A mathematical model was developed to estimate sediment yield from sloping cropland composed of a ridge-furrow system or ridge-furrow and catch canal system. In the new model, the rill erosion model proposed by Takagi et al.(1986, 1989) was used for evaluating erosion in furrows and catch canals. Moreover, Yalin's (1963) equation was incorporated into the model to evaluate the sediment transport capacity of flow at the ends of furrows and catch canal. To verify the applicability of the model, experimental plots (main-plots and sub-plots) were prepared on sloping reclaimed cropland with decomposed granite soil in 1992 and 1993. Ridges on the main-plots in 1992 and 1993 were oriented nearly on the up-and-down slope and the contour, respectively. We observed runoff and sediment yield from experimental plots at rainfall events during the rainy season in each year. A value of parameter related to soil erodibility was determined by using the observed data of the sub-plots. The value was used in calculating sediment yield from the main-plots. Good agreement between the calculated and observed values was obtained. The results suggested that the model was suitable for predicting sediment yield from sloping ridged cropland.

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Comparing a forest basin with a reclaimed farmland basin at Gojo Yoshino in Nara Prefecture, the influences of farmland reclamation of natural forest on water quality and discharge were discussed. Water quality was measured from 22 indices in 1981 and from 1991 to 1994. The results of this study are as follows.
First, the variation of water quality in the reclaimed basin, compared to that of the forest basin, was drastic and there were no particular pattern in seasonal water quality variation. Secondly, present characteristics of water quality in the reclaimed basin have appeared within 3 years after the reclamation work. After reclamation work, annual effluent loads (annual export) of nitrogen, phosphorus and potassium increased over 10 times. In addition, the annual export of sodium, chloride, and dissolved silica increased by abut 20 percent and that of calcium, magnesium, chemical oxygen demand (COD), sulfate and bicarbonate increased in the range of 5 to 8 times. Finally, considering the mass balance of annual import into the both basins (such as precipitation and dry deposits) and annual export from the both basins in 1993, it was found that reclamation removed the cycling of nutrients (such as nitrogen and phosphorus), buffered by the A₀ layer in the forest basin, and increased input/output mass fluxes remarkably.

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Oyachi reservoir, an earth-fill dam recently constructed on a soft foundation (N value <5) composed of pyroclastic silty clay at Tsunan-cho in Niigata Prefecture, suffered a considerable amount of leakage through its foundation when the reservoir water level was raised to an elevation of 653.5 m. Using fundamental mechanical parameters obtained by laboratory tests on undisturbed sample of the foundation soil, FEM analyses were carried out to obtain stresses and strains induced in the soft foundation by the embankment. It was found that a considerable region of the foundation is a state of failure indicating the occurrence of many failure cracks due to extension or compression just after construction. It was also found that the horizontal stresses in the foundation became less than the reservoir water pressure when the reservoir water level was raised to an elevation of 653.5 m.
Based on this evidence mentioned above, it is concluded that the leakage through the foundation zone is caused by hydraulic fracturing leading to the re-opening of pre-existing cracks, suggesting that covering the reservoir slope of the foundation soil with disturbed clayey loam is feasible remedial measures to stop the leakage., This remedial work actually completed undertaken before second test-impounding in 1993 and it was then achieved with complete success, reducing the leakage practically to zero.

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The operators of source reservoir should estimate the irrigation requirement and discharge when the distance between source reservoir and beneficial area is long. The estimation of the irrigation requirement is often difficult because the duty of water at the beneficial area is influenced by rainfall. This is one of the causes of water delivery loss. But the discharge before rainfall can be used later on, if it is saved in the regulating reservoir which is built between source reservoir and beneficial area. The regulating reservoir can decrease the amount of water delivery loss. The capacity of regulating reservoir and the operation of reservoirs for the decrease of water delivery loss are suggested and its effect is showed by the simulation.

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The land cosolidation of lowland lotus fields compared to those of paddy fields were studied.
The results are as follows:
1) Land used for lotus fields has not been improved to the same level as that of paddy fields.
2) The width of the farm roads in lotus fields is suggested to be between 3.5 and 4.3 meters for two trucks to be able to pass each other.
3) Because the roads in lotus fields are likely to be soft, it is necessary that the roads are paved to be stronger and thicker than those of paddy fields and the height of surface road is higher than in paddy fields. The construction costs are higher than those of paddy fields.
4) When the harvesting of lotus roots and the costs of land grading are all taken account, it is considered the length of a farm lot should be at least 100 meters. However, in the area where the subsurface layer has sandy texture, the size of each farm lot should be less than 100 meters, because after land consolidation plowed layer mixed with sandy soil texture produces poor lotus roots.
5) Drainage ditches in lotus growing areas are used only for surface drainage, so they can be shallower than those used in paddy fields.
6) The optimum plowing depth for the best quality and highest yield of lotus roots is 20 to 50 centimeters.

