A number of factors are being constrained the proper development and utilization of groundwater in the Comilla region, Bangladesh. Lowering water table beyond suction limit in the upper aquifer, improper pump-well matching, inaccurate estimation of aquifer recharge and unavailability of aquifer management strategy are some of the constraints. Therefore, field studies on groundwater development were carried out and thereafter groundwater flow and solute transport simulation are done. A two-dimensional finite difference flow model with the superimposed solute transport calculated by the Method of Characteristics (MOC) is used for simulation purpose. Out of the upper unconfined, the main semi-confined and the lower semi-confined aquifers in the region, the main aquifer is modeled by MOC. The annual climate is modeled as a wet recharging period (April to September) and a dry discharging period (October to March). In model calibration, the near-to-optimum values of boundary and initial conditions are found by trial and error which are used for transient flow and solute transport simulation. Transient flow model shows the detailed head distributions and flow pattern of the region. The model estimated recharge is found to be 132 mm, although the atmospheric recharge into the upper aquifer is much higher. The solute transport is only modeled as hypothetical examples. No perceptible movement of the plume is detected during the simulation period. A risk of the main aquifer contamination is low, but the long-term effect must be taken into account.

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Irrigation canals and rivers require matching with the surrounding natural scenes and giving careful consideration to their water environments. Though many concrete blocks with stones are developed for this purpose, the hydraulic characteristics of those blocks are not well known. In this study, the roughness coefficients of concrete block with pebbles are examined by measuring water depths in a laboratory rectangular channel. The values of the Manning's roughness coefficient are estimated by numerical integration of the non-uniform flow equation. Changing discharge, channel slope, and water depth at the downstream end, 45 experimental runs are conducted. The estimated Manning's roughness coefficient has a good correlation with Reynolds number and ranges from 0.0135 to 0.0425.

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This is a research paper on the development of the water resources of Ojika isolated island adjacent to Nozaki island located in Nagasaki prefecture. Nozaki island is a small island having an area of 7km^2, and the mountain has a steep altitude ranging from 240m to 350 m. The rainfall concentrates only during the typhoon and in the rainy season. Moreover, considering the fact that there exists a National Park, it is necessary to construct an intake of water so that it insures to obtain most water from the smallest torrent intake works. Further more, care is to be taken to avoid the mixing of dead leaves and sand with water. Therefore, the intake method for water discharge, the trap-dam and the planning of water utilization etc. should be properly designed which acts as the primary factors of planning of the project. So, it is considered that the planned research will be a standard design for ensuring good water resources in a small island like the Nozaki isolated island.

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This paper is a study on structures of intake works of an isolated island where it is rainy, the topography is steep and the valley is deep. After investigating the structures of the existing intake works, the topography and the streams of Yaku Island in Kagoshima prefecture, the problems of these intake works are made clear. And intake works are designed and constructed, which are fit for the rainy and steep place. Then the utilization of rainfall on the isolated island is analyzed. And, a new multipurpose construction combining a debris barrier with a torrent work is exploited to prevent debris flows and to take water at the same time.

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This study is conducted to determine the potential of digital images in turbidity measurement. To do this, image data of turbid water is obtained using a digital camera in the laboratory, and the possibility of the qualitative analysis of turbidity using imaging control software is examined. The experiments reveal a relationship between the average image brightness of a digital image, obtained by special software technique, and the turbidity measured by a turbidimeter. Photographs of a digital image are not affected directly or indirectly by the lighting conditions. The relationship between turbidity and the average image brightness is highly significant in 4 channels, GRAY, RED, GREEN and BLUE. However, BLUE is determined to be most suitable because of the large gradient of the regression line. This is proved by field data during a rainfall event.

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In this paper, the authors investigate the method of the use of electrolyzed rainwater. Well water and rainwater are electrolyzed in seven cases of pH values. Lactic acid calcium and sodium chloride are used as electrolytes when water is electrolyzed. Sodium chloride is added in the case of the well water. Water temperature, pH, electric conductivity, and oxidation-reduction potential (ORP) are measured to examine change in water quality. The pH values of anode water indicate acidity, whereas those of cathode water indicate alkalinity. The ORP values of anode water increase during the first five hours and then level out. Those of cathode water decrease during the first one-hour and then increase. Quality of Cathode water changes easily both in pH and in ORP. Sodium chloride has more effect than lactic acid calcium.

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There are many studies concerning aeration in free falls such as weirs and spillways. In this experimental study, an overall coefficient of oxygen transfer at a weir is measured in various conditions of discharge and water temperature. From this experiment, it is obtained that the overall coefficient of oxygen transfer is proportional to the discharge under the 2.5L/s and increases with an increase in the water temperature. As the overall coefficient of oxygen transfer depends on the water temperature, a temperature correction coefficient for the overall coefficient of oxygen transfer is investigated.

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Instructions are given to prepare the manuscript of an English paper submitted to the Journal of Rainwater Catchment Systems. Being a model in itself, the document demonstratively prescribes the layout of the manuscript. Manuscripts should be typed on one side of white A4 size paper when they are submitted. Accepted manuscripts will be off-set printed. Titles of papers, names and affiliations of authors, abstracts, main texts, headings, references, equations, mathematical symbols, captions of figures and tables and so on should be in specified fonts. All references cited should be collected together at the end of the paper. Figures and Tables with their captions should be placed appropriately.

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Instructions are given to prepare the manuscript of a Japanese paper submitted to the Journal of Rainwater Catchment Systems. Being a model in itself, the document demonstratively prescribes the layout of the manuscript. Manuscripts should be typed on one side of white A4 size paper when they are submitted. Accepted manuscripts will be off-set printed. Titles of papers, names and affiliations of authors, abstracts, main texts, headings, references, equations, mathematical symbols, captions of figures and tables and so on should be in specified fonts. All references cited should be collected together at the end of the paper. Figures and Tables with their captions should be placed appropriately.

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