Peat is a useful oil absorbent to control marine oil spills and leakage of petroleum-derived hydrocarbons into groundwater. In the present study, the ability of peat as oil absorbent has been assessed by investigating the amount of kerosene retained by the peat packed in cylindrical columns. For comparison, the oil absorbents composed of activated carbon, diatom and polypropylene were also used in the test. It was indicated that the peat is capable of soaking up kerosene to a higher position than other absorbents in an oil absorption process. The peat once saturated with kerosene retained kerosene at a higher position than other absorbents in an oil desorption process. All the absorbents exhibited hysteresis in the retention curves for kerosene, but the extent of hysteresis was the most remarkable for the peat. The densely packed peat soaked up kerosene in greater amount to a higher position than loosely packed one. The sum of kerosene retained by the absorbents in the column and the kerosene retained by the absorbents per unit mass were the greatest for the peat. The remarkable ability to absorb and encapsulate kerosene in the peat would be attributed to fibrous and porous structure and high specific surface area of this material.

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We developed a distributed water circulation model incorporated with reservoir operation, and water allocation and management schemes for large irrigated paddy areas. The water allocation and management schemes have algorithms configured to account for water intake, allocation, and drainage of irrigated paddies. To apply these schemes, we categorized irrigated meshes into representative irrigation systems by exploiting the spatial database of irrigation facilities and beneficiary areas. The reservoir operation scheme has an algorithm used to determine the reservoir releases for irrigation to meet the requirement of downstream diversion weirs, which is typical for Japanese paddy irrigation areas. We describe the integration of these schemes into a distributed water circulation model and discuss how the model facilitates evaluation of the interaction between hydrological cycle and irrigation systems.

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We developed a snowfall/snowmelt model consisting of approximately 1km-square gridded meshes, in which daily snow accumulation and snowmelt are calculated based on the simplified energy balance with precipitation, temperature, wind speed and sunshine duration data. The model was applied to the Seki River Basin, a representative snowy basin amidst a warm climate in Japan. By utilizing satellite images of snow-capped areas, we estimated the spatial distribution of a model parameter of sensible/latent heat transfer in regions where observed meteorological data are sparse. Comparison of the calculated and observed snow water equivalents revealed that the model successfully represents the spatial distributions of snowfall/snowmelt within the ranges of 200mm, except for areas where locally intensive snowfalls occur. In addition, calculated discharges of snow melting periods, obtained by applying the estimated snow melt in each mesh to a distributed water circulation model, showed high accuracy in representation of flood peaks and regressions.

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In this study, a quantitative impact assessment method was developed in order to predict the potential impact of climate change on agricultural water uses. The methodology of this assessment consists of downscaling and bias correction techniques of climate projections from Global Climate Models (GCMs), and a distributed hydrological model incorporating various paddy water uses. This hydrological model estimates the cropping area of rice paddies, the water requirements of paddy fields, diversion water at main irrigation facilities and irrigation water allocation for each paddy field as well as actual evapotranspiration, soil water content and runoff amount. We applied a series of developed methods to the Seki River Basin, an irrigation-dominant basin that experiences heavy snowfall, and carried out the experimental impact assessment of climate change on irrigation water. The results show that snow water equivalents and snowmelt were projected to decrease due to temperature rises in future periods. Consequently, this brought about a decline in river discharge, reservoir storage, and agricultural water intake amounts at diversion weirs during snowmelt seasons. In addition, the decrease in diverted water at irrigation weirs caused the shortage of irrigation water in lower areas of irrigated paddies. These results indicated that the assessment method developed in this study predicts the quantitatively explicit impacts of climate change on agricultural water uses.

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With the goal of using biogas energy not to influence to the effective use of an electric power system, a method of storing and transporting biomethane produced from biogas purification for energy use by local consumers was investigated. The study formulated a model for the use of biomethane produced in a plant capable of treating manure from 1,000 dairy cows as fuel for cogeneration in a consumption area remote from the plant based on mathematical programming. In addition, optimal plant operation to maximize the reduction of greenhouse gas emissions was examined. The results indicated that the optimization of plant operation required the use of a gas engine according to heat demand, the purchase of other power from the electric power system, and gas-boiler supplement for the shortfall in heat. In this case, it was estimated that approximately 500 Nm³/d of biomethane could be supplied to a local area.

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Recently, the deterioration mechanisms of concrete surface of irrigation canals in long-term service have been investigated using the area analysis of electron probe micro analyzer (EPMA). The obtained EPMA data, however, have not shown quantitative information such as a deterioration depth of cement paste portion because of containing both cement paste and aggregate data. Therefore, we have proposed a new method of separating cement paste data using the concentration of silicon and aluminum from EPMA data. As a result, we could separate cement paste data from EPMA data effectively and obtained the quantitative concentration depth profiles of calcium and sulfur that are needed to determine deterioration state.

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The actual conditions of the implementation of the disaster restoration projects in Koi breeding ponds were surveyed, and the location characteristics of the unrestored breeding ponds were analyzed in the M settlement in the Yamakoshi area of the Nagaoka City struck by the Mid-Niigata Prefecture Earthquake in 2004. The findings are as follows: Although the Small-scale Disaster Restoration Project (In Japanese “Tezukuri-tanaoshi-tou-shien” Project) created by the government of Niigata Pref. made a contribution in all of the Koi breeder's classes which were classified by the management scale, a large number of breeding ponds used by the small scale breeders were left unrestored. Moreover, the plots tended to be left unrestored which were smaller, more apart from the road, inclined more sharply, or at higher altitudes. It could be necessary to arrange the facility function and the location of breeding ponds on a normal basis in order to reduce the development of the unrestored ponds.

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To find a robust method for water level measurement based on time domain reflectometry (TDR) under periodic wave conditions, an experimental water level measurement installing the noise filter function in TDR cable tester was conducted and the function effectiveness was examined. In the experiment, changes in water level from the tip of TDR probe were measured in the experimental channel where water surface fluctuations caused by wind, rain, or water current were artificially reproduced with a paddle. In low noise filter level (NFL), TDR waveforms obtained in the water level measurements swayed responding to the water surface fluctuations. In high NFL, the sway was restrained, and it disappeared when NFL was highest of 128. Moreover, most water levels h_TDR evaluated from the waveforms obtained in NFL= 128 were agreed with averaged water levels h_ave, although h_TDR overestimated h_ave under low level conditions. However, the errors under low level conditions could be corrected by the linear function based on h_ave-h_TDR relationship.

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In northeast Thailand the development of on-farm ponds has been promoted by Thai government aiming to shift from traditional farming which mainly depends on sugarcane and cassava to risk distributed farm management system through stabilization of rice production and farm diversification in rainfed agricultural area. In this paper, the impacts caused by the on-farm ponds on agricultural diversification are analyzed through water use survey of ponds water in the study site of Nong Saeng village which is a rainfed agricultural village in the suburb of Khon Kaen in Northeast Thailand. The findings are summarized as follows. 1) Although rainy season rice, sugarcane and cassava are still major agricultural products in Nong Saeng village, the rapid spread of fish cultivation, irrigation to vegetables and fruits have expanded. It can be said the on-farm ponds play the driving force of farm diversification in Nong Saeng village. 2) Also, the cattle raising has changed to keep cattle in the field both day and night. 3) Water of the on-farm ponds in 2010 is used for more multiple purposes than that in 2004. However, the pond water is not used fully in spite of small ponds as shown by the interview survey of the 88 ponds.

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