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To obtain aeration most suitable for nitrogen removal in rural sewage facilities, the influence of factors on nitrification rates were examined.
The experiment was performed in an experimental plant. The experimental plant is like a real rural sewage facility consisting of a sequencing batch reactor activated sludge process.
The results are as follows:
The results are as follows:
(1) DO, ORP and ammonia nitrogen concentration changes in the batch reactor had very little influence on the nitrification rate.
(2) It is difficult to know the nitrification condition from pH changes in the batch reactor.
(3) Nitrification in the batch reactor is inhibited by aeration. There is no clear relation between the nitrification rate and water temp. and MLSS in the batch reactor.
(4) The nitrification rate of every water temp. under the condition inhibited by aeration is estimated from an oxgyen uptake rate, a maximum nitrification rate and a maximum endogenous respiration rate of MLSS of every water temp. According to an estimation, it is not necessary to change the aeration.as water temp. changes for maintaining the nitrification rate.

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This research has developed a distribution valve operation system for the discharge of diverted water in the branch-pipeline system. In this system, hydraulic analysis for the steady flow of pipeline can be done in discussion-type format using a personal computer.
The distinguishing feature of this system is that it can derive the opening of valve for the corresponding discharge flow, and vice versa, to determine which valves to operate within the entire valves of pipeline system, and how far these valves should be open.
Finally, the making of adjustment such as matching flow with such constants as flow rate and the loss coefficients of valve for an experimental pipeline and the N-District pipeline has indicated that the discharge can be accurately calculated.

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In this study, in order to gain the data under using portland blast-furnace slag cement in the cold weather region, first we investigated the character of development of compressive strength during low temperature. Secondly, as important durability tests in this region, we examined resistance to freezing and thawing. The obtained results are following.
1) The higher the fineness becomes, the better the consistency of fresh concrete becomes. But the use of air entraining agent inceases.
2) The effect upon compressive strength in early age becomes large by the following order, that is, curing temperature>slag fineness>replacement rate of high early strength portland cement. And the effect in middle and long age becomes large by the following order, that is, slag fineness>curing temperature>replacement rate of high early strength portland cement.
3) When we use portland blast-furnace slag cement on cold weather concrete, we can improve delay of stripping time of concrete form by using slag fineness of about 6, 000 cm²/g over. Moreover we can hasten stripping time of concrete form by using high early strength portland cement and above cement at the same time.
4) When required air content is gained, in spite of difference of fineness, resistance to freezing and thawing of concrete using portland blast-furnace slag cement is insured.

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This study was conducted to clarify suitable materials to perfectly prevent roots form interfering with the water supply for continuous subsurface irrigation using low positive pressure, and soil moisture situation under the cultivation of celery and lettuce.
In this study, three kinds of material were investigated, and experiments were conducted with the planting plot of bleached cotton buried around porous pipe, nonwoven fabric for sink in kitchen, nonwoven fabric for water culture, and untreated. The results obtained are as follows.
1) Extent of roots entangling to the porous pipes was depend on the material applied, roots entangling were perfectly prevented by nonwoven fabric for water culture, and almost by bleached cotton, furthermore, bleached cotton was almost decomposed by bacteria after the term of cultivation. But, roots entangling was seem under the planting plot of nonwoven fabric for sink in kitchen, and untreated.
2) Difference of water supply between former planting plots and latter plots was amounted to about two times. So, Depression of water supply could be avoid by using nonwoven fabric for water culture, and bleached cotton.
3) Therefore, the nonwoven fabric for water culture was judged to be more suitable for the prevention from the depression of water supply ability.

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A simple real-time system for forecasting flood water level at a retardation pond of a pump station was proposed in the previous paper. The flood model in this system is composed of two runoff tanks and one retardation tank, which are operated by the help of a Kalman filtering technique.
In the present paper, first, an optimal set of variances P_diag, U and R, is examined numerically by means of a case study of the Ogura basin. P_diag is the variance of the initial errors of the state variables, U is the variance of system noise, and R is the variance of measurement noise. Next, the possibility of simplifying the system operations, for example by fixing the runoff coefficients of the runoff tanks, by omitting one of the runoff tanks and/or by not modifying the storage of the retardation tank, are studied from the viewpoint of forecasting accuracy of flood water level.
The results are summarized as follows:(1) An optimal set of variances P_diag U and R in the Ogura basin is about 1×10^-3 (m²), 1×10^-2 (m²), and 1×10^-5 (m²), respectively. U and R can be fixed during the filtering process.(2) Flood runoff from the basin is able to represent only one non-linear tank, and the runoff coefficient of this tank can be fixed after being identified by applying the optimization technique.(3) At a pump station where water level fluctuations are violent because of capacity shortage of the retardation pond, the simplification of system operation is usually not possible.

