Koi breeding is one of the basic industries in the Higashiyama area of the Ojiya City and the Old Yamakoshi Village in the mountainous area. Koi breeding ponds, which were the production infrastructures of breeding Koi were struck by the Mid-Niigata Prefecture Earthquake in 2004. The actual conditions of disaster restoration of breeding ponds were surveyed in the S settlement in the Higashiyama area. The findings are as follows: The Small-scale Disaster Restoration Project (In Japanese “Tezukuri-tanaoshi-tou-shien” Project) and the Comprehensive Small-scale Disaster Restoration Project (In Japanese “Kinkyu-tezukuri-tanaoshi-tou-sougou-shien” Project) created by the government of Niigata Pref. made a significant contribution to the restoration of the small scale plots. However the issues of complication of the project's application procedure etc. should be improved. By the management scale and the state of moving out from the settlements in Koi breeder, a large number of ponds used by the small scale moving out breeders were left unrestored. Moreover, some in the class closed their business. It could be necessary to build the restoration apartment block closer to the original settlements in the mountainous area.
In the present study, column and batch tests have been conducted to assess the adsorption ability of lead by marine clay in the presence of salt using lead-spiked DI water, artificial seawater and incinerated ash leachate. Moreover, the migration of lead in the ground where the bottom barrier of coastal landfill sites is assumed is predicted by using the retardation coefficient obtained from the both tests, and refers to the application to the bottom barrier of the coastal landfill sites. Both tests indicate that though the lead adsorption ability is high in the DI water, and decreases in the artificial seawater and the incinerated ash leachate including salts as the concentration of salts rises. Using the adsorption isotherm from batch and column test, prediction of migration of Pb was conducted assuming the bottom barrier of coastal landfill site with HYDRUS-1D. In case of initial concentration of Pb, the result of prediction for column test was evaluated 2.7 times higher than batch test. This is the reason why a column test could consider the pore structure of Marine clay for the evaluation of adsorption.
We got hold of the situation of red soil runoff prediction measures (RSRPM) and farmers' willingness to introduce RSRPM by the questionnaire survey and calculated the amount of red soil runoff (RSR) and the cost of the RSRPM using Monte Carlo (MC) simulation. As the results, the following was recognized. (1)The difference of the subsidy system of the RSRPM influenced the introduction of the RSRPM. Mulching and green-belt were popular for farmers. (2)Farmers' willingness to introduce the RSRPM was more than 90% in the case of the 100% subsidy and decreased in the case of the 50% and 0% subsidy. Farmers who did not have the willingness to introduce the RSRPM in the case of 100% subsidy did not have it in the case of 150% subsidy. (3) There were not differences of the change of the willingness according to the subsidy ratio between two villages. (4) The estimated value of RSR had variance under the condition of the insufficient information and the stochastic grasp of RSR by the MC simulation was effective. (5)There was not the clear relationship between the cost of the RSRPM and the estimated RSR value, but there was the pareto relationship between these values and MC simulation was effective for the preliminary planning evaluation considering the cost-effectiveness.
Using an analytical solution of seepage discharge of rectangular and triangular blankets based on the Bennett model (1945), the thickness and the length of the blanket, which minimize the volume of the blanket on condition that the design seepage discharge is given, are derived as an optimum solution. Based on the decrease rate of the seepage discharge with the blanket length, it is shown that the optimum solution can be used as a design value. The optimum solution demonstrates the ratios of the optimum length, the optimum thickness and the minimum volume for triangular blanket to those for rectangular one become constant. It also shows that if the triangular blanket instead of rectangular one is employed, 31% of blanket material can be saved, keeping the same seepage discharge.
Using an analytical solution of seepage discharge of rectangular and triangular blankets proposed by Bennett (1946) and Yoshitake et al. (2011), respectively, the thickness and the length of the blanket which minimize the seepage discharge under given volume of blanket material are derived as optimum solutions and characteristics of them depending on the blanket volume are described. The results show the ratios of the optimum length and the optimum thickness for triangular blankets to those for rectangular ones are constant. The results also demonstrate that minimum seepage discharge through the optimum triangular blanket is always less than that through the optimum rectangular one under the same volume of the soil blanket.
This paper aims to examine the historical change in the newly developed water resources of Koi breeding ponds in the Higashiyama area of the Ojiya City and the Old Yamakoshi Village. It was clarified that the development of new water resources and the introduction of large pond construction techniques accounted for the rapid increase in the number of Koi breeding ponds after the 1960s. The development of water resources is divided into the following eight stages. 1) before 1945; Koi were bred together with food carps in traditional style, 2) after 1945; breeding ponds were converted from paddy fields under worse production condition, 3) after the mid-1960s; large-scale irrigation ponds in plains were used for breeding Koi, 4) after the 1970s; breeding ponds were converted from paddy fields as a result of the rice production adjustment policy, 5) after the mid-1970s; breeding ponds fed by snowmelt and rainwater were being constructed, 6) after the 1980s; existing breeding ponds were borrowed or bought, 7) after the 1990s; large-scale irrigation ponds in plains were used again for breeding Koi, 8) after 2005; groundwater was pumped up from wells for breeding ponds.
