Operational conditions of an independent photovoltaic generation system were examined by field tests for application to a stirring and aeration machine for treatment of manure slurry. A newly designed stirrer with a screw type rotor driven at 50 rpm or less in a stirring tube could be inserted into a slurry tank and operated with 1.1 kW solar batteries. A DC-AC inverter, which increases the cost, was not necessary if a DC motor was used. Solar battery modules connected in parallel increased the supply current and enabled the machine to run at a low solar radiation of 0.1 kW/m². The viscosity of the stirred and aerated slurry was lowered to 1/2-1/3 of that without treatment. Consequently, the time for transportation of slurry from the storage tank to the field was shortened and a decrease in stench was also recognized upon field scattering.
An independent photovoltaic generation system without storage batteries has large fluctuations in output voltage depending on solar radiation but can be adopted for equipment such as a slurry treatment machine for which operation at a constant rate is not demanded.

View full abstract

Irrigation canals play important roles as ecological corridors that enable seasonal movement of freshwater fishes. Recently. those canals have been modified, which result in abrupt reduction of freshwater fishes. Therefore, it is necessary to develop integrated assessment methods to clarify adverse effects on freshwater fish. However, development the integrated assessment method is difficult since there are problems, for example, spatial complexity, limited availability quantitative data and multidimensional factors that are of different scale. In this paper, we propose to solve these difficulty problems by constructing a spatial model based landscape ecology first and then developing integrated assessment methodology that applied consecutively multivariate analysis. We applied the methodology to data from Egawa River, and the result showed that integrated conservation planning only limited quantitative data.

View full abstract

Spatial analysis of soil salinity, micro-topography, groundwater level and electrical conductivity of groundwater before and after 150mm autumn ponding irrigation (leaching irrigation) was carried out to examine cause of heterogeneous soil salinity distribution in a poor drainage field in the Hetao irrigation district in Inner Mongolia, China. After 150mm of leaching irrigation, soil salinity and groundwater EC decreased, however heterogeneous distribution patterns were not greatly modified. Salt leaching effect was greater near the inlet and decreased towards outlet. Decrease of groundwater EC was small near the inlet and became greater towards outlet. Relationship between micro-topography and soil salinity proves that undulation regulated amount of infiltration water and lead to generating of spatial variability of soil salinity. While fundamental desalinization is difficult because of poor drainage, heterogeneous soil salinity distribution could be reduced to some extent by uniform supply of irrigation water.

View full abstract

Differential settlement of the foundation is a problem in paddy field consolidation. To understand the characteristics of differential settlement in consolidated paddy fields, we examined the problem from the aspect of construction control when the paddy fields are consolidated. We measured changes in the leveling accuracy of consolidated paddy fields and runs of the bulldozer that consolidated the fields. In a district where spreading depth and number of bulldozer compaction runs (construction control) were not well managed, a large amount of settlement occurred around the banks shortly after consolidation. In a district where construction control was well managed, the amount of settlement was small. Two approaches will reduce the amount of settlement: good management of construction control, and leveling after the field foundation has settled.

View full abstract

A theory of one-dimensional consolidation including the secondary one based on the peds model is proposed. This theory is based on the following assumptions;(1) The soil structure is assumed to be composed of the assemblage of peds. Accordingly, it is assumed that the primary consolidation is compression of macro pores among peds by effective stress not between soil particles but between peds and the secondary consolidation, of micro pores within peds by applying of increasing effective stress on peds.(2) The peds are assumed to be linear elastic bodies and the flow of micro pore water within peds is assumed to be governed by non-Darcy's law newly propozed. The consolidation behavior of peds is described by a consolidation function of peds that may be derived from the above two assumptions.
The governing equation with respect to effective stress between peds is derived to be solved analytically by means of the Laplace transform and the primary and secondary consolidation are analytically expressed using the solution of the effective stress. As a check on the reliability of the solution, the settlements measured in the standard tests and the tests with different specimen heights are compared with those predicted by the theory. Good agreement can be observed up to 100-200 in time factor. These resultshow that the H²-scaling law consists in the total consolidation including secondary one and then the practicability of standard consolidation tests may have been raised up to remarkably high grade.

View full abstract

This study discusses a reliable method for both automatic and manual control, and the quantification of control quality with a pH control system. At first, the control time and control quality are faster and higher with automatic control than with manual. Comparing the minimum time of automatic control with the average time of manual control, automatic was 2.5 times as fast as manual. The success rate of manual control was 50 to 60%, while that of automatic was 100%, because with automatic set parameters provide the necessary control. Next, a set pH value was quantified for control quality. A smaller rate of injection volume, -a larger time of stir, and easier judgment conditions facilitate a higher probability of successful control. That is to say that less volume and longer time for injections provides successful control. The results of spectral analysis of injections show that the spectrum slope value of successful control was equal to-0.5. The value of unsuccessful control was equal to-0.9.

