Establishment of the evaluation method of trade-off among various environmental aspects in the improving countermeasures of water environment

点击翻译按钮获取中文摘要

Benefit of water environmental improvement of Lake Suwa was evaluated to be 730 million Yen per year by Contingent Valuation Method. On the other hand, the damage of secondary environmental loads, such as CO2 generated was 23 million Yen. This comparison justifies the water improvement of this lake. Choice experiments showed that people give low value to protection of wildlife, and the water environmental improvement was esteemed be higher than mortal risk reduction. The analysis or human activities showed that the nitrogen load to Lake Suwa was reduced by half in the past 30 years. Frequent survey of water quality revealed that non-point source like the cropland generates high loading with rainfall. This shows that prevention of soil erosion is effective method to reduce nutrient loading to this lake. The correlation between concentration of PAHs in roadside and amount of traffic was analyzed. The risk of chemical substances in the ecosystem and drinking water in Hiroshima Bay was evaluated. The relation between the amount of loading from the basin, and the amount of deposition in the lake was analyzed for poly aromatic hydrocarbon and butyl tin. These two were comparatively well in agreement. In Lake Suwa, outbreak of algal bloom decreased in recent years and the amount of existing of mosquito fell remarkably. Moreover, it turns out that reduction of a fish catch is being enhanced with a peak of the 1970s which were the severest as for contamination. Although water quality improvement progressed by construction of a sewer in Lake Suwa, the percentage of contribution of the load from non-point source increased.