In recent years, national support has been provided to groups that promote conservation of agricultural water resources through joint activities involving the whole community. To continue their efforts, these groups need to take an approach that keeps their members motivated. In this paper, we examined factors that influenced members' willingness to participate in activities that maintained irrigation/drainage canals and analyzed the current situation in a case-study area with a questionnaire given to members. We found that awareness of the necessity for maintenance was the most influential factor affecting willingness to participate, and knowledge of the multifunctionality of water for rural life and the environment had the greatest effect on awareness of necessity in the case-study area. We also found that “maintenance is required for full functionality” should be emphasized as an effective approach.
Yield and cadmium (Cd) content of Arabidopsis halleri ssp. gemmifera were investigated by field experiments in Andisols at two Cd concentrations for three years. The results were as follows: (1) Dry weight of the harvested plant (above-ground part) did not vary significantly for three crops in each field. (2) Cd yield of the harvested plant (above-ground part) for each crop was 927-1,408 g·ha-1 in field A (soil Cd content: 4.9 mg·kg-1) and 122-259 g·ha-1 in field B (soil Cd content: 1.4 mg·kg-1). Cd phytoextraction ability of this plant was similar to that of other phytoextraction plants in Japan, as determined in previous studies. This result showed that Arabidopsis halleri ssp. gemmifera is a promising candidate for phytoextraction of soil Cd. (3) Experimental results on soil Cd changes suggest that the applicability of phytoextraction using this plant is high for slightly Cd-contaminated Andisols. (4) Phytoextraction with Arabidopsis halleri ssp. gemmifera is a viable option for remediation of Cd-contaminated Andisols.
In the cold Tokachi region of Hokkaido there is little snow accumulation, and the soil freezes or suffers from frost heaving. We planted a cut slope there with four indigenous herbaceous species and three indigenous woody species. The test started in September 2005. Thereafter, we maintained a follow-up survey on the percentage of vegetational cover and growth in the plant communities and the change in the composition of plant species until October 2009. The result of the survey shows that every year when the average daytime temperature is more than 5 ºC, indigenous herbaceous plants start budding and sprouting, and extend very rapidly showing more than 80 % of vegetational cover in July. As for the composition of plant species, we recognized mostly 2 species at the beginning. However, many species increased. We recognized this as a successional process. In October 2009 the existing ground coverage was 519-645 g·m-2.
Performance specification for pavement structure design of farm road was established by MAFF in 2005. On the conventional asphalt pavement and concrete pavement, the performance requirement is understood widely, and the performance-based design is almost established. On the sediment pavement typically constructed at the farm road, although the performance requirement is arranged, neither a performance index nor its value is shown. In this research, in order to clarify the performance verification method for farm road, the characteristic of some materials which were applicable to the road surface of the sediment pavement was evaluated. As a result, to evaluate the rutting resistance or the aggregate scattering resistance of the sediment pavement materials, and to estimate the modulus of elasticity are possible by applying a conventional method.
Stomach contents of cut-tailed bagrid catfish (Pseudobagrus tokiensis) juveniles were investigated in a drain of Iwaseki River, Kitakami River system, Iwate prefecture. The samples (n=31) were collected on 29, October, 2009. Aquatic insects were main foods of juveniles of cut-tailed bagrid catfish and it would be related to ecological trait of the species (i.e. benthic fish). Among food species, chironomidae larva were occurred from all of sampled stomachs and accounted for 75.1% of relative abundance of stomach contents. The results of the present study suggested that chironomidae larva would be an important food for juveniles of cut-tailed bagrid catfish.
Fish Populations in small streams are affected by construction of water management facilities that block movement among various habitat patches. Some methods to improve those passage blockages (networking) have been applied but the benefit has not been evaluated preliminarily. We proposed a fish population dynamics model designed for stream networks. In the model, a canal system is depicted using numerous mesh elements which contain habitats separated by passage barriers. The difficulty of movement over the boundary between adjacent mesh elements is given as an attribute value for each element. Accordingly, the points separating habitat areas and the degree of improvement at those points can be depicted using the assigned boundary attributes. Movement distance for each individual is calculated using normal random numbers. Success and failure of movements over each boundary are determined by comparing the boundary's attribute value with a uniform random number. Within each mesh element, reproduction (number of new individuals) is calculated using the logistic growth model. We simulated population dynamics before and after networking of habitat areas in a hypothetical canal system and suggested methods to predict and evaluate the effect of networking of water areas.