Since anaerobic digestion effluents (ADEs) contain abundant amounts of ammonium-nitrogen (NH4-N), their agronomic benefits as a liquid fertilizer are expected. However, soil application of ADEs may cause leaching of nitrate-nitrogen (NO3-N) to groundwater. Therefore, effects of mixing organic materials on N dynamics, particularly N leaching from a soil amended with an ADE were evaluated using columns in this study. The different amendments did not cause significant differences in the cumulative amounts of NH4-N leached. The application of sawdust and pruned branch decreased 16% and 22%, respectively, of the cumulative amounts of NO3-N leached compared with that from the soil amended with ADE. It appeared that the organic materials physically absorbed NO3-N against leaching, and caused increased soil microbial biomass to enhance N immobilization to contribute to reduced NO3-N leaching from soils amended with ADE and organic materials.
Accumulation and melting of the snowpack including the role of heat flux from underground was investigated considering the heat balance. Heat balance data were recorded for a period of 4 years at a forest experimental station in Ishikawa Prefecture, which is located in the Hokuriku region of Japan. The findings of the research are as follows. (1) The observed temporal changes in snowpack depth and snow density were well reproduced using our model of snowpack accumulation and melting. (2) From the analysis of temporal changes in input and output heat fluxes of the snowpack, the importance of individual components of heat balance in snowpack accumulation and melting was clarified. (3) Heat fluxes from the surface and bottom of the snowpack in the very cold season accounted for a maximum of about 45% and an average of about 33% of snowmelt at the bottom of the snowpack.
In order to consider a broad array of future planning in local cities, we should focus on three important matters, which are to analyze the transition of land cover and landscape from the viewpoint of the regional characteristics, to predict the future land cover, and to understand the future landscape structure. In this paper, we formulated the prediction method of future land cover based upon the past two satellite data. By using this method, we predicted future land cover in three cities located in the southern region of Lake Biwa, whose population will be growing in the foreseeable future. Furthermore, analyzing quantitatively the regional landscape structure of that areas by using multiple landscape metrics, we investigated land cover changes of the areas from past to future in four different years. As a result, we found the concrete spatial changes of landscape, namely if the present tendency of socioeconomic situation and regional policy does not change, the individual urban areas will continue expanding and combining with each other, and the agricultural land and green space will gradually continue shrinking and decreasing as well.
Laboratory experiments were conducted to study the effect of percolation rate on methane emission from paddy soil during continuous flooding, in order to examine the practical possibility of methane emission control by water management at paddy field sites. Typical formations of paddy field soil layers were reproduced in cylindrical columns without rice plants for measurement of methane emission under various percolation rates. Two experiments were conducted. In Run 1, the percolation rate was fixed at around 10 mm d-1 and 20 mm d-1 to understand the tendencies of methane emission under high and low percolation conditions. In Run 2, the percolation rate was changed stepwise in the range between 5 mm d-1 and 30 mm d-1 to analyze the quantitative relationship between percolation rate and methane emission. It was revealed that the relationship between percolation rate and methane emission is linear with a negative slope. Notably, the slope of the line describing the relationship is affected by the percolation history of the soil. Once the percolation rate reached around 30 mm d-1, which is a very high percolation rate in practical paddy fields, methane emission did not return to the initial value if the percolation rate was decreased. These results suggest that reduced methane emission would be made possible by increasing the percolation rate of practical paddy fields.
To increase service lifetime of irrigation tunnels, many repair and renovation methods have been developed and started to apply. For their proper design, it is necessary to investigate the conditions of tunnel lining and loads onto it. Aiming to develop a method for their estimation, in-situ loading tests are conducted to an excavated irrigation tunnel. Measured deformations and transverse strains are simulated with numerical analyses. Through comparisons of results obtained with loading tests and analyses, conditions of foundation and modulus of ground reaction are estimated. Furthermore, the earth pressure on the tunnel lining is also estimated using the obtained foundation conditions. Based on these processes and results, methods to obtain detailed conditions on and around irrigation tunnels are proposed.
