Consistency of clayey soils in the plow layer of multi-purpose paddy fields was measured in fresh, air-dried, and oven-dried states. Relationship between the measured consistency and the crop history of the fields was analyzed. Plotting liquid limit (LL), plastic limit (PL), and plasticity index (PI) measured for fresh soil as functions of clay content revealed clear difference in response to the summer crops cultivated just before the sampling: the soils after the cultivation of wetland rice had higher values of LL, PL, and PI than the soils after that of upland crops. The LL, PL, and PI decreased by drying treatments. The difference relative to crop history became smaller by air-drying and almost disappeared by oven-drying. Though the LL and PL measured for air-dried and oven-dried soils were still increased with increase in clay content, the PI was nearly independent of clay content. These qualitative relationships supported the finding that activity, defined as the PI divided by clay content, decreased with increasing clay content. Plasticity index ratio, defined as the ratio of PI measured for the fresh to that measured for the oven-dried soil, is a promising index for the evaluation of change in soil properties resulting from the use of paddy fields for cultivation of upland crops. Whereas the plasticity index ratios measured for the soil under the cultivation of upland crops were smaller than 1.85, those of the soil just after the cropping of wetland rice were larger than 1.85. The plowed soils under the cultivation of wetland rice had plasticity index ratios greater than 2.0, which had decreased considerably from the surface layer at 4 years after the start of cultivation of upland crops, and settled to 1.4 through the plow layer at more than 10 years of cultivation.

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The purpose of this study is to examine the usefulness of the optimum value search method using artificialife (AL) for optimization problems related to planning, design, construction and management in the fields of irrigation, drainage and reclamation as well as infrastructure development. This paper first explains the optimum value search method, then describes the results of the examination of its usefulness using numerical experiments. As one example of an optimization problem, the authors selected the minimum safety factor identification problem in slope stability analysis. The search effects of the AL-applied search method were compared with those obtained by other identification methods, such as the GA method and those using software sold on the market. Our results confirmed that the AL method we describe is far superior to GA method used to identify convergence features, including optimum value search effects. In particular, since the differences of operation parameters have little effect on the search results, the search method using AL is expected to be applicable to a wide range of optimization problems.

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The research was aimed to evaluate the influence of mineral additives on mechanical, mineralogical and morphological properties of mortars under and environment. Fly ash and blast furnace slag were used as mineral substitutive in percentile ratio of 10, 20, 30 and 40, 50, 60 respectively. These specimens were subjected to four different curing regimes: 1) normal curing or immersed in water at 20°C, 2) arid curing with 40°C temperature and 40% relative humidity, 3) 3 days normal curing and then placed in and environment 4) 7 days normal curing and then placed in and condition. The results showed that both fly ash and blast furnace slag additives exhibited higher compressive strength than control mortars under normal conditions whereas under arid conditions the compressive strength did not increase. The strength of mortars increased substantially by water curing in arid environment. The X-Ray Diffraction analyses showed lower peaks of calcium hydroxide in pozzolanic substituted mortars than control specimens under normal conditions. In arid environment dicalcium silicate and tricalcium silicate peaks were emerged along with calcium silicate hydrate and calcium aluminum silicate hydrate. Dispersed micro-structures were seen in and specimens whereas in normal cured specimens regular and arranged microstructures were noticed.

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In the irrigation period from 1999 to: 2001, the influence of fertilizer reduction on outflow loads has been examined. Phosphorus fertilizer is applied using a side fertilizer rice transplanter and coated nitrogen fertilizer is treated in a nursery: box just one time to reduce the mass of fertilizer.
Phosphorus and Nitrogen concentration in standing water and percolated water of the reduced fertilizer division is less than that of the conventional division. Surface and subsurface loads of phosphorus and nitrogen from the reduced fertilizer division are less than those of the conventional division. Outflow loads from the reduced fertilizer division are reduced in comparison to the conventional division by about: 0.6-1kg/ha in phosphorus, 4-6kg/ha in nitrogen, respectively. It seems to be effective for reducing outflow loads from paddy fields that the amount of fertilizer is reduced by using a side fertilizer rice transplanter and a nursery box.

