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Quantitative Analysis of Groundwater Effluent and Reservoir-Water Influent in a Small Pond Using <sup>222</sup>Rn- and Water-Balance Equations

Japan Agricultural Research Quarterly
NII recode ID (NCID)
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Percolation of water from a pond may cause a landslide in a hilled rural area. Before measures to prevent such landslides can be planned, it is essential to identify reservoir-water influent from the pond. We describe an analytical method that uses 222Rn- and water-balance equations to quantify groundwater effluent and reservoir-water influent simultaneously, which is impossible using the conventional method that measures only surface-water inflow and outflow. We selected F pond, Nagano Prefecture, as the study site. We estimated the rate of 222Rn dispersion to the atmosphere by assuming a stagnant film between water and air with thickness inversely proportional to the rate of dispersion. By a laboratory experiment, we estimated the film to be about 830 ?m thick and found that the film thickness was not influenced by wind velocities less than 1.5 m s-1. A preliminary investigation suggested that reservoir-water was mixed very well. The groundwater effluent and the reservoir-water influent during the investigation were calculated to be 0.67 × 10-3 m3 s-1 and 0.41 × 10-3 m3 s-1 respectively, by making 222Rn- and water-balance equations and solving them. This analytical method is expected to be useful for not only prevention of a landslide but also for effective use of water and prediction of water quality.

Date of issued2004-10-01
CreatorHAMADA HiromasaKISHI Satoru

stagnant film


PublisherJapan International Research Center for Agricultural Sciences
NII resource type vocabularyJournal Article
RightsJapan International Research Center for Agricultural Sciences