• The Journal of Engineering Geology
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• v.28 no.4
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• pp.541-552
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• 2018

The implementation of drought measures in the upstream areas of river basins is seldom considered with respect to water supply. However, the demand for such measures is increasing rapidly owing to the occurrence of severe droughts, and interventions on streams and the water supply are needed. Physical interventions are an option to prevent streams from becoming dry and to maintain stream water flow, but dam construction is challenging because of environmental and ecological considerations. Here, a feasibility study was conducted to assess the potential effects of sand dams, which are widely used in arid regions in Africa. The SWAT-K model, which is a hydrologic model used for Korean watersheds, is used to estimate the flow rate of water in an ungauged watershed. The changes in water storage of the sand-dammed reservoir and in downstream flow rates are estimated for two types of sand dam (natural and dredged). The results show that sand dams are capable of increasing the downstream flow rate during normal conditions and of mitigating water supply problems caused by the withdrawal of water during drought periods.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.329-337
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• 2019

Bottled water companies in Korea are required to conduct an environmental impact assessment of their drinking water supply at least six months before the expiration of their five-year marketing and production license. The water level drawdown, production well water quality, and monitoring well observation results are the most important items that are evaluated in the assessment report. Here we evaluate the relationship between well drawdown and pumping capacity with pumping time from the production wells of bottled water manufacturers located in Cretaceous granite (site A) and Precambrian gneiss (site B). The method to reduce the pumping capacity is more effective in decreasing the drawdown than the method to simultaneously control the pumping and recovery times. Furthermore, the monitoring data from the pH monitoring sensors that were installed in Precambrian gneiss (site C) yield pH values that increase with time and eventually plateau at a certain value. We therefore propose that pH monitoring is either discontinued or improved to provide more reliable and usable results.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.163-172
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• 2011

To provide the operation rule curve for suppling instream flow to urban stream from reservoir, the Soho reservoir with watershed area of 7.4 $km^2$ and total water storage of 2.58 $Mm^3$ was planned at the headwaters of the Daejeoncheon. Daily streamflow was simulated and using the simulated streamflow and desired instream flow, the operation rule curve by Senga method was drawn and evaluated through reservoir operation. Senga method is derived by accumulating the differences between streamflow and desired instream flow adversely. Water storages were simulated on a daily basis to supply urban instream flow from Soho reservoir, but the amount of supplying instream flow to urban stream was not nearly increased comparing with that of normal operation that does not used the rule curve. Thereafter the new simulation-based operation rule curve was derived and applied to supply instream flow from Soho reservoir. In normal operation, the amount of instream flow was shown to 15,000 $m^3$/d, but it was increased to 27,700 $m^3$/d in withdrawal limited operation using the new derived rule curve, in which the applicability of this rule curve was proved. Also comparing with the flow duration curves at station just before urban Daejeoncheon stream without and with upstream Soho reservoir, the 95th flow was decreased from 1.64 mm/d to 1.51 mm/d, and the 355th flow was increased from 0.17 mm/d to 0.30 mm/d. Monthly streamflows during October to March were increased from 10.6~24.1 mm to 24.1~34.0 mm with the increasing rate of 141~227%.

• Advances in environmental research
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• v.3 no.1
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• pp.45-69
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• 2014

The groundwater has been a major source of water supply throughout the ages. Around 50% of the rural as well as urban population in the developing countries like India depends on groundwater for drinking. The groundwater is also an important source in the agriculture and industrial sector. In many parts of the world, groundwater resources are under increasing threat from growing demands, wasteful use and contamination. A good planning and management practices are needed to face this challenge. A key to the management of groundwater is the ability to model the movement of fluids and contaminants in the subsurface environment. It is obvious that the contaminant source activities cannot be completely eliminated and perhaps our water bodies will continue to serve as receptors of vast quantities of waste. In such a scenario, the goal of water quality protection efforts must necessarily be the control and management of these sources to ensure that released pollutants will be sufficiently attenuated within the region of interest and the quality of water at points of withdrawal is not impaired. In order to understand the behaviour of contaminant transport through different types of media, several researchers are carrying out experimental investigations through laboratory and field studies. Many of them are working on the analytical and numerical studies to simulate the movement of contaminants in soil and groundwater of the contaminant transport. With the advent of high power computers especially, a numerical modelling has gained popularity and is indeed of particular relevance in this regard. This paper provides the state of the art of contaminant transport and reviews the allied research works carried out through experimental investigation or using the analytical solution and numerical method. The review involves the investigation in respect of both, saturated and unsaturated, porous media.

