2002 Fiscal Year Final Research Report Summary
Study on initial process of soil erosion, on sloped, cropland in humid tropics using soil water-monitoring system
| Project/Area Number |
12460032
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
FUNAKAWA Shinya Kyoto University, Graduate School of Agriculture, Assistant Professor, 農学研究科, 助教授 (20244577)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Sota Kochi University, Faculty of Agriculture, Assistant, 農学部, 助手 (10304669)
HIRAI Hideaki Utsunomiya University, Faculty of Agriculture, Assistant Professor, 農学部, 助教授 (20208804)
TANAKA Ueru Kyoto University, Graduate School of Global Environmental Studies, Assistant Professor, 地球環境学堂, 助教授 (10231408)
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| Project Period (FY) |
2000 – 2002
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| Keywords | capillary saturation / condition for surface runoff generation / datalogger / Internal drainage in soil profile / monitoring for soil water dynamics / monsoon climate / rainfall intensity / volumetric soil moisture content |
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| Research Abstract |
The condition and process of runoff generation were studied quantitatively by a water dynamics-monitoring system Three experimental plots were installed on sloped agricultural field in northern or northeastern Thailand under monsoon climate. The amount of rainfall, volumetric soil moisture content, and the amount of surface runoff were continuously monitored for every 10 minutes using a datalogger, which was installed in a small-scale field plot (1m × 1m or 25m × 2.5 m). Then the fate of water derived firm rainfall was divided into three destinations, i.e. increment of soil moisture, surface runoff and water loss. Based on these data, the rate of water loss and surface runoff and the initial conditions for their generation were determined as functions of rainfall intensity, initial soil moisture content, etc. The results obtained are summarized below :
1) Both the rate of water loss and surface runoff were strongly dependent on rainfall intensity ; and also on initial moisture content of the surface soil to some degree
2) In early stage of rainy season, water delved firm rainfall is largely lost through evapotranspiration, and partially accumulated into the soil as capillary water : As a result, gradual increment of soil water throughout rainy season is observed especially in medium to the fine textured soils
3) In late rainy season, a water loss through internal drainage increased
4) Different distribution patterns for rainfall intensity and soil moisture condition during rainy season were observed among the experimental plots, resulting in following types of runoff generation risks :
i) rainfall intensity-dependent risk in low elevation area in northeastem Thailand
ii) capillary saturation-enhanced risk in medium elevation area in northern Thailand
iii) risk by increased rainfall intensity in later rainy season in highland in northern Thailand
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[Publications] Funakawa, S., Kosaki, T.: "Desertification in the Aral area, Handbook for global Environment (2nd edition), (Eds. Fuwa, K., Morita, M.,)(Tokyo, Japan)"Asakura-shoten. 1129(708-717) (2002)
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