The appearance of cattle grazing abandoned paddy fields can be used to evaluate attitudes towards this land-use change. The semantic differential (SD) method was used families of a university student to evaluate and compare attitudes towards five types of rural landscape: pasture, pasture grazed by cattle, rice paddy field, abandoned paddy field converted to pasture and abandoned paddy field converted to pasture grazed by cattle. Cattle grazing abandoned paddy fields were determined to have a positive effect on the landscape. However, all grazing cattle created a negative attitude because of the unclean appearance of the landscape. Grazing cattle at high stocking rates in small areas could create a negative attitude because of the oppressive appearance of the landscape. The acceptance of grazing cattle was lower if the animals ware newly introduced to the landscape.

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We investigated the water budget and outflow characteristics of total phosphorous (T-P) and total nitrogen (T-N) of an irrigated paddy field on an Andisol in the cool-temperate zone area. Total effluent flux of water from the paddy field during one cropping period was 2192 mm, 1490 mm (ca. 70%) of which flowed out through the downward percolation. The net discharge of T-P and T-N from the paddy field during one cropping period was 0.47 kg/ha and 35.9 kg/ha, respectively, most of which flowed out through downward percolation. Amounts of T-P and T-N discharged through sublayer soil to the ground water with the downward water percolation corresponded to 23% and 80% of those leached out from the plow layer soil, respectively.

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We set experimental circumstances controlled by aquatic plant mowing in the preserved pond, Komaba-Kita district. Aquatic plant mowing for a space of the pond had not been performed for over two years. For other space of the pond, eco-friendly type of aquatic plant mowing had been performed twice a year usually. There were many of small and medium scales of aquatic plant communities and only one large scale of aquatic plant community in the pond. Then we investigated characteristics of nest sites of the ninespine stickleback in the pond. We found total number of 20 nests. Almost all of those nests occurred at rim of these communities, whereas there were not any nests in central parts of medium and large scale of the communities. It was suggested that nest sites would concern deeply with aquatic plant mowing. To establish many of small and medium scales of aquatic plant communities owing to eco-friendly type of aquatic plant mowing appeared to increase a lot of rim of plant communities, indicating leading to increase in extent of rim areas of the suitable site for nesting.

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We investigated that the cadmium concentrations, the growth and the yields of the rice plants by using two models of stratified paddy fields during three years. The first model had water flow in an open system at the plowsol(length:10.0cm) became oxidation layers. The other model had water flow in a closed system at the plowsol became reduction layer. The plow layer(length:12.5cm) made of soil dressing that did not polluted soil. But the plowsol in those models was made of polluted soil (3.39mg/kg) that existed in polluted paddy field.
As a result, the range of cadmium concentration in both models in brown rice, stems and leaves was 0.000-0.2000mg/kg, 0.050-0.845mg/kg, respectively. Also the one in roots in the plow layers and that in the plowsoles were 1.760-4.440 mg/kg, 5.170-12.73mg/kg, respectively. Cadmium concentration in every item with water flow in an open system became higher than that with water flow in a closed system. We realized that percolation patterns did not influence the growth of rice plants. But the number of panicles and the weight of the brown rice with water flow in the closed system became higher than those with the water flow in the open system.
Above those result, it was clear that percolation pattern influence on the concentration of cadmium in the rice plant, the growth and the yields under inundation during the cultivation with stratified models that have soil dressing.

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The purpose of this research is to evaluate snow storage depth from the accumulated snow in Tedori River Basin by the difference between the observed discharge of the river at the melting period and the estimated discharge of which there was no accumulated snow by using the tank model, and which could be done without using the accumulate snow survey. As a result of three years of analysis from June '76 to May '79 before Tetori Dam construction in this basin, the snow storage depth was estimated as 462mm to 1,179mm, which greatly contribute to the paddy irrigation at early spring. Moreover, the discharge was sometimes shows under water right of irrigation period if the snow resources was not expected.

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While the “Paddy Field Dam” project has been recognized as an effective flood control measure, there are some cases in which the runoff control boards are vertically installed on the opening of the drainage boxes without careful consideration of the orifice shape and size. The important criteria for the runoff control boards to be satisfied are: 1. to maintain a sufficient peak runoff control function, 2. to avoid excessive ponding causing overflow, 3. to minimize the influence to the ordinary water management, and 4. to reserve sufficient orifice area to avoid blockage of the orifice with floating litters. The purpose of this study is to examine proper shapes and sizes of the orifice to satisfy the criteria for the vertically installed runoff control boards through experiments and simulations. Given the condition that the orifice has sufficient area to avoid overflow with 10 and 20 year return period rainfall event (criteria 2), the simulation results show that the orifice with horizontally wider shapes has advantages over the square or circular shapes in terms of the criteria 1 and 3. The disadvantage of the horizontally wider shapes is the blockage of the orifice with floating litters (criteria 4). In conclusion, we proposed to secure sufficient vertical distance to avoid this problem by setting a lower limit on the vertical distance and then determine the widest horizontal distance to optimize all the criteria. In addition, we have constructed the “Orifice Design Assist Tool” on the basis of the examinations in this study.

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A GIS based model developed by the authors are applied for selecting suitable rice cultivation area in inland valleys that has high potential for rice production in West Africa where rice consumption is increasing very rapidly. The model has the following features. 1) The model is to evaluate the suitability of the land for lowland rice based on score distribution maps respectively made by the data of 29 evaluation parameters. 2) The parameters are classified into 4 categories; bio-physical, technical, socio-economic and health-environmental parameters. 3) Each scored map (layer) is integrated to obtain total scores by multiplying a weight which is determined by the importance of parameters. The suitability for rice in two study sites was evaluated using the model. Mankran and Jolo-Kwaha watershed selected as the study sites from different agro-ecological zone in Ghana. Applying the data of 12 parameters acquired in the study sites to the model, “very suitable” or “suitable” occupies around 30% in Mankran study site and around 60% in Jolo-Kwaha study site.

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