Nitrification in Andisol containing ammonium sulfate was observed at 22, 24 and 26℃ (batch tests). The decrease in ammonium nitrogen (NH₄-N) and increase in nitrate nitrogen (NO₃-N) in the batch tests were simulated well by a first-order transformation. The first-order rate constant decreased dramatically with decreasing temperature. Simultaneously, column experiments, in which ammonium sulfate solution was dripped for 9 d and then pure water was dripped for 20 d, were performed at the same temperature for the batch tests. NH₄-N remained in the upper soil layer due to adsorption, and NO₃-N produced by nitrification leached downward. The NO₃-N production decreased as temperature decreased. Then, using Richard's equation and an advection-dispersion model with Gapon convention for cation exchange and first-order transformation for nitrification, the column experiments were calculated with the rate constant obtained by the batch tests. When dissolved and absorbed NH₄-N were assumed to have the same rate constant, the calculation overestimated the NO₃-N profile in the column experiments. However, the calculation could reproduce the column experiment under the assumption that the absorbed NH₄-N had a smaller rate constant than the dissolved NH₄-N and started to nitrify when the concentration of the dissolved NH₄-N fell below 4 mmol L^-1.

Biostimulation of a petroleum-contaminated soil is a remediation technique that stimulates indigenous microorganisms capable of degrading pollutants with adding of phosphorus, nitrogen compounds, and oxygen. This study is conducted to evaluate the purification effect and influence factors of bioremediation with purification promotion materials including Ryukyu limestone for petroleum-contaminated Kunigami-maji soil, in the northern part of Okinawa Island. Soil remediation tests in our laboratory were conducted to purification characteristics and influential factors for bioremediation. As for the Total Petroleum Hydrocarbons (TPH) removal action, it was confirmed to evaluate purification speed using a primary equation quantitatively. It was confirmed that oil purification speed (removal rate constants of THP) could be improved in the range of 5-20% of water-contents in the soil by adding Ryukyu limestone in contaminated soil more than 5%. It was also clarified that Ryukyu limestone powder (125µm or less) showed the highest TPH purification effect among addition materials of shell pieces and building stones. It was considered that the breathability to be necessary for the metabolism activities of the solution microbe for petroleum-contaminated Kunigami-maji soil, the porous nature of the Ryukyu limestone and the surface was maintained as habitation area of oil solution bacteria. It was suggested that TPH removal performance improved as a result that purification speed was promoted by the activation of the solution microbe, increase in slight biomass, neutralization of the soil.

Slant shear tests and direct shear tests were conducted to determine shear bond strength between inorganic materials. Shear bond strength of bonded interface between mortar and polymer cement mortar (PCM) obtained by slant shear test increased with an increase in compressive strength of PCM, but friction angle didn't change. Since this trend is consistent with general properties of inorganic materials, slant shear test would be a valid method to determine shear bond strength. Shear strength of mortar obtained by direct shear test, which is simpler method than slant shear test, was similar with that calculated from the Mohr-Coulomb failure criterion using compressive and tensile strength. Also, bond property of bonded interface between mortars obtained by direct shear test was similar with that obtained by slant shear test. Therefore, it seems reasonable to conclude that, regarding determination of shear bond strength, direct shear test can be an alternative method to slant shear test.

The objective of this paper is to extend the conventional Darcy-Brinkman equations, which are applicable only to saturated porous region, to unsaturated region because the Darcy-Brinkman equations for the unsaturated region have not be proposed yet. The conventional equations are derived by spatially averaging the Navier-Stokes equations over the saturated domain. Similarly, the extension of the Darcy-Brinkman equations to the unsaturated domain is achieved by spatially averaging the Navier-Stokes equations over the partially saturated porous domain. The extended equations include the time-derivative of volumetric water content in the continuity equation and reveal that viscous and inertia terms and the term derived from the Darcy's law in the equation of motion reflect the characteristics of partial saturation of voids in porous media.

Removal techniques of heavy metals in contaminated soil are sometimes unfeasible because of high cost and/or low efficiency on a large scale, and thus the immobilization process of metals in soils using soil amendments has been gaining prominence as an alternative solution, which aims at suppressing uptake of toxic metals to crops. We focused on the potential of organic matter as an aid in heavy metal-immobilization, and assessed the availability of cow manure and methane fermentation digestive liquid (hereafter, CM and LM respectively) for establishment of safe farming by carrying out batch tests covering Cu, Cd and Pb. The results from the experiments showed that CM had high immobilization effect, especially for Cu, available forms decreased by approximately 90%. However, it was found that the immobilization effect on Cd was less than that on the others and that the mobility of Cd was enhanced under coexistence of other metals, which suggested that the immobilization manner in a dune sand was significantly different among metals as well as environmental conditions. Besides, although the availability of LM was lower than CM, the analysis of speciation indicated that LM also had the potential to reduce phytoavailability of metals.

