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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 18 (2010), Paper 9 Posted May 26, 2010 GIS-BASED WATERSHED ANALYSIS AND SURFACE RUN-OFF ESTIMATION USING CURVE NUMBER (CN) VALUE
Henry A. Adornado ABSTRACT A study was conducted in the Calabarzon Region, Philippines, to determine the natural boundary and extent of watershed areas as well as the amount of run-off they can generate. Geospatial processes determined the natural boundary by following the highest ridge dividing each watershed and showed that the basin in this part of the region has a total area of around 93,000 ha and consists of three catchments/watersheds. The Kaliwa watershed occupies the largest area, 50.7% of the total, followed by Kanan watershed with 42.2%. The Agos river, the confluence of these two watersheds, flows down to the Polillo Strait and serves as the political boundary between the two municipalities. It has a catchment area of 7.1%. A curve number (CN) model showed the watersheds combined surface run-off is around 243 million cubic meters based on soil type, landcover and 30-year precipitation data. The Kaliwa watershed occupies the largest area and is capable of generating the highest surface run-off, followed by the Kanan watershed and Agos river catchment with 119 M, 108 M and 16 M cubic meters, respectively. The quality of soil and high precipitation results in a high amount of run-off. These findings are significant to the community living in and around the area and can be used by managers for decision and policy making. Reference: Adornado, H.A., and M. Yoshida. 2010. GIS-based watershed analysis and surface run-off estimation using Curve Number (CN) value. Journal of Environmental Hydrology, Vol. 18, Paper 9. CONTACT: Henry A. Adornado Department of Bioresource Science College of Agriculture Ibaraki University 3-21-1 Ami Chuo, Ami-Inashiki Ibaraki ken 300-0393 Japan E-mail: hadornado@mx.ibaraki.ac.jp |
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