Mariko Saito, Maki Tsujimura, Siti Nurhidayu Abu Bakar
Received 2022/11/04, Accepted 2023/02/24, Published 2023/05/10

Mariko Saito¹⁾, Maki Tsujimura²⁾, Siti Nurhidayu Abu Bakar³⁾

1) Graduate School of Science and Technology, University of Tsukuba, Japan
2) Faculty of Life and Environmental Sciences, University of Tsukuba, Japan
3) Faculty of Forestry and Environment, Universiti Putra Malaysia, Malaysia

This study aims to clarify the contributions of pre-event water to storm runoff using environmental tracers (dissolved inorganic ions and stable isotopes) in a tropical forested catchment in Puchong, Selangor, Malaysia. We performed intensive sampling campaigns of stream water and throughfall for two storm events in July and November 2018. The discharge showed a low peak of 0.13 mm/h in event 1, with 18 mm of total rainfall, whereas event 2, with 50 mm of total rainfall, showed a quick discharge peak of 1.17 mm/h and a slow recovery of 0.39 mm/h. The nitrate concentration in the stream water during event 2 was higher than that in event 1. The temporal variations in nitrate ions indicate that subsurface water provided a dominant stormflow in event 2. Hydrograph separations using silicate as a tracer revealed that pre-event water was the dominant component of the storm hydrograph (58–98%). Our results suggest that pre-event water plays an essential role in storm runoff of headwaters in humid tropical regions.

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