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Plate loading tests for several soils compacted in two cylindrical pits of different size were performed. Repeated loading and impact loading using handy type falling weight deflectometer (HFWD) were applied for these tests. The relation between load intensity and plate deflection from these tests was applied to the theoretically computed graphs, and the values of Poisson's ratio and modulus of deformation of the soils were estimated. Smooth and rough conditions along the side surface of the cylinders were assumed for the theoretical solutions. The results obtained indicated that the difference in the modulus of deformation between the two side surface conditions was less than 7%. The modulus of deformation increased gradually with the number of loading, but the ratio of it after ten thousand times loading to ten times loading was less than about 1.5. Except for dune sand, the ratio of cumulative deflection after million times loading to ten times loading was less than 2. The modulus of deformation obtained from HFWD was less than 60% of that obtained from the unloading process of repeated loading.

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This study presents an identification mehtod of infiltration and roughness parameters for border irrigation. At the begining of an identification procedure, infiltration and roughness parameters are estimated by simple algebraic equations with measurements of rate of advance and surface-water profile. Approximate estimates of the parameters are corrected by an iterative method with an exact solution of the hydrodynamic model. The method was applied to border irrigation tests. Each parameter converged to a certain value after 3 or 4 iterations. Once the parameters are evaluated, rate of advance, surface-water profile and infiltrated water profile ofborder irrigation can be predicted by the hydrodynamic model with various inlet flow rates. In practice, an average infiltrated water along the border has to be estimated by a simple method with reasonable accuracy. To multiply the infiltrated water at an upstream end by a shape factor is a practical method to estimate the average infiltrated water along the border. Equations to calculate the shape factor were assessed based on the infiltrated water profile by simulation. Some of the equations were proved to be able to estimate an accurate value of the shape factor.

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For efficient management of aquifer thermal energy storage [ATES], a fundamental knowledge of coupled heat and moisture transfer in saturated-unsaturated soil zone is required. The heat and moisture transfer experiments have been conducted using an insulated soil column with simulated ground water at the bottom. Experimental data were simulated by using the one-dimensional model of coupled flow considering the heat loss, based on the theory proposed by Milly (1982, 1984). The influences of hydraulic conductivities on the simulation were also investigated, using two estimated hydraulic conductivity functions.
As a result, using the model in this paper, the simulated data approximately coincided with the measured data by estimating parameters adequately. However, in order to simulate better, it is necessary to measure the hydraulic conductivities and water retention curves precisely and to select these model functions carefully. Mechanisms of coupled heat and water transfer by temperature gradients were also clarified by the changes of simulated heat and water fluxes.

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Most of the artificial fish reefs installed on the sandy bottom in shallow sea subside and buried as their surroundings are scoured, thus they lower and lose the function asfish reefs. Scour is related to the properties of sea bottom, flow and the shapes and scale of fish reefs, and it is a phenomenon, of which the quantitative evaluation is extremely difficult.
In this research, in order to estimate the maximum depth of scour the law of similarity that flow and the movement of sand being carried by the flow are similar was derived, and by using the fish reefs of three different scales and the sands of two different particle sizes, the verifying experiment was carried out. As the result, the conclusion that such law of similarity is appropriate that in a real thing and the model, a fish reef and water depth are geometrically similar, and the ratio of shear velocity to the critical shear velocity of sand is similar was obtained.

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Among researches which have been performed in order to analyze the temperature distribution in a concrete structure more accurately, there are numerous ones particularly concerning internal heating in concrete. Of these researches, when analyzing with the adiabatic temperature rise constant (K: the ultimate adiabatic temperature rise, α: the constant pertaining to the rate of temperature rise) being constant within the analysis structure, the analysis temperature may be greatly different from the observed temperature particularly near the surface of the member in some cases. However, the difference in the adiabatic temperature rise constant at various member positions within an actual concrete structure has not been specifically shown.
Thus, on the basis of the temperature measured results at various member positions obtained by the experiments performed in the actual massive concrete pier and concrete box culvert, this paper performed inverse analysis of the adiabatic temperature rise constant optimal for approximation of an observed value for consideration.
As a result, it could be specifically described by using the inverse analysis results that the adiabatic temperature rise constant differs depending on various member positions in a concrete structure. Also, it was found out that the adiabatic temperature rise constant is substantially the same at member positions in the similar ambient environmental state.

