NO₃-N pollution in groundwater is becoming an important issue in the Nasunogahara basin. The aim of the present study is to model the inflow process of the nitrogen load to unconfined aquifers. Based on the analysis of processes of the nitrogen load inflow to groundwater, a water quality tank model was constructed by adding the behavior of the nitrogen load to the existing tank model (Nasunogahara hydrologic model). For formulating the process of inflow of the nitrogen load, L-Q and dissolution types of formulations were considered. Considering the nature of water movement on/in the soil, the L-Q type was applied to the first of the non-paddy field tanks and the dissolution type was applied to the second of the non-paddy field tanks and to the paddy field tank. From this modeling, the trend of change in NO₃-N and the response to precipitation were sufficiently well represented by the model simulation. Results of sensitivity analysis showed that changes in parameter values and conditions of the water quality tank model did not significantly affect calculated results of the change in NO₃-N. On the contrary, slight changes in water movement and water balance in the hydrologic model were found to greatly influence calculated results of water quality. More adequate modeling of the hydrologic process is needed in the future to enable further improvement in the performance of the water quality tank model.

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Under soil conditions of water left over in the field from rainfall and underground springs, drains are needed to quickly get rid of excessive water. A drainage system using drain pipes is an effective technical method in this case. A new clay pipe with many holes. 5mm in diameter at the cylinder wall, was developed for this study. In repeated experiments, the drainage function of the new clay pipe is compared with a clay pipe of the same material but with no holes. As a result of effective drainage by the arch structure that is formed around the holes, soil is prevented from inflowing to the pipes and promotes high drainage. Thus, this new clay pipe can be used as a pipe drain at medium depth in farmland and has proved to be a promising drain material.

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Aim of this paper is to develop the compost demand forecasting methods for planning compost production facilities based on contingent valuation methods. Because it is needed to forecast the demand for compost in the planned beneficiary area before setting the plant, we use contingent valuation methods (payment cards model) as the forecasting method. We show how to collect data (questionnaire) and derive the compost demand functions which draw the relationship between the compost price and quantities bought by farmers. Type of driving the functions is divided two types: 1) aggregate method which is easy to estimate the functions, but difficult to correct the estimation bias. 2) disaggregate method based on econometrics, especially discrete choice models. We apply the method developed in this paper to the case of the facility at Azuma town, Ibaraki prefecture. The result clearly shows that these methods are useful for compost demand forecasting if the overestimating is corrected by using rate of correction.

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The purpose of this paper is to investigate the effects of flow rates and cooling water temperatures to temperature profiles of concrete around a cooling pipe. A series of laboratory tests using specimens (60 × 60 × 50cm) with a cooling pipe was conducted. Various flow rates and cooling water temperatures were adopted in the tests. It was found from the experimental results that the effects of cooling water temperatures to the temperature histories around the pipe were stronger than those of water flow rates. FEM analysis results indicated that the simulation results showed good agreements to the experimental ones.

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The irrigation water flows in the urban area at Kanazawa City, and this is a rare case in Japan. In order to clarify the characteristics of irrigation water at Kanazawa City, the CVM (Contingent Valuation Method) was applied to evaluate the economic value of functions in addition to the main functions (referred to “additional function”). The results obtained were as follow-s;(1) The economic value of the additional function of irrigation water at Kanazawa city was lower than that of rural area. This fact shows that there are differences in people's consciousness between urban and rural areas.(2) The functions of irrigation water in an urban area, such as the means to preserve landscape and to provide easy access to festivals and other people events was given high priority. This means the irrigation water plays an important role in recreational areas.(3) Differences in economic value for each item, having significant values, for CVM, was estimated by the Turnbull scheme and probit-model. The result shows the difference between those two methods was not essential.(4) Consciousness of people toward irrigation water showed difference for each district. The districts having a view of direct irrigation canals were given high priority, in compared with the other districts.

