Rainfall and Runoff Observations in the Subtropical Forest of Okinawa Island, Japan


We set up two experimental catchments to provide an improved understanding of hydrological processes in a subtropical forested area in the northern part of Okinawa Island, Japan. We calculated runoff using water level data (recorded by a pressure-type water level gauge installed in a box culvert) and a discharge rating curve (derived from in situ observations). Water balance calculations for 2010 showed that the rainfall, runoff and evapotranspiration losses (= rainfall – runoff) were 3403.6 mm, 2285.7 mm and 1117.4 mm, respectively. This result was in agreement with previous results from other forested experimental catchments in this region. Direct runoff, as a proportion of event total rainfall, can be expressed by the empirical equation (Qdirect = 0.0048, Pevent 1.7971, R2 = 0.9599). When Pevent was 100 mm or less, the ratios of Qdirect to Pevent were less than 15% in general. When Pevent exceeded 100 mm, the ratios were 20% - 30%.

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Kabeya, N. , Shimizu, A. , Shimizu, T. , Ikuzawa, H. , Arakaki, T. , Furugen, H. , Ohnuki, Y. and Asano, S. (2014) Rainfall and Runoff Observations in the Subtropical Forest of Okinawa Island, Japan. Journal of Water Resource and Protection, 6, 625-634. doi: 10.4236/jwarp.2014.66061.

Conflicts of Interest

The authors declare no conflicts of interest.


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