In Yokoyama district, Shiga Prefecture, water budgets in large-sized paddy fields with 3 different cultivation methods were measured from 1995 to 1999, and in-persons interview survey was made in 1998 and 2001. Direct seeding culture in a flooded paddy field (DF), direct seeding culture in a well-drained paddy field (DW) and traditional transplanting culture (TC) were compared. Measurement of water budgets after the early stage of irrigation shows that DF bear a similarity to TC for time series behavior of water demand, and that the behavior in DW is different from the others. It is also regard that water management for DF is analogous to that of TC because of the relation of water requirement rate between before and after mid-summer drainage. Therefore, it takes more time for DW to be established since being introduced than the other cultivations. The interview survey makes it appear that unless the direct seeding culture combined with TC under certain size of farm, it would not give full scope to its advantage.

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Integrated study of boring investigation, electric and temperature loggings and monitor data of vertical electric conductivity for design and execution of underground dam reveals the real conditions of salt water intrusion into a Ryukyu limestone aquifer. Vertical distributions of electric conductivity in limestone with cave show various form frot`n place to place and from hour to hour. Differences of various form are classified into 6 types; A F. A type, which is distributed in inland area except a small area around Suuga costal spring, is regarded as no intrusion of salt water. B, C, and F types show a discontinuous change of vertical distribution of electric conductivity with bending point. These types are well known typical form of salt water intrusion in aquifer with dispersion flow in a initial stage of the evolution of karst aquifer. D type shows a gradual change of vertical distribution of electric conductivity from fresh water to salt water with depth. E type shows a homogeneous high electric conductivity part from ground water table to a certain depth. D and E types may be characteristic types in karst aquifer because typical phenomena of karst aquifer that several hundreds meters wide of brackish zone are distributed is occurred around areas of D and E types. It is considered that the Ryukyu limestone on the whole in Komesu underground basin is in a middle stage of the evolution of karst aquifer

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Solar radiation is one of the most important factors which affects the water consumption in the crop fields. The distribution of the sunlit and shading portions on the soil surface between rows complicates the solar radiation environment. The amount of solar radiation transmitting on the soil surface depends on not only crop types and growth stages but also meteorological, topographical and astronomical conditions.
To estimate the complex solar radiation environment on the soil surface, two types of crop canopy architectural models expressing the specific row crops are introduced. The rectangle tube model represents the condition that the crops are contacted each other in the row direction, and the cone model represents the condition that crops are separated each other in any direction.
Solar radiation reaching to the soil surface can be separated into the direct solar radiation and the diffuse sky radiation. To quantify these components separately, the orthographic fish-eye projection method was applied. The amount of solar radiation between rows estimated by this method showed good agreement with the values observed in the field. The ratios of ground cover by the rectangle tube model and the cone model are about 33 % and 19 %, respectively.

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Sustainability of efforts of development aid in developing countries through the Participatory Development Method (PDM), which is at present attracting attention, is not attainable in many cases. Against this background, the authors proposed the Autonomy-Support Development Method (ASDM), which involves certain concrete steps for inspiring beneficiary farmers to support themselves in addition to their participation in the project. In case of the soil and water conservation project in Bolivia, farmers' concern with the project, their sense of ownership, and management ability of the farming community were improved through the ASDM thereby confirming the theoretical validity and effectiveness of the ASDM. The ASDM is a method modified from the PDM to make it more concrete as a concept. In order that farmers can make their own decisions by themselves and assume development responsibilities in their community areas after aid organization has left, the following recommendations are proposed as indispensable prerequisites; 1) Capacity building aimed at improving farmers awareness and knowledge about their problems and enhancing their sense of ownership of the project including its outputs, 2) Training leaders of the farming community who may assume development responsibilities of their respective community area, and 3) Systematical transfer of decision-making initiative from the aid organizations to farmers.

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Improvement method of permeability of Lake Kojima Sediment with hydrated lime and gypsum were investigated. Three application methods were compared in the saturated hydraulic conductivity experiment; mixing, surface distribution and solution percolation. Lime has been used for soil stabilization for a long time and the stabilized soil permeability was considered to become low. However, our experiment showed that hydrated lime application with mixing maintained high hydraulic conductivity. The soil structure was supposed to be stabilized by chemical reaction between soil and heterogeneously distributed hydrated lime. On the other hand, gypsum application with solution percolation maintained the same hydraulic conductivity as that of hydrated lime application with mixing. In that case, electrostatic adsorption of Ca was considered to generate flocculation and kept high permeability.

