2010 Fiscal Year Final Research Report
The effect of agriculture on water environment in a subtropical island
| Project/Area Number |
20780179
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Irrigation, drainage and rural engineering/Rural planning
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| Research Institution | National Agricultural Research Organization |
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Principal Investigator |
YOSHINAGA Ikuo National Agricultural Research Organization, 農村工学研究所・企画管理部・業務推進室, 企画チーム長 (50414420)
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| Project Period (FY) |
2008 – 2010
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| Keywords | 水質汚濁 / 水環境 |
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| Research Abstract |
The purpose of this study was to analyze the effect of agriculture on water environment in a water-starved subtropical island. Most irrigation ponds were categorized as in eutrophic states and water blooms were observed. It is suggested that runoff from livestock is the main nutrient source. Rainfall runoff from farmland had few eutrophying effects on inflowing loads, because the runoff mainly consisted of roadway discharge and so relevant concentrations were low. Nitrate nitrogen concentrations of groundwater were high, assuming that the nitrate contamination originated from fertilizer and manure. The values and trends of nitrate concentrations at monitoring wells varied greatly. These results imply horizontal groundwater flow is not uniformly distributed and the each well gathers water from vicinal area. It was estimated that around 22% nitrogen output from human activity leached to the groundwater.
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