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The Chiruwatsunai River of an arborescent stream system, one of the major natural rivers in Kushiro wetland, is fed by a lot of in-and off-stream springs directly and indirectly, respectively. The in-stream springs are those springing up from the stream bed. The off-stream springs are categorized into two; riparian springs that are distributedso close to the river streams that groundwater temporarily stored in pan-shaped depression after springing up could be supplied to the river via naturally formed open flow path, and hillside springs that are located far from the streams and distributed along the border of low-lying wetland and hilly plateau areas and therefore spreads springing groundwater over the wetland. This paper is associated with field investigations of morphological and hydrochernical aspects of the springs. The main focus is put on the in-stream and riparian springs as well as the river streams. It is found that the springs of interest are morphologically classified into two different types; boiling-sand and crater types which are characteristically distributed along different streams of the river. Through the diagrammatic and clustering analyses of the spring and stream water qualities in terms of geochemical aspects, it is deduced that stream water and different two spring waters are of different origins, i. e., appear on the ground taking different flow paths from their own recharged area. This can be for instance justified by the fact that the water of crater type springs has high electric conductivity and high concentrations of sulfate, bicarbonate, magnesium ion and radon-222, compared with the other waters. It is also shown that springing-up groundwater contributes 20 to 30% of Chiruwatsunai River flow on investigation-time, having significant influences on the hydrological environment of the wetland.

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Channels arranged with natural stones are constructed as irrigation and drainage channels with a concern for the environment. Studies on the hydraulic characteristics and the drag force on roughness elements with regular shapes, such as a cubic shape, have frequently been performed. But it is difficult for us to plan and design channels arranged with natural stones, because few studies of such channels have been conducted until now.
Among a series of studies on the hydraulic characteristics of channels arranged with natural stones, the drag force acting on a single roughness-element settled on a flume bed was measured, and factors influencing that force were analyzed. Important influencing factors were the forms of the stagnation area and the upstream side shapes of the roughness elements.

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The coefficient of consolidation has been determined by fitting manually Terzaghi's one-dimensional consolidation theory to the time-settlement curve in an incremental loading consolidation test. In this paper, a numerical method for the determination of the coefficient of consolidation is proposed. The identification of parameters by using nonlinear least square method derives the coefficient of consolidation. This method has three features; to evaluate the initial offset and the primary consolidation settlement as the conventional method does, to express clearly the deviation between the theoretical and experimental curves, and to construct easily the automatic processing of computation. The coefficient of consolidation determined by this method was greatly higher than that by Casagrande's method, but almost equal to that by Taylor's method. The primary consolidation settlement and initial offset identified by this method also were about the same as those of Taylor's method. Thus, the proposed method could be comparable to the conventional method.

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River water quality investigation was carried out for three years on a forested watershed and a livestock farming watershed in southwestern Hokkaido, Japan. The characteristics of pollution load discharge under three river hydrological conditions (normal flow, rainfall runoff and snowmelt runoff) was examined for both watersheds. The water quality concentration and load discharge were much higher under rainfall runoff and snowmelt runoff than under normal flow. The annual river discharge and nitrogen load were compared for each hydrological condition. It was clarified that more than 50% of the annual river discharge flowed out during snowmelt runoff, and 50% of annual T-N load flowed out during rainfall runoff. Furthermore, NO₃-N load accounted for most of the T-N load during snowmelt runoff, and T-N load during rainfall runoff was predominantly suspended TON load. The annual T-N load discharge was compared between the watersheds. It was found that the annual T-N load in the livestock farming watershed was 1.8 times that in the forested watershed. It was also shown that most of the T-N load from the livestock farming watershed was discharged during the rainstorm runoff.

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The yearly changes in groundwater quality were examined through multivariate analysis by using the data obtained in a near-shore farming area with greenhouse facilities. The changes in cropping patterns seriously affected the variation in nitrate concentration, and its concentration increased year by year at the places where the self-purification rate coefficient had been estimated to be smaller. Cluster analysis revealed that water quality data during the observation period were categorized into four clusters characterized by geological property, fertilization, seawater intrusion, and both fertilization and seawater intrusion. Most sampling sites were fixed in the same cluster, while some sites showed the shift of clusters from the original cluster to another one during the survey period. The amount of fertilizer, watering and fumigation were estimated to be the important factors affecting the variation in groundwater quality.

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The sound characteristics of the flow was investigated for some existing water-cushion type drops, the acoustic sound power level (PWL), A-weighted sound pressure level (L (A)) and the attenuation characteristics of the flow sound in the hydraulic phenomena of the drop flow were examined. The investigation showed as follows;(1) the PWL of the drops measured ranged between 86.6 dB and 104.7 dB, and was greater for drops with greater energy. The PWL and L (A) of the water-cushion type drops were investigated in terms of their energy, expressed as the following different hydraulic factors: discharge, water channel width, drop height (the difference in water level between the upstream drop point and the stilling basin), and the stilling basin depth at the drop point.(2) The PWL and L (A) generated at the drop could be estimated if the hydraulic factors from the relational diagrams for drop energy, PWL and L (A) are known.(3) Judging from its distribution characteristics, the transmission of flow sound in the upstream direction was small, which served as a guide to determining the position of the drop relative to residential areas where the flow sound may cause problems with noise.

