Seasonal fluctuation of groundwater in an evergreen forest, central Cambodia: experiments and two-dimensional numerical analysis |
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| Authors: | Makoto Araki Akira Shimizu Naoki Kabeya Tatsuhiko Nobuhiro Eriko Ito Yasuhiro Ohnuki Koji Tamai Jumpei Toriyama Bora Tith Sopheavuth Pol Sopheap Lim Saret Khorn |
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| Institution: | (1) Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba Ibaraki, 305-8687, Japan;(2) Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan;(3) Kyushu Research Center, Forestry and Forest Products Research Institute, Kumamoto 860-0862, Japan;(4) Forest Wildlife Science Research Institute, Forestry Administration, # 40 Preah Norodom Blvd, Phnom Penh, Cambodia |
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| Abstract: | This study of a water cycle was conducted in an evergreen forest located in the Mekong River Basin in central Cambodia. At
the observation site, we measured the dynamics of the spatial distribution of groundwater levels. The groundwater movement
was analyzed two-dimensionally using boundary conditions and parameters that had been observed in the field. The climate in
the research area is dominated by two seasons, which occur annually: a rainy and a dry season. The groundwater levels are
generally high during the rainy season and low during the dry season. Groundwater levels were measured along a stream, which
flowed through the study site. The streambed was visible at the head of the stream in January. At the next downriver well
point, the streambed appeared in March. Finally, it became visible at all well points in April, meaning that surface runoff
had disappeared temporarily and instead flowed underground during the ensuing dry period. Groundwater levels of the studied
lateral flow perpendicular to the stream that seeped and infiltrated into the stream were 1.2–2.5 m deep (in April), which
was the lowest level recorded for the year. During that period, the depth of the groundwater of the studied lateral flow fell
by as much as 56 mm per month. In addition, the lateral flow groundwater infiltrated into groundwater of the stream during
that period. The groundwater level fluctuation was estimated based on a two-dimensional analysis of lateral flow perpendicular
to the stream using a numerical simulation model with soil physical parameters and observed boundary conditions. The observations
of ground water fluctuations were well reproduced. Deep seepage of groundwater was estimated using a uniform boundary condition
that allowed efflux through the bottom, estimated as being approximately 30 mm per year. The simulated deep seepage rate was
considered plausible considering other hydrological components such as soil water storage fluctuation. |
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| Keywords: | Groundwater Numerical analysis Forest soil Water cycle Dry evergreen forest Cambodia |
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