Through examination of measures taken in the Great East Japan Earthquake and the Niigata Prefecture Chuetsu Earthquake, we discussed the necessity of planned systematic disaster recovery according to the disaster level, and proposed characteristics and composition that the plan should provide. In the agricultural rural development field, planning for disaster recovery is not currently made, but planning for large-scale disasters leads to speeding up and improving efficiency of restoration and reduction of work burden. The disaster recovery plan has the effect of (1) clarifying the recovery policy, (2) reducing the task right after the disaster, and (3) ensuring uniformity of restoration correspondence. Depending on the form of the damage, the afflicted area can be divided into individual damage zone, multi-unit damaged zone, areal damaged zone, and disaster levels are different depending on the combination. In this paper, we categorized disaster levels into three categories, and showed a systematic disaster recovery method for each level.

The tidal response method of analyzing responses of groundwater levels to the tide for estimating aquifer hydraulic parameters was applied to an unconfined coastal aquifer on Tarama Island, Okinawa Prefecture, in order to investigate aquifers beneath wide areas of the island. The method was combined with isolation of specified tidal oscillations by digital filtering and discrete Fourier transform. The length of the used groundwater-level observation data was set based on an appropriate length for the discrete Fourier transform to isolate predominant tidal components, 3,279 hours (about 137 days), and additionally required 10 days for employing prior digital filtering. Estimated hydraulic diffusivities for aquifers beneath several investigation lines in coastal areas of Tarama Island were 4 to 15 m²·s^-1. Hydraulic conductivities estimated therefrom were in the order of magnitude of 10^-2 m·s^-1, the same as the result of a pumping test previously reported. Several coastal parts of the aquifer vary three- to four-fold in estimated diffusivities and conductivities, with smaller values for the northern part and the smallest for the north-northwestern part of the aquifer. This also is consistent with the freshwater-lens distribution biased toward similar directionality.

From this research it is clear that ORP of first aeration tank in intermittent aerobic suspended-growth sewerage treatment facilities should be held in range of 100∼125 mV in order to ensure BOD removal performance, and DO behavior characteristics vary with operation condition such as types of diffused aeration devices, aeration intensity, and aeration time. K_La can be classified by types of diffused aeration devices, and it can be deduced from aeration intensity, temperature and MLSS of aeration tank mixed fluid, also, BOD reaction rate constant can be deduced from aeration intensity, aeration time and temperature of aeration tank mixed fluid. It is shown that operation efficiency of intermittent aerobic suspended-growth sewerage treatment facilities can be improved by choosing the recommend combination of aeration intensity (0.03 m³∙m^-3∙mim^-1) and aeration time (30 min) which is appropriate to the diffused aeration device, as the result, required BOD removal performance can be obtained with less consumption of air quantity.

On grasslands where aerobically digested slurry and methane-fermentation-digested slurry had been applied for up to 8 years, the chemical properties of the surface soil layer and the quality of the grass produced were investigated. The overall mineral balance was found to be favorable and the potassium content in the grass was found to be within an appropriate range, although the potassium content in the surface soil layer was markedly high. The magnesium content of the grass was only slightly above the lower limit of standard magnesium levels. Excessive potassium in the surface soil layer may have inhibited the grass from absorbing magnesium from the soil. The soil analysis suggests that the application of chemical fertilizer should be reduced. It is estimated that on grasslands where aerobically digested slurry and methane-fermentation-digested slurry are applied, zinc and copper tend to accumulate in the surface soil. However, the zinc and copper content levels of the grassland to which slurry had been applied were not significantly different from those of the grassland where only chemical fertilizer had been applied.

Some reports about the 2011 Great East Japan Earthquake, which caused huge tsunami inundation damages, said that road embankments and trenches parallel to the coastlines might reduce the tsunami energy. To mitigate tsunami disasters in coastal agricultural areas, we are planning to introduce drainage channels to reduce tsunami energy, but the effect of sizes of channels to reduction of tsunami energy is not clear. In this study, we conducted a series of hydraulic model experiment tests with the different sizes of drainage channels and the various tsunami energies in order to verify the effect. Consequently, the effect of width of the channels to reduction of the tsunami energies was larger than that of depth. Even if water existed in the channels, the effect could be seen though the effect was a little bit reduced. Effect to the inundation arrival times was also observed.