• The KSFM Journal of Fluid Machinery
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• v.10 no.2 s.41
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• pp.41-45
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• 2007

The shutoff unit was designed to provide rapid insertion of neutron absorbing material into the reactor core to shutdown the reactor quickly and also to withdraw the absorber slowly to avoid a log-rate trip. Four shutoff units were installed on the HANARO reactor but the half-core test facility was equipped with one shutoff unit. The reactor trip or shutdown is accomplished by four shutoff units by insertion of the shutoff rods. The shutoff rod(SOR) is actuated by a directly linked hydraulic cylinder on the reactor chimney, which is pressurized by a hydraulic pump. The rod is released to drop by gravity, when triplicate solenoid valves are de-energized to vent the cylinder. The hydraulic pump, pipe and air supply system are provided to be similar with the HANARO reactor. The shutoff rod drops for 647mm stroke within 1.13 seconds to shut down the reactor and it is slowly inserted to the full down position, 700mm, with a damping. We have conducted the drop test of the shutoff rod in order to show the performance and the structural integrity of operating system of the shutoff unit. The present paper deals with the 647mm drop time and the withdrawal time according to variation of the pool water temperature, the water level and the core flow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.835-844
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• 2015

Streamflow responses to irrigation reservoirs and groundwater withdrawals were simulated using the integrated surface-water and groundwater model, SWAT-MODFLOW for the upstream watershed of the Gongdo station located in the Anseong stream. The simulated results indicated that the irrigation water supply from the Gosam and the Geumkwang reservoirs has caused the decrease of 31.2%, 82.5% in drought flows below the reservoirs, respectively, against the natural flow condition. While, at the outlet of the study watershed, the effects of the irrigation reservoirs were insignificant due to the delayed return flows with the decrease of 5.7% in drought flow. Both of the irrigation reservoirs and groundwater withdrawals have reduced the drought flows by 19.2% at the Gongdo station.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.231-243
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• 1994

A stochastic programming model for river water quality management was developed. River water quality, river flow, quality and flowrate of the wastewater treatment plant inflow were treated as random variables in the model. Withdrawal for water supply and submerged weir reaeration were included in the model itself. A probabilistic model was formulated to compute the expectation and variance of water quality using Streeter-Phelps equation. Chance constraints of the optimization problem were converted to deterministic equivalents by chance constrained method. Objective function was total annual treatment cost of all wastewater treatment plants in the region. Construction cost function and O & M cost function were derived in the form of nonlinear equations that are functions of treatment efficiency and capacity of treatment plant. The optimization problem was solved by nonlinear programming. This model was applied to the lower Han River. The results show that the reliability to meet the DO standards of the year 1996 is about 50% when the treatment level of four wastewater treatment plants in Seoul is secondary treatment, and BOD load from the tributary inflows is the same as present time. And when BOD load from Tanchon, Jungrangchon, and Anyangchon is decreased to 50%, the reliability to meet the DO standards of the year 1996 is above 60%. This results indicated that for the sake of the water quality conservation of the lower Han River, water quality of the tributaries must be improved, and at least secondary level of treatment is required in the wastewater treatment plants.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.375-380
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• 2013

The concept of safe yield places an emphasis on balancing groundwater withdrawal with groundwater recharge but ignores naturally occurring groundwater discharge. Because streams and their alluvial aquifers are closely linked in terms of water supply and water quality, to be properly understood and managed they must be considered together. Therefore, some districts in Kansas have reevaluated their safe-yield policies to account for natural groundwater discharge and stream-aquifer interactions by amending their safe-yield regulations to include a portion of baseflow as the minