Comparison of the difference of runoff characteristics for pollutant load between environmental and land-use conditions

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The water quality runoff characteristics were compared between the 4 farm village areas of Hokkaido, Kyushu, Honshu Pacific side and Honshu Sea of Japan side. The water quality runoff characteristics of each area were clarified by the monitoring results from each area. With regard to Honshu Pacific side, nitrogen and phosphorus loads were found at high concentrations because of the effect of pig production. It was pointed out that the nutrient loads could be accumulated in the soil and then flowed out. In addition, Tanno pond in Shizuoka Prefecture of Honshu as well, it was confirmed that nitrogen was found at high concentration by the influence of the excessive fertilizer. It was pointed out that this also could be the influence of the cumulative loads in the soil. With regard to the grass dairy watershed in Hokkaido, it was pointed out that the pollutant loads accumulated due to the snow were concentrated at the time of the melting of snow and they flowed out. In addition, the water quality purification characteristics by riparian trees were clarified. In the area on the Sea of Japan side, the repetition use of the irrigation water, which is characteristic of flat ground, is conducted and it was found that pollutants were purified by the operation. In Kyushu area, the characteristics of a water quality changes in Chikugo River basin were clarified. The result suggested that land use affected the changes in water quality. That is, the water quality runoff characteristics in each area were clarified by this year's research. Especially, it was confirmed that conditions of land use largely affected the changes in water quality. The diversity of water quality runoff characteristics among farm village areas could be understood. In the future, integration of the knowledge of the countermeasures for diffuse source pollution is expected. It can be considered that the research on the countermeasure for diffuse source pollution was developed greatly.