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This study dealt with the influence of the conversion biomass application to Shimajiri-maji soil on vegetable growth and soil physical and chemical properties. Two kinds of carbon products, cattle waste and strainedlees of sugarcane Baasse, were mixed into the Shimajiri-maji soil. Change in concentration of nitrate nitrogen in percolating water, soil permeability and available soil moisture were observed. In crop growth experiment, two kinds of by-products of methane fermentation and two kind carbon products were mixed into Shimajiri-maji soil with different ratio. The difference of the concentration of nitrate nitrogenin percolating water and vegetable growth in each pot were clarified.
The results indicated that Shimajiri-maji soil mixed with carbon products, although there was no remarkably change in water permeability, available soil moisture increased. Moreover, the concentration of nitrate nitrogen in percolating water decreased. It was concluded that nitrate nitrogen was denitrified, and ammonium nitrogen have been adsorbed by carbon products. It became clear that by-products of methane fermentation were effective as ammonium sulfate in fertilizer response.

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Recreational excursion of visitors was studied in Daigo Town, Ibaraki prefecture to build a recreational excursion model. The results revealed that some of the major factors that govern the choices of principal destinations are (1) the degree of evaluation, (2) accessibility of information, and (3) whether or not teens and younger children were present in visitors' group. As regards additional destinations, the main factors were found to include (1) whether or not the principal destinations were of the type for long stay, and (2) the distance to other destinations. Using this model, the impact of recreation promoting measures was measured, based on changes in the number of visitors. The study found that, in the case where attractiveness and availability of information were improved at the destination that tended to be chosen as a principal destination (except the long stay type), the visitors increased at that destination and other additional destinations. However, the total number of visitors did not increase in the case of additional destinations. Shortening of the distances among destinations encouraged recreational excursion and increased the total number of visitors.

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Safety design of soil within cofferdam is discussed from the viewpoint of performance-based design for seepage failure. The behavior of soil with respect to seepage failure is first described using test results under a two-dimensional condition (without excavation). The states of soil or three limit states of ultimate, damage and serviceability, are defined, and critical or boundary values describing these states are then given. It is concluded that:
(1) The critical hydraulic head difference for damage is given as the hydraulic head difference at the onset of deformation H_y. The value of H_y is equal to the theoretical critical hydraulic head difference H_PF which is calculated effectively using the Prismatic failure concept.
(2) The critical hydraulic head difference for ultimate level is given as the hydraulic head difference at failure H_f. The value of H_f is given as H_f=1.11 Hy from the test results under the two-dimensional condition (without excavation).
(3) The critical hydraulic head difference for safety construction against seepage failure Hs is given as (0.460-0.733) H_y according to Japanese standards.

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Proper watershed modeling is one of the most essential parts of watershed management. In this study, the performance of Cidanau watershed runoff models based on the Tank Model was evaluated, in view of the models' applicability to water pollution issues. Watershed division for the application of the Tank Model was examined, and the water movement scheme was taken into consideration. The watershed model was expected to perform as a base model for water quality modeling, following which water quality components will be added to the base model structure.

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In this study, the utilization system of set-a-side field by planting of energy crops in Germany is researched and its effects are pointed from a view of rural planning. As a result, it is clarified that not only EU Common Agricultural Policy (CAP), but also Renewable Energy Act (REA) is related to the utilization of set-a-side field. Enforcing CAP and REA at a same time makes appropriate utilization of set-a-side field, especially profitable price for the electricity from small scale generations, using energy crop from set-a-side field. Utilization of set-a-side filed by energy crops have a possibility to strengthen the public function of agriculture, and produce the new additional income for farmers, resulting in total promotion of rural area.

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To comprehend the paddy field ecosystem in Japan, analysis of a food web in aquatic area is required, where material is transported by water and abundant aquatic life inhabits. However, little is known about it. This paper is intended as a review of past food web analysis with stable isotope method, discussing character of producers within an aquatic food web.
Terrestrial organic matter has a role as a basis of a food web as well as algae in a rural aquatic area. In particular, it works actively in Yatsuda (a paddy field at hill-bottom) area, where also algae and organic matter which are generated in a paddy field support a food web in the aquatic ecosystem.
We can recognize that stable isotope method is also effective in a paddy field aquatic area. The method will contribute to execute Agricultural Infrastructure Improvement and Rural Development which gives consideration to truly sustainable ecosystem preservation.

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