Katsushige Shiraki, Nobuaki Tanaka, Tantasirin Chatchai, Masakazu Suzuki
Received 2017/03/03, Accepted 2017/04/30, Published 2017/07/11

Katsushige Shiraki1), Nobuaki Tanaka2), Tantasirin Chatchai3), Masakazu Suzuki4)

1) Graduate School of Tokyo University of Agriculture and Technology
2) University Forest in Aichi, Graduate School of Agricultural and Life Sciences, The University of Tokyo
3) Faculty of Forestry, Kasetsart University, Thailand
4) Former Graduate School of Agricultural and Life Sciences, The University of Tokyo

The water budget and discharge processes in a seasonal tropical watershed were analyzed. The watershed has very stable base stream flows even in the late dry season and very quick direct runoff during rains. A tentative runoff error correction method applying an existing lumped runoff model was proposed in this paper and showed good agreement with the correct runoff error. After correcting runoff data, the annual average rainfall and runoff during the 11 years of 1998–2008 were calculated respectively as 1870.4 mm and 1229.2 mm. The average annual water loss was 641.2 mm. Distribution measurements of topsoil depth taken using a knocking cone penetration meter showed that this watershed has a deep topsoil layer (5.3 m average). Groundwater tables are apparent only in the lower area of the watershed. A saturated swamp area is a permanent feature near the weir. Results suggest that the stable base flow in this watershed was generated by return flow of soil-water infiltration into the thick topsoil and fractured bedrock.

[Full Text]

Copyright (c) 2017 The Author(s) CC-BY 4.0