The hydraulic performance of irrigation and drainage canals is relied on roughness of concrete surface. The arithmetic mean roughness of concrete surface is applied to estimate of the hydraulic performance. The previous study of method for measuring concrete roughness has not been clarified measure underwater. In this study, we focused on that the underwater ultrasonic wave. We considered the propagation loss of measured value, the measuring range, the dispersion of measured value and the between relationship peak to peak and arithmetical mean roughness. The propagation loss amount became larger as the transmission distance is nearer and the propagation loss amount became smaller as the transmission distance is longer. The measurement range from the transmission distance of 500 mm was diameter of about 300 mm. The dispersion of measured value was small regardless of the transmission distance and roughness of the measured surface. The relationship between the peak to peak and the arithmetical mean roughness became high correlation. The results of this study revealed that the underwater ultrasonic wave for concrete roughness could be effective tool.

The participant observation and interviews were conducted in the Yamakoshi area of Nagaoka city struck by the Mid Niigata prefecture Earthquake in 2004 from FY2013 to FY2017 in order to explain the significance of tradition of rural culture. It was revealed that social groups have been organized by tradition of rural culture from the case studies on the partnership between rural communities by community events, the rice farming group, the group for preserving the traditional vegetable “Kagura-nanban” Chili, the urban-rural exchange by community events, the urban-rural exchange by the traditional event “Tsunozuki” Bullfight, and the gathering place for elementary school children after school.

They indicate that administrative support should be prepared for the rural residents to organize social groups voluntarily in terms of disaster restoration and revitalization in rural areas. Therefore, it is desirable to set up the projects with the objective of tradition of rural culture, for example.

This study investigates energy and greenhouse-gas-emission balances of an irrigated agricultural district in an alluvial fan that possesses several small hydropower facilities. We conduct a life cycle assessment on irrigation facilities and crop production based on the inter-prefectural input-output analysis. As a result, we demonstrated that: (1) the irrigation facilities alone produce 12-fold energy as the energy consumption by the facility operations; (2) and still produce 93% of energy consumption when including construction works of the facilities. Furthermore, (3) the produced energy provides 125% of electricity consumption of irrigated agriculture in the district if only paddy and fodder crop productions are considered; (4) and still supplies 51% if more energy-intensive greenhouse horticulture and other crops are included in accordance with the cropping patterns of the district.

In recent years, many techniques, mix designs and construction methods have been studied to reduce concrete cracks. However, the evaluation methods of concrete cracks have not been established and the various methods have been used individual situations, because concrete cracks are caused by various factors. Therefore, this study focused on the concrete drying shrinkage cracks which are found in many agricultural irrigation facilities. Steel ring test was conducted for concrete blended with polypropylene short fibers (PP short fibers), expansive additive and shrinkage reducing admixture (SRA), and the effect of suppressing drying shrinkage cracking was quantitatively evaluated. As a result, it was revealed that the cracks did not occur in concrete with a combination of PP short fibers, expansive additive and SRA, and the effect of suppressing cracking was the highest.

In order to apply repair and reinforcement methods to aged concrete open channels, it is necessary to evaluate their remaining structural strength. In this paper, we suggest the channel wall loading method as a method for evaluating the structural strength of open channels. The channel wall loading method is designed to evaluate the state of deterioration using the slope of the load-deflection relationship. The loading device installed on the top of the side walls of a channel applies load on side walls, and deflection caused by the load is measured by the deflection measurement device. The loading device is capable of outer-side loading (inward loading) and also of inner-side loading (outward loading), and the deflection measurement device can measure deflection in both directions. In this study, these devices are applied to factory-made concrete flumes and the slopes of load-deflection relationships are obtained for both loading directions.

As the result, little difference in slopes is observed in the elastic region. Furthermore, since the measured amount of deflection approximates to its theoretical amount, it is concluded that the amount of deflection by the channel wall loading method can be evaluated by using a theoretical method.

In order to secure the storage performance of the subsurface dam, it is necessary to secure the water-stopping performance of the wall by constructing the water-stopping wall without clearance and by securely grounding it to the base layer (impermeable layer) below the aquifer. In this paper, in order to ensure the grounding to the foundation layer, we investigated a method of estimating the depth of the foundation layer from the data of the load and the current of the speed reducer by the ground improvement machine at the time of constructing the water stop wall by the SMW method. It was confirmed that the relationship between the suspension load and the electrical current changed. In addition, it was confirmed that the injection pressure of the drilling fluid tended to increase when the auger penetrated into the base layer. The method of estimating the depth of the base layer from the change of the injection pressure of the drilling fluid was also examined. From the above examination, it was suggested that the depth of the foundation layer could be estimated from the data acquired from the ground improvement machine at the time of constructing the water stopper wall.

