Comparison of runoff characteristics of two adjacent basins in a tropical rainforest using a modified hydrologic cycle model with outflow

Abstract

Abstract:We propose a new runoff model including an outflow process that was applied to two adjacent basins (CL, TL) located in Lambir Hills National Park in north-central Sarawak, Malaysia. Rainfall, runoff, topography, and soil layer thickness were observed. About 19% of annual runoff was observed in the CL basin (21.97 ha), whereas about 46% was observed in the TL basin (23.25 ha). It was inferred that the CL basin has an outflow because of low base flow, small runoff peak, and excessive water loss. By incorporating the outflow process into the HYdrological CYcle MODEL, good agreement between the data generated by the model and that observed was shown, with the exception of the data from the rainless period. Then, the fitting parameters for each basin were exchanged, except for the outflow parameter, and the characteristics of each basin were compared by calculating virtual runoff. As a result, the low base flow of the CL basin was estimated by the movement of the rainwater that escaped from the basin as deep percolation or lateral flow (11% of rainfall). The potential of the CL basin for mitigating flood and drought appeared to be higher than that of the TL basin. This is consistent with the topographic characteristics of the CL basin, which has a gentler slope than the TL basin.

Effects of bedrock groundwater dynamics on runoff generation: a case study on granodiorite headwater catchments, western Tanzawa Mountains, Japan

“…In this study, we used the HYCY model (Fukushima, 1988) by incorporating the outflow factor proposed by Wakahara et al (2014) to estimate outflow such as groundwater flow into bedrock or other watersheds. The outflow component representing the bedrock groundwater infiltration was attached to the base flow tank and was calculated by multiplying the outflow ratio and the base flow rate under the assumption that bedrock infiltration mainly occurs through the stream bed.…”

“…They observed that the base flow rate could be determined by groundwater flow through bedrock and inter-catchment groundwater transfer in second-and third-order catchments. Further, Wakahara et al (2014) modified the hydrological cycle (HYCY) model (Fukushima, 1988) to quantify outflow from catchments in the form of deep infiltration or lateral flow and demonstrated that low base flow was caused by outflow escaping from the basin. Kosugi et al (2006) directly measured bedrock infiltration.…”