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Thermal conductivity is an important factor in the study of moisture and heat transfer in soils. We gathered soil samples of different quartz content from around Hokkaido and measured their thermal conductivity. We compared the thermal conductivity of soils of varying moisture and quartz content, and examined the applicability of Johansen's method to estimating conductivity.
The thermal conductivity of both frozen and unfrozen soils tended to rise both with increases in quartz content and in moisture content. However, the conductivity varied greatly by soil.
Calculating thermal conductivity using Johansen's method was found to be accurate for soils with a high quartz content. Little applicability of Johansen's method was confirmed for soils with a low quartz content.
However, a modification of Johansen's method facilitates an easy estimation of thermal conductivity for soils with a relatively low quartz content.

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This study develops a quasi-three-dimensional model which practically and economically calculates secondary flows near submerged vegetation zone. This model was obtained by substituting the velocities, U and V, averaged with water depth (U downward and V transverse) which were calculated from SDS & 2DH turbulent flow model into the equations of motion in the three-dimensional downward and transverse directions. The applicability of this calculation method is assured by the results obtained from the previous experiments.

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A grid-based distributed hydrological model is developed to model runoff processes for various land uses. The features of this model are the use of modeling runoff processes of surface water for various land uses in a cell (minimum unit of the model) using a tank model, and calculating water movement between cells by motion and continuous equations. The results show that simulated hydrographs at gauge stations adequately coincide with observed ones; and matching of observed and simulated groundwater hydrographs is better than past results for the Kinu and the Kokai river basins in the Kanto District in eastern Japan. It is confirmed by comparison with past results that the new model of runoff processes of surface water (a recharge source for groundwater), shows i mproved modeling accuracy of groundwater movement, indicating that this modeling strategy is useful.

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One of multi-effects of Farm road improvement project is improvement of rural living convenience by easier access to the center of local life. This paper proposes to evaluate this effect by Hedonic pricing method. Two procedures were used to apply Hedonic pricing method. First, the living convenience was estimated by the accessibility to the center of local life activity. Second, the effect of the farm road was calculated by the land price function, which is explained by general road accessibility. In this case, Hedonic land price function was estimated by a regression analysis of the land prices in the wide area of local life activity centered near Mito city. The effect of Bird Line (the wide area farm road) on the improvement of living convenience was calculated to be approximately 2, 750 yen/m² at the Hiranodai residential area.

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The historical irrigation channel “Hanaguri-Ide” is an open channel of 390 m built in 1608 for Kiyomasa Kato's new reclamation of a rice field. It is said that the tractive force in the Hanaguri-Ide was heightened; leaving contractions with a tunnel bored to the bottom of a partition at a fixed interval, so volcanic ashes from Aso did not accumulate on the channel bottom. In this research, the contractions considered to have existed in the past and the present Hanaguri-Ide were reproduced as a model and water transport capacity, sediment transport ability, and flow structure were clarified by hydraulic model tests. Consequently, it became clear that the tractive force in the Hanaguri-Ide increases markedly as compared to an open channel without contractions, because the flow, which passes through the boring, flows out as a jet. Additionally, the functions of sediment transport and water transport are related in a trade-off, since the contracted tunnel area brings about an increase in flow velocity.

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To estimate the sediment yield from sloping ridged croplands is very important for soil conservation in agricultural lands. Recently, a model for predicting the sediment yield from a sloping field composed of ridge-furrow system was proposed by Nakao et al. In this study, this model was applied to two experimental plots with long furrows (furrow length =50m and 73m). The plots were oriented on the up-and-down slope ridge tillage. Runoff and sediment yield were observed for each plot under each rainfall event during two rainy seasons. Then, sediment yields were calculated by using the predictive model and were compared to observed sediment yields. The results of the application demonstrate that the prediction model should be applicable to predict the sediment yield from a sloping ridged cropland with long furrows.

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A soil erodibility parameter of a soil erosion model is an important factor for predicting the erosion and sediment yield in sloping fields with a ridge-furrow system. Exact prediction of the soil erosion and sediment yield requires a mehod for determining a suitable value of the parameter. However, only a few of effective experimental methods for determining the parameter has been developed. In this study, flow tests were run in furrow channels within a field to develop a simple method of determining the soil erodibility parameter a in a erosion model, E=_aQ^bS^c (E: rill erosion rate, Q: discharge, S: slope, b, c: power coefficients). The results of the experiments indicate that the measurements of sediment runoff rate by flow tests in furrow channels and analyses by using the erosion model can determine a suitable soil erodibility parameter.

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