constriction of the channel geometry.
Further, Lawrence extended Bernoulli potential equation into other dimensionless one in terms of parameters, related to interface position (β_m) and the composite Froude number (G₀²).Both explanations about approach control and a classification scheme to predict the regime of flow is shown with experimental confirmation, provided the values of open-channel geometry, flow rate and lower layer height are given.
Finally, from the point of view of the tidal river flow analysis flow, the applicability of the above three methods are considered.

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[in Japanese]

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