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We established, calibrated, and validated a distributed hydrological model for the Thiba catchment in central Kenya. In the 1990s the catchment experienced a sharp increase in the use of water for agriculture. This study represents the first step in modelling the effect of distributed irrigation activities on the river regime in the catchment. The hydrological processes considered were snowmelt, interception, evapotranspiration, overland flow, channel flow, inter-layer drainage, and lateral saturated flow, which were modelled either by finite difference approximation of partial differential equations or by empirical equations derived from the literature. A digital elevation model of cell size 500 m by 500 m was used. The simulated daily runoff showed fairly good agreement with the observed runoff at 2 out of 3 gauging stations. The discrepancy at the last station may have been due to observation error. We confirmed the model's ability to simulate daily runoff.

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For moderately concentrated suspensions of kaolinite, effects of solid fraction and temperature on the viscosities were discussed. Kaolinite suspensions were prepared for solid fraction of 20, 25, 30 and 35%. Then, viscosities of each samples were measured for 90 minutes by cone and plate viscometer, at six levels of temperatures of every 5°C from 15°C to 40°C. Since it varied with elapsed time of measurement, initial viscosities η_i measured at the first ten seconds were picked up and examined on these effects.
Experimental results indicate that in η_i is proportional to solid fraction of samples, and the relationship between in η_i and temperature may follow Andrade's equation. Based on these results, the equations, as functions of solid fraction and temperature, were proposed newly within the range of this experimental condition. Three constants involved in the proposed equation were estimated from experimental results on this study by regression analysis.

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A method is developed to optimally allocate allowable pollutant loads from non-point sources in a watershed using multiobjective optimization theory and Geographic Information System (GIS). Using calculated values of flow length from each land management unit (LMU), which is represented by a grid of uniform size, to the outlet in the watershed, and assumed value of watershed-wide self-purification coefficient, a two-objective linear programming model is formulated. The objective function maximizes total allowable discharged pollutant loads from LMUs and promotes equal allocation of them in a selected sub-watershed, subject to constraints of effluent limitation at the outlet of the sub-watershed, relation among mean effluents from different types of LMUs, and minimum limit of effluent in each LMU. The model developed is applied to a sub-watershed of the Yasu river basin in Shiga Prefecture, Japan, in order to demonstrate the model's ability to determine optimum allocation of discharged loads of total nitrogen from various LMUs in the sub-watershed.

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To evaluate the effect of irrigation activities on watershed hydrologic cycle is one of the recent issues, and a runoff model is essential for this purpose. The basic structure of the grid-based distributed hydrological model was examined with the aim of the development of a model which can evaluate the effect of irrigation activities. This model called Kinu-Kokai model includes horizontal flow (i.e. surface flow, interflow, groundwater flow, channel flow, and inflow into channel), vertical flow (i. e. precipitation, evapotranspiration, snowcover/snowmelt, infiltration, and percolation), and artificial flow (i.e. artificial intake). The result shows that simulated hydrographs at gauge stations adequately coincided with observed ones. However, matching of observed and simulated groundwater hydrographs weren't good. It was implied that this poor result originated from not only the handling of the rainfall but also the structural problem of the grid-based distributed hydrological model.

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This study was conducted to clarify soil moisture behavior and consumptive characteristics of sloping upland reclaimed a few years ago. Observation sites were located at higher or lower location in sloping upland field.
Planting crops were radish and red turnip in 1992 autumn season, pumpkin and corn in 1993 spring season.
The results obtained are as follows: In the upland reclaimed a few years ago, even in the same field, there were significant differences of soil classification, physical property and water retentivity between observation sites. From the topographic and meteorological factors in the sloping upland, soil moisture situation had been assumed to be drier in higher location, but practical situations were different or not so clear without corn in 1993. However, soil moisture consumptive use was to be larger, but soil moisture extraction of shallow layer was almost tended to be larger in lower location than higher location.
Soil moisture behavior and consumption in the sloping upland were considered to depend on soil properties and differences of evapotranspiration, furthermore, runoff and storage in furrow by precipitation and soil moisture movement in the soil layer.

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In the melt season, most snowmelt phenomenon occurs at the surface of the snowpack, and meltwater percolates to the ground surface with time lag. To forecast snowmelt runoff, it is necessary to understand the mechanism of meltwater percolation in snow cover.
In this study, meltwater amount arrived at the ground and meteorological factors were observed, and meltwater amount generated at the surface estimated by applying the heat balance method, were compared with meltwater observed at the ground. Then, it was clarified that there was a time lag between generated at the surface and arrived at the ground. In addition, using the percolation model, proposed for arctic snow cover or glacial area, meltwater at the ground was estimated from meltwater generated at the surface. As a result, preferable reproducibility could be achieved for the time after the peak time of the graph. On the other hand, it was clear that amount of loss caused by neglecting fluxes which formed shock front, was 19% of meltwater at the surface on an average.

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