View full abstract

Farm land consolidation projects that separate irrigation canal from drainage canal, especially those that dig deep drainage canals divide water area networks harm the habitat of freshwater fishes. This study examined the effects on fish inhabiting paddy fields, ditch and stream when these bodies of water were connected by small-scale fishways after farm land consolidation in Kawachi Town, Tochigi Prefecture. The following facts were revealed. 1) Misgurnus anguillicaudatus moved into the water area network through the small-scale fishways. 2) U-shaped concrete-lined provided a migration pathway for the fish. 3) Paddy fields connected by the small-scale fishways became reproduction fields for Misgurnus anguillicaudatus and Carassius. spp. and spital for the fishes in heavy rain. 4) Increasing drainage frequency facilitated the descent of fish from paddy fields. 5) Earth-lined ditch connected by small-scale fishways functioned as wintering fields for Misgurnus anguillicaudatus and reproduction fields forPseudobagrus tokiensis.

View full abstract

A theoretical analysis of the electronic cone penetration was made based on a three dimensional analysis by using slip line method to determine the electronic cone factor (N_kt). The analysis was made under the assumption that soil was a perfectly plastic rigid material, following Mohr-Coulomb's failure criteria, and that the stresses satisfy Haarvon-Karman's condition. The slip-line fields around the cone tip and in the intermediate transient region in saturated clay were computed under the above conditions for three cases of roughness of cone and shaft surface (ζ) which is also a function of sensitivity ratio of clay and for typical value of cone apex angle 2α=60°C. The bearing capacity factor (N_cp) was presented in terms of roughness of cone and shaft and relative penetration depth. N_kt values, which were calculated based on bearing capacity of the cone, ranged between 9.5 to 14.5 and were compared to fmd included among these values proposed by many other researchers.

View full abstract

Engineers and farmers have wondered why salinization has improved while total salts have accumulated in the Hetao Irrigation District of Inner Mongolia. This study examines cation composition of irrigation water, soil solution, groundwater, and the drainage canal to elucidate that phenomenon. In addition, this study analyzes water-soluble ions and ammonium acetate extracted ions in irrigated and non-irrigated soils. Results of this study include the following:
(1) Electric conductivity (EC) of irrigation water from the Yellow River was relatively low (ca. 1 mS/cm); the sodium adsorption ratio (SAR) was also low (3-5). Nevertheless, EC increased to 3-7 mS/cm. The SAR increased to 7-20 after water passed through the soil. The ground water EC of non-irrigated (saline) land was similar to that of the irrigated land, but the SAR was higher. The cation composition of drainage canal water was nearly identical to that of the ground water.(2) Sodium ion was predominant in water-soluble ions in both the irrigated soils and non-irrigated land; the percentage of sodium in all cations was greater in the saline land than in the irrigated land.(3) The amount of cations extracted by 1 Normal ammonium acetic acid was more than 10 times greater than that extracted by water; the predominant ion was Ca²⁺. The percentage of Ca²⁺ among all cations was greater in the irrigated soils than in the non-irrigated soils.(4) Ca²⁺ in the irrigation water precipitated in soils as insoluble salts.(5) As an index of salt management in the agricultural land, the balance of mobile ions such as sodium is more recommendable than that of the total salt.

View full abstract

Nondestructive examination of hydraulic structure is very important for the estimation of the life cost. While the various examination methods have been proposed for the concrete structure, the results should be compared with the other method to confirm the measured value. The method using the electric exploration is examined for the concrete structure in this paper. Although the electric exploration method is easy and inexpensive, the noise of measurement has to be treated appropriately. Moreover, the electrode has to be designed to be easily attached on the concrete surface. In this paper, the averaging method using the genetic algorism is examined to treat the noise for the tomography. The adhesive pad with metal foil is designed as an electrode, which is found to be successfully functioned. The tomography is used to identify the thickness of the concrete slab. The depth of fracture is also identified with the electric exploration. In this case, the difference between the calculated and measured electric field is examined to infer roughly the depth. This method can give the rough estimation of the fracture depth on the site.

View full abstract

Long-term variability of precipitation characteristics are investigated on the coastal region of Niigata Prefecture, by statistical analysis of daily precipitation series observed at Niigata, Murakami and Takada Meteorological Observatories. Rainfall data at each station is divided into 3 equal terms and analyzed by three hydrologic variables:(1) annual maximum daily value, (2) annual maximum storm total, and (3) annual maximum 3-day value. Snowfall data is divided into 2 equal terms and analyzed by annual maximum daily and storm total values only. Comparison of the frequency analyses across terms shows that within the same Kaetsu district stochastic rainfall has recently increased in Niigata and decreased in Murakami, while the change at Takada located in Joetsu district is small. Correspondingly, the return periods of given rainfall amounts have become shorter in Niigata and longer in Murakami during the most recent term. At Takada the direction of change depends on the hydrologic variable considered. In contrast to the rainfall data, stochastic snowfall has recently decreased in Niigata, Murakami and Takada, although again the change at Takada is small. For all three stations, the return period of a given stochastic snowfall has become longer for the most recent term. Through these results we have shown that local climatic characteristics can be detected and evaluated by statistical analysis of daily precipitation series.

