| Budget Amount *help |
¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2013: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2012: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2011: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
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| Research Abstract |
The objective of this study is to evaluate the impacts of the agricultural water use restructuring project on the physical and chemical water properties of the oxbow lake in Hokkaido, Japan. We predicted that decreased water removal after the pumping station was abolished would increase TN concentrations in the lake water. Though removal of water by pumping tends to take pollution from the lake, TN concentrations fell after pumping station was abolished. The cause of decreased TN concentration was mainly decreased organic nitrogen concentration. Moreover, the TN load balance changed from an outflow type to a storage type in 2011 and 2013 despite decreased input load into the lake.
We suggest that this reduction in TN concentration after 2011 reflects the decreased organic nitrogen concentration due to biological purification effects. This is because increasing retention time caused load removal from the lake, and the water retention time also increased significantly in this lake.
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