Members of land improvement districts (LIDs) that operate and maintain irrigation/drainage facilities polarize into large-scale agriculture management entities and small-scale farm households. In a general meeting for decision making of a LID, the present method for setting the number of voting rights, “one person one vote”, is advantageous for small-scale farm households because they occupy most of the seats in the LID. For that reason, large-scale agriculture management entities that cultivate most of the farmland in a LID, may be discouraged from fulfilling their duties because they have an inequity in decision making. Therefore, this study proposed and analyzed a new method “adding voting rights according to the area of farmland” with confirmation of the validity of the method using statistical data from a model LID. The following results were observed: (1) the number of voting rights for a member should be the sum of “one per member” and “a number obtained by sharing the subtotal of voting rights, which is equivalent to the number of total members, according to the area of his/her farmland”, and (2) when the new method is introduced, attention must be paid to the promotion of consensus building using workshop techniques within large-scale agriculture management entities before voting.

Fresh groundwater lenses develop on relatively large atoll islands and play a key role in providing stable freshwater supply. The Republic of the Marshall Islands in the Pacific Ocean sometimes suffer from drought caused by El Niño. About half of its population lives in the capital, Majuro, and securing freshwater resources for these people is a crucial issue. There is a fresh groundwater lens (Laura Lens) on Laura Island in Majuro Atoll. In this research, the current status of Laura Lens was investigated as up-coning that mixes seawater into fresh groundwater could render the fresh groundwater lens unusable. Electrical conductivities (ECs) of the groundwater at different depths in the monitoring wells were observed to determine the Laura Lens interface depths. ECs of groundwater surface at resident shallow wells were also observed to determine the planar Laura Lens interface. Locations of these interfaces, which have ECs equivalent to 200 mS/m, were calculated by interpolation. The Laura Lens storage volume from 2010 to 2013 was estimated by inputting the data into Surfer software. The results of groundwater observations showed that up-coning, similar to the one that occurred in 1998 which had resulted in serious drought, could still be observed. It was also found that the Laura Lens storage volume had decreased and that most of the fresh groundwater that seeped into Laura Lens had flowed out into the sea. Therefore, it is necessary to conserve and use the fresh groundwater lens.

Land improvement districts (LIDs) operate and maintain irrigation/drainage facilities that support paddy rice farming in Japan. Organizational management of the LIDs is influenced by changes in water management entities (water user organizations, farmers and legal persons) that arise from changes in the structure of agriculture and rural areas. To avoid serious influences on organizational management, analysis of the effects of changes in the water management entities is essential for determining countermeasures. Therefore, this study qualitatively analyzed the influence of changes in water management entities on organizational management according to five categories, namely membership, decision-making body, executive body, finance and rules. Furthermore, we classified the directions of countermeasures to avoid serious influences “to restrain a cause” and “to adapt an effect”. The following results were observed: (1) increases in the inequity of decision making in LIDs, which resulted from the progress of polarization into large-scale agriculture management entities and small-scale farm households, decreased the willingness of members to fulfill duties in the LIDs, and (2) a direction of countermeasures to increase the willingness was to revise decisions and elections in the LIDs for limiting increases in inequity.

The spatial variability of the ground properties has been modeled as a random field, and the degree of the spatial correlation of the ground properties is represented by correlation length. Generally, determination of the correlation length is difficult, because the testing interval is too long. The purpose of this report is to prepare the basic data to appropriately evaluate the spatial variability of the soil strength by utilizing the correlation length of the soil strength inside an earth-fill dam. For this purpose, cone penetration tests (CPTs) were performed with short intervals at five earth-fill dams, and the correlation length of the soil strength of each the dam in the vertical and the horizontal direction was respectively estimated based on the maximum likelihood method and geostatistical method. As a result, it has been confirmed that the obtained correlation lengths are consistent with the values of the earth-fill dams and clayey soil shown in the past literatures. In addition, as an example to utilize the correlation distance, the evaluation of the spatial distribution of the soil strength inside a dam using the geostatistical method was presented.