View full abstract

The purpose of this study is to investigate effects of particle size uniformity on solute dispersion for unsaturated granular media. We use uniform-sized and mixed-sized glass beads, the latter consist of particles of three different sizes. Displacement experiments with NaCl solution have been conducted for unsaturated glass beads columns. Breakthrough curves (BTCs) at four depths have been monitored with EC sensors. Dispersivities are determined by fitting analytical solutions of the convection-dispersion equation (CDE) to the observed BTCs at each depth. The solute dispersion in the unsaturated uniform?sized beads shows quite different results from that in the unsaturated mixed-sized beads. In the unsaturated mixed-sized beads, the measured BTCs are well-fitted with the CDE and the dispersivities at each depth show almost the same value. In the unsaturated uniform-sized beads, on the other hand, the dispersivities are much larger than those in uniform-sized beads and the value becomes larger with depth. It appears that the CDE is not applicable to the unsaturated uniform-sized beads columns.

View full abstract

This paper presents the measurement system of localized deformation within saturated sand specimen during shear under plane-strain compression based on the particle image velocimetry (PIV) and the image processing device. Lateral image of the plane-strain compression experiment under undrained condition using saturated Toyoura sand specimen is recorded by the high-speed video and the planar soil deformation is analyzed through the movement of a fine mesh of soil test patches on the image texture. These measurements are converted to the strain and the vortex distribution appeared in the lateral plane of specimen during the shear. After reviewing the underlying strategy of the PIV, a special focus is placed on the evolution of localized strain and vortex pattern.

View full abstract

The distribution of medaka in irrigation and drainage canals was investigated. The investigation was conducted from spring to fall for three years in Uchihizumi area, Kahoku city, Ishikawa prefecture. Medaka began to expand its distribution from the downstream region to upstream at the water temperature above 20°C, and the distribution range was maximized in the mid-summer when the water temperature reached around 30°C. In the upstream region, medaka was distributed mainly in the section where velocity of water current was below 20cm·s^-1. When irrigation was not being done, the fish restricted again its distribution range almost within the downstream region where velocity of water current was below 10cm·s^-1. The downstream region, which has stable water depths and low velocities of water current, was a main habitat of medaka during the survey period. It is considered that the region almost coincided with the section backwatered by West Drainage Catch of Kahokugata and to conserve the environment in the sections is significant for protecting medaka.

View full abstract

Water requirements of non-tilled and tilled paddy fields in lowland areas of the Kita-Tsugaru region, Aomori Prefecture, and the degree of land flatness were examined during six years of non-tilled farming. The following results were obtained: 1. It was shown that water consumption in the initial irrigation period was about 15 mm/d even if non-tilled cultivation had been continued over a long term (six years), and that about 6 days of initial irrigation before rice transplanting was sufficient even if the soil was quite dry. 2. The water requirement of non-tilled paddy fields was 15.3 mm/d in the sixth year and tended to increase with the length of non-tilled cultivation, though it did not increase rapidly since the drainage canal water level was high. 3. Because the degree of land flatness (standard deviation=σ) of the non-tilled paddy fields as determined by 5m mesh was σ=±1.6 cm after six years of farming, there was no remarkable degradation in land flatness due to continuous non-tilled cultivation.

View full abstract

I investigated the performances of monthly water balance models in 4 river basins, located in the upstream of the Tone River, Japan. One monthly water balance model in these river basins is consisted of a monthly water balance sub-model (water sub-model) and a snow-accumulation/snowmelt sub-model (snow sub-model). Combinations of six water sub-models and five snow sub-models were tested. The following conclusions are drawn from this study: 1) the water sub-model should be identified after the identification of the snow sub-model, not simultaneously; 2) the combined model of Moussavi's model and Uehara'snowmelt rate equation is suitable for the snow sub-model, and the Thomas abcd model with the snow sub-model is suitable for the monthly water balance model. The integrated Thomas abed model gives good results with a relativerror of 0.215.

View full abstract

One-dimensional swelling and consolidation tests were carried out to investigate the swelling properties and the consolidation characteristics during loading and reloading processes for undisturbed Ariake clays. The interval swelling index increased almost linearly at the logarithmic overconsolidation ratio below 16, and then showed upward convex curves with increasing the logarithmic overconsolidation ratio. It was recognized that the coefficient of secondary swelling increased linearly with increasing the void ratio at the start of secondary swelling, and the ratio of coefficient of secondary swelling to interval swelling index increased exponentially as the overconsolidation ratio increased. The coefficient of secondary consolidation for reloading process was lower than that for loading process by a half. And it was found that the coefficient of secondary consolidation for overconsolidated and normally consolidated region was determined by using the compression index and the stress ratio of consolidation yield stress or maximum consolidation pressure before unloading to consolidation pressure.

View full abstract

Agricultural canals transport water for irrigation and drainage. Farmers dredge and weed them, maintaining their function of transporting water, and creating a pleasant environment. The amount of money paid to farmers who maintain the multi-functionality of canals has not previously been examined. We investigated the maintenance cost in the Niidazeki Land Improvement District (LID), where urbanization is progressing.
The LID entrusts the maintenance of canals to farmers at very little cost to itself, because it pays the farmers with money collected from them. The multi-functionality of canals is, therefore, maintained through the farmers' labor.

View full abstract