17:15 〜 19:15
[AHW23-P05] Rainfall-runoff process in a Tropical Headwater Catchment, Malaysia
It is important to understand the rainfall-runoff process in the forest headwater catchments from the perspective of flood prediction and water resource supply to downstream areas, especially in the humid tropical regions, where heavy rainfall, especially during the rainy season, significantly influences Rainfall-runoff dynamics. However, there are few studies based on field observation in humid tropical regions. Therefore, in this study, we focused on the Rainfall-runoff process in humid tropical headwater catchment, including the role of subsurface water.
We conducted field observations in a headwater of the Ayer Hitam Forest Reserve in Puchong, Selangor in Malaysia. In this study area, stream water level and soil water pressure heads at the depths of 20 cm and 50 cm have been monitored since January 2025. In addition, we also collected stream water, precipitation, and spring water once a week.
The runoff responded promptly to the rainfall, and the runoff peak occurred at almost the same timing of the peak rainfall throughout the observation period. Also, the soil water pressure heads at 20 cm and 50 cm depths near the stream quickly increased in response to the rainfall and showed rapid decrease after the rainfall finished. The hydraulic heads at both depths were higher than that of stream water. So, hydraulic gradients from subsurface water toward the stream water should occur during the rainfall and during the rainless periods. These characteristics in hydraulic head suggest that subsurface water near the stream discharges to the stream water during both rainfall and rainless periods. Therefore, the importance of the contribution of subsurface water, such as soil and groundwater, was also shown in the rainfall runoff process in the headwater catchment in humid tropical regions.
We conducted field observations in a headwater of the Ayer Hitam Forest Reserve in Puchong, Selangor in Malaysia. In this study area, stream water level and soil water pressure heads at the depths of 20 cm and 50 cm have been monitored since January 2025. In addition, we also collected stream water, precipitation, and spring water once a week.
The runoff responded promptly to the rainfall, and the runoff peak occurred at almost the same timing of the peak rainfall throughout the observation period. Also, the soil water pressure heads at 20 cm and 50 cm depths near the stream quickly increased in response to the rainfall and showed rapid decrease after the rainfall finished. The hydraulic heads at both depths were higher than that of stream water. So, hydraulic gradients from subsurface water toward the stream water should occur during the rainfall and during the rainless periods. These characteristics in hydraulic head suggest that subsurface water near the stream discharges to the stream water during both rainfall and rainless periods. Therefore, the importance of the contribution of subsurface water, such as soil and groundwater, was also shown in the rainfall runoff process in the headwater catchment in humid tropical regions.