Recently, adoption of pipeline as irrigation channel has increased to be satisfied variety needs of society. For cost reduction, pipelines having larger diameter and thinner wall has been advanced. However, it can be assumed that pipelines having extreme thin wall cause the buckling, and actual buried behavior of pipelines may be different from predicted buried behavior of pipelines at design. In this paper, the model tests for several flexible pipes, which each pipe has a different thickness and equivalent bending ring stiffness were conducted in a steel pit to discuss the influence of the thickness of pipe and ground stiffness behavior of pipes. As a result, it was found that the influence of the thickness of pipe upon the deflection and the distribution of bending strain was extremely small and the larger axial stress acts on the pipe with the thinner wall, and that the change of axial stress in infinitesimal section of pipe was larger with the thinner wall.
The characteristics of the seismic behavior of fill-type dams were examined by shaking table tests, in which three shapes of dam models, namely, symmetric with both a maximum cross section and a dam axis, symmetric with only a dam axis, and asymmetric with both a maximum cross section and a dam axis, were shaken separately in the steam direction and in the dam axis direction, and then the effects of the dam's shape and the direction of the input wave on the seismic response behavior were verified. From the results of the experiment, the point at which the maximum acceleration values were recorded during the shaking in the stream and the dam axis directions was found to be right above the deepest part of the dam's valley. It was clarified that the response orthogonal to the shaking direction could arise depending on the shapes of the dam, the direction, and the dominant frequencies of the input waves. In particular, in the case of shaking in the dam axis direction, the point at which no response could be incited appeared on the crest of the dam depending on the shape of the dam and the dominant frequencies of the input waves.
The methodology to estimate SS loads accurately has not been established yet, because patterns of SS concentration variation are highly complicated and variable. The SALT method employed the probability sampling proportional to the magnitude of loading estimate and was known as an unbiased load estimation method. In this paper, the effectiveness of SALT method in providing a proper interval estimate of SS loads was tested and verified using 10 minute resolution discharge and SS concentration data during 13 months. As a comparison, load estimation method using random sampling and rating curve method was carried out. As a result, load estimates by random sampling and rating curve method had bias even if the sample size was large, however load estimates with SALT method were unbiased and confidence intervals were successfully constructed when the sample size increased.
High-quality aggregate has become increasingly difficult to obtain in Japan. One solution to this problem of dwindling aggregate resources is the effective use of both industrial by-products and low-quality aggregate. In this study, characteristics of drying shrinkage in mortar using various industrial by-products and low-quality aggregate were examined. Crushed sand, recycled sand, granite muck, waste tire, waste glass and two types of fly ash (Type I and Type IV) were used in place of standard sand or cement. As a result, there is a possibility that granite muck had highly utility as fine aggregate because it does not exacerbate drying shrinkage. Waste glass can be used as fine aggregate from the viewpoint of drying shrinkage when the replacement ratio against volume of standard sand is 10% and 30%. The amount of strain in mortar using non-water-absorbing material strongly correlates with mass decrement.
The purposes of this study were to analyze factors causing failures in irrigation-drainage pump stations and improve the efficiency of maintenance management. Analytical data were based on maintenance repair records kept by managers of the pump stations. Shutdown failure of a pump is recognized as a risk, so factors causing failures were determined based on a fault tree. In this study, we confirmed that the frequency of pump shutdowns increased remarkably after operating pumps over 30 years. For efficient risk management, we recommend maintenance repair records be classified, and unusual noises, abnormal vibrations, and start delays be recorded in a daily report.
To provide drain-improving techniques for poorly draining paddy fields, we developed shallow subsurface drain installation implement for tractors owned by farmers. This shallow subsurface drain installation implement can excavate soil, lay a drainage pipe, and throw rice-husk filter material in simultaneously using a 64 kW semi-crawler type tractor. By mounting an uplift prevention device developed to stabilize the soil excavation depth, this shallow subsurface drain installation implement can excavate in about 0.5 m depth and can install a drainage pipe deeper than 0.4 m with subsoil breaking required for farmland management. The shallow subsurface drain outflow rate to the total rainfall was about 14 %. Therefore, an improved effect on the drainage function of the field was achieved.