• Journal of Wetlands Research
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• v.15 no.1
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• pp.149-157
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• 2013

The weirs built so far are mainly overflow type weirs overflowing to the upstream. Main advantages of overflow type weirs are, effective water resources management and easy design, construction and maintenance due to many accumulated studies. However, due to the special feature of the overflow type weir where water overflows through the upstream of the weir, the silt coming from the upstream is not discharged to the downstream of the weir. This increases the river bed and reduces the reservoir capacity, and as a result, the weir loses its function. A underflow type weir with a water gate has been implemented in order to solve such sediment deposit and weir maintenance problems. However due to the design problem of recently constructed underflow type weirs, the river bed of the downstream of a weir has been scoured. And this leds to a structural problem. In this study, the flow characteristics of overflow type weirs and underflow type weir, hydraulic jump length analysis depending on change of water depth and the amount of specific energy loss generated per unit length depending on a weir type have been compared and analyzed, for the effective design and management of the weirs. The experiment results show that, when identical upstream conditions of underflow type weir and an overflow type weir were maintained, the hydraulic jump length was up to twice longer with Fr(Froude number) 3.5 of the hydraulic jump length at the underflow type weir, and the hydraulic jump length gradually decreased as the downstream water depth increased. The comparative analysis result of the amount of specific energy loss generated per unit length showed that the amount of energy loss per unit length was twice higher for an overlfow type weir than a underflow type weir. Therefore, in case of a underflow type facility, an additional energy reduction facility is determined to be necessary for safety of water construction structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.617-625
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• 2016

The objective of this study was to evaluate the groundwater drawdown and streamflow depletion due to each groundwater pumping from 110 wells located near stream using the Hunt's analytical solution (1999). The calculated results revealed that the streamflow depletion rate divided by the pumping rate for each well location mostly exceeded about 80% of pumping rate on average for 5 years. The results also showed that the stream boundary condition has made the influence distance shorter and the drawdown distribution skewed except for the streambed hydraulic conductivity and the stream bed factor (SBF) lower than $1.0{\times}10^{-9}m/s$ and 1.0, respectively. It was found that the groundwater pumping has significant impacts on the stream depletion showing above 80 % of stream depletion rate when the streambed hydraulic conductivity is higher than $1.0{\times}10^{-7}m/s$ and the stream depletion factor(SDF) is lower than 100. However, for other conditions, the SDF is not sufficient to be used as a criterion for determining whether the pumping has great impacts on stream depletion or not. Furthermore, the variation of the streambed hydraulic conductance has little change in stream depletion rate for the condition that the stream width is greater than 400 m.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.761-772
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• 2008

The object of this study is to develop the model that solves the numerically difficult problems in hydraulic engineering and to demonstrate the applicability of this model by means of various test examples, such as, verification in the gradually varied unsteady condition, three steady flow problems with the change of bottom slope with exact solution, and frictional bed with analytical solution. The governing equation of this model is the integral form of the Saint-Venant equation satisfying the conservation laws, and finite volume method with the Riemann solver is used. The evaluation of the mass and momentum flux with the HLL Riemann approximate solver is executed. MUSCL-Hancock scheme is used to achieve the second order accuracy in space and time. This study introduce the new and simple technique to discretize the source terms of gravity and hydrostatic pressure force due to longitudinal width variation for the balance of quantity between nonlinear flux and source terms. The results show that the developed model's implementation is accurate, robust and highly stable in various flow conditions with source terms, and this model is reliable for one-dimensional applications in hydraulic engineering.