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A model analysis for nonpoint pollutant reduction in paddy field watersheds

稻田流域面源污染物减排模型分析

基本信息

批准号：
12660221
负责人：
TAKEDA Ikuo
金额：
$ 2.11万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2003
项目状态：
已结题

项目摘要

Investigations on water quality and hydrology were conducted in a paddy field and forest watersheds and essential factors, which can be useful for establishing a water purification model, were extracted. In the forest watershed, runoff volume was about 1 mm/d during non rainy days, whereas it declined to be 0.5 mm/d during draught seasons. However, runoff showed relatively sharp increase during rainy days and decreased to be about 1 mm/d rapidly. The ration of runoff to the amount of rainfall was about 30 %, indicating that about 70 % of rainfall amount was evapotranspiration. Then the reliability of this phenomenon was discussed. Furthermore, pollution loads from the investigation sites were quantified. In the paddy field watershed with a circular irrigation system, the concentrations of nitrogen, phosphorus and COD in the Hii River were lower than those in other sites of drainage rivers. The concentrations of phosphorus and COD tended to decrease with the river flowing whereas that of nitrogen did not show such decreasing trend. On the other hand, the concentration of DO in the Hii River was the highest and oxygen in the river can contribute decomposition of organic matters. There was not clear relationship between concentration decrease with the river flowing and amounts of rainfall of total nitrogen, total phosphorus and COD. The concentration decrease was caused by precipitation in drainage rivers and retention ponds and aerobic decomposition. The amounts of removed pollutants tended to increase with increasing hydraulic retention time with a few exceptions.

对水田和森林流域进行了水质和水文调查，提取了可用于建立水净化模型的要素。在森林流域，非雨季的径流量约为1 mm/d，而在干旱季节则下降到0.5 mm/d。降雨期径流量增加幅度较大，并迅速减少至1 mm/d左右。径流与降雨量的比例约为30%，表明蒸散发约占降雨量的70%。然后讨论了这种现象的可靠性。此外，还对调查地点的污染负荷进行了量化。循环水灌溉水田小流域中，Hii河的氮、磷、COD浓度低于其他流域。随着河流的流动，磷和COD的浓度呈下降趋势，而氮的浓度则没有下降趋势。另一方面，Hii河的DO浓度最高，河流中的氧有助于有机物的分解。总氮、总磷、总COD浓度的下降与河流流量和降雨量之间关系不明显。浓度下降主要是由流域河流和截留池的降水和好氧分解引起的。除少数例外情况外，去除污染物的量随水力滞留时间的增加而增加。