The effects of execution or non-execution of initial heating and curing conditions after hardening on the long-term compressive strength of JIS type-II fly ash-based geopolymer paste were experimentally examined. In the case without initial heating, the strength increase due to the material age was not recognizable even under a low humid curing condition. In this case, although there was a disadvantage in that the strength increase was delayed, the curing conditions of a constant temperature and aeration were effective. Next, in the case with initial heating, the curing condition of constant temperature and underwater were effective at the stage of 7 days of material age. On the other hand, in this case, the compressive strengths of long-term material age were decreased in the curing condition of aeration. As a reason for this result, in the curing condition of aeration, the effects of impacts such as the variations of temperature and humidity were assumed to be in comparison with the curing conditions of being underwater and underground.

We conducted the research to clarify the land tenure system and its influence on sprawl of superior agricultural land in Taiwan, by comparison with Japanese system and situation of agricultural land conversion. As results, we found that sprawl in Taiwan is promoted not by conversion of land category from agricultural field into housing site, but by the construction of farm houses on the agricultural field itself. The backgrounds of the latter type of sprawl are followed; 1. multiple usage permitted on legal agricultural field, 2. emancipation of agricultural land to everyone who want to be an agricultural field owner, 3. insufficient operation system and penal regulations, 4. luck of self‐imposed control by local community. For sustainable conservation of agricultural field, these are necessary to regulate usage of agricultural field after sifts of ownership to new entry farmer, and to keep and promote the social capital of local community.

While rural sewerage pipelines were severely damaged by liquefaction of backfill soil during the Niigataken Chuetsu-oki Earthquake in 2007, a large length of the sewerage pipelines, which had been damaged by the liquefaction during the Niigataken Chuetsu Earthquake in 2004 and been repaired by backfilling the sandy soil stabilized by lime admixture, escaped unharmed. In the paper the damages of the rural sewerage pipelines caused by the Niigataken Chuetsu-oki Earthquake in 2007 are investigated to show effectiveness of the liquefaction countermeasure using the backfill soil stabilized by the lime admixture. Then, in order to evaluate quantitatively the liquefaction resistance of the stabilized soil, a series of unconfined compression test is carried out. The test results show that, in the case of addition of 5% quantity in dry mass of lime admixture, the unconfined compression strength of the stabilized soil reaches more than the liquefaction resistance required for of the backfill soil. However, as this strength increases with curing time, some difficulty may be expected in re-excavating the stabilized soil in the future. To solve this, it is recommended that the lime-added soil should be left without compaction during some period before backfilling. It is also shown that the stabilized soil inconveniently decreases its unconfined compression strength after immersing into the water.

Gravel-sand is excavated and sampled from the riverbed beneath the river weir, and its hydraulic permeability is determined by the permeability test using the laboratory flume. Head loss change with flow velocity through the gravel-sand is described by the Forchheimer equation. Nonlinear relationship between the head loss and the flow velocity is compared with the Darcy equation to show that a degree of nonlinearity in hydraulic permeability of the gravel-sand is very mildly to be negligible. This means that, although the gravel-sand includes large particle size stones and gravels, the amount of seepage flow through the gravel-sand is preferentially dominated by the small size particles such as sands and small gravels settling into the skeleton formed by the large size particles. The FEM steady seepage analysis is conducted to study an effect of the nonlinear hydraulic permeability on the seepage flow through the riverbed gravel-sand under the weir floor. It is found that, within a range of hydraulic gradient appearing in the riverbed, the nonlinear hydraulic permeability of the gravel-sand may be well replaced by the Darcy flow without any practical error.

A CASCADE model developed in a previous study can estimate tank water volume based on water balance in a tank cascade system. However, this CASCADE model has not been validated using a data set different from the one used for calibration. In this study, a modified model called CASCADE II was calibrated and validated using with two sets of datasets including rainfall, evaporation, quantity of irrigation water supply, and tank water height. As a result, it was found that the error in the validation stage was 1.1 point higher than that in the calibration stage, and the confidence interval of the error was estimated to be 2.7%-9.8% with a 95% confidence coefficient. It is necessary to review the condition to apply the delay parameter to adjust for runoff delay after a prolonged dry period.

In order to create sustainable life environment, forming “compact villages” in rural areas suffering from depopulation has attracted a lot of attention nowadays. Therefore, it is important to consider locations of life-related facilities. In this paper, we investigated the current situation of life-related facilities' locations in Hakuba Village and Otari Village, which are typical rural areas in Nagano Prefecture. We conducted this research from three points of view: the accessibility of the connection of road networks based on Space Syntax theory, the slope of roads, and population distribution. As a result, we found that Hakuba Village is dominant over Otari Village in regard to the accessibility of the connection of road networks and the slope of roads. Although both villages have a high proportion of population distribution in emergency evacuation areas where people can reach on foot, both villages have a low proportion of population distribution in areas where elderly people can access grocery stores on foot.