Integrated field- and model-based study of hydro-environmental aspects of a small, endangered wetland in eastern Hokkaido, Japan |
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| Authors: | Takeo Tsuchihara Satoshi Ishida Masayuki Imaizumi Toshihiko Kawachi |
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| Institution: | (1) National Institute for Rural Engineering, Tsukuba, Ibaraki, Japan;(2) Graduate School of Agricultural Science, Kyoto University, Kyoto, Japan |
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| Abstract: | The hydro-environmental aspects of a small, endangered wetland (Totsuru wetland), located in eastern Hokkaido, Japan, are investigated, and the efficacy of a proposed engineering strategy for restoring the wetland is examined. Taking 222Rn as a target tracer and building a static 222Rn mass balance equation, the share of groundwater-genetic surface water in yielding the entire surface water in the wetland is appraised. The share is also appraised by using a different approach based on a non-static, site-specific water balance model. Both approaches yielded nearly the same percentage share, and therefore, it is concluded that 70% or more of the surface water entering the Totsuru swamp through the natural rivers is groundwater genetic. Using the water balance model, it is deduced that the reverse flow from the Uenbetsu drainage river is not less than 30% of the entire surface water flow entering the swamp, and therefore contributes considerably to mitigating the shrinkage of the swamp. Finally, through numerical experiments, it is shown that raising the water level of the Uenbetsu drainage river with a constructed weir to enhance the reverse flow is efficacious for restoring the wetland. |
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| Keywords: | Wetland restoration Hydrology Groundwater Radon Constructed drainage river |
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