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The Bowen ratio energy balance method is one of the most popular methods to estimate latent and sensible heat fluxes from lands. Usually, the temperature and water vapor pressure to calculate the Bowen ratio can not be measured so accurately. Therefore, the estimated values of latent or sensible heat fluxes sometimes do not agree with each other when measurement heights differ. In order to improve the accuracy of estimation, the temperature and water vapor pressure profiles are often smoothed by fitting empirical equations.
In this paper, the necessary condition, which satisfies the assumption that the Bowen ratio is constant in the surface sublayer, to fit the profiles over rough surface into equations is clarified in the Bowen ratio energy balance method. The empirical equation which satisfies such a condition should be used. If the profiles are fitted under this condition with experimental data measured over a paddy field, the estimated latent heat flux or sensible heat flux almost completely agrees with each other using any temperature and water vapor pressure at two different heights. Since the above assumption is not always satisfied when the Bowen ratio is calculated with measurement values, the values of the Bowen ratio are sometimes different depending upon measurement heights.

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In this paper, an effective method for river-mouth improvement has been proposed on the basis of the results of experiments.
Regarding this method, reinforcement of the tractive force and disturbance of the flow and sand movement have been applied. The former is induced by the self-regulating gate system which has been proposed in a previous paper. The latter occurs due to the series bottom pile systems which are set up along the flow near the river mouth.
The gate system caused the river flow to dam up and the water discharged flows down naturally. The rapidly varied unsteady flow with the surge after the opening of the gate board has a large tractive force. Reinforcement of the tractive force occurs due to this flow. The series bottom pile system is made up of several sheet piles arranged in a straight line with proper separations and angles. Two series's of pile system are set up on the right and left hand sides of the main flow near the river mouth. Each sheet pile of the series pile system is arranged so as to converge water flow between the both pile systems and to diverge sediments outside of that region. The sand transported from the main flow region accumulates behind the both pile systems. An especially good water routing system can be obtained in this way.
The optimum arrangement of the piles is also discussed from the results of the movable bed experiments.

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Gypsum is often used to prevent Aluminum toxic problems for plant growth in acid soils. However, subsequent Ca²⁺-Al³⁺ ion exchange could deteriorate soil properties such as aggregate stability and hydraulic conductivity. A lysimeter experiment with a simulated rainfall was carried out to investigate effects of gypsum application on the crust formation at the soil surface, infiltration and runoff during a simulated rainfall. Kunigami mahji soil (Light clay; pH=4.25; EC=0.025 dS m^-1) sampled in Okinawa, Japan, was packed into a lysimeter (30 cm×50 cm×10 cm-depth) placed on a 6° slope. Simulated rainfall of 32 mm h^-1 was applied to the soils with and without gypsum. Changes in exchangeablecations and electrical conductivity of effluents from the lysimeter showed Al³⁺-Ca²⁺ exchange occurred during rainfall. The ion exchange might vary charges on clay particles, resulted in the promotion of dispersion of the soil. Thus, surface crust having much lower conductivity was formed quickly and surface runoff started earlier due to the gypsum application.

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In this paper, the authors examined the representative elementary volume, REV, and the range of influence of saturated hydraulic conductivity, K_s, and bulk density, γ_d, for a field of Andosol in Ibaraki Prefecture. Frequency distributions and semi-variograms of these variables were evaluated for this purpose. Soil sampling was performed as follows. At the nodes of a 1m interval grid, which consisted of 10 rows and 12 columns, soil samples were collected in three different-sized samplers at a depth of 30 cm. Two of these were 2, 356 cm³ (20 cm in diameter and 7.5 cm in height) and 133 cm³ (4.78 cm in diameter and 7.5 cm in height) in volume, and were used in the measurement of K_s. The other one was 100cm³ (5 cm in diameter and 5.1 cm in height) in volume, and was used in the measurement of γ_d. 120 samples were collected in each size. The results are summarized as follows;
1. Measured values of K_s in both sizes were log-normally distributed and no spatial structure was recognized for log-transformed K_s.
2. Notable differences of the mean and the coefficient of variation, CV, of K_s in the two sizes were recognized. That is, the mean of the larger size was 25% larger than that of the smaller size, and the CV of the larger size was 50% larger than that of the smaller size. These results led to the hypothesis that there was an inverse relation between the pore diameter larger than 0.5 mm and the number of pores per unit area in the experimental field. The hypothesis was not inconsistent with the measured soil structure.
3. Measured values of γ_d were normally distributed and the CV was about 7%. No spatial structure was recognized for γ_d.
4. From the consideration of these results, the REV of γ_d was estimated less than 100 cm³ and the range of influence of γ_d was estimated less than 1m. But the REV and the range of influence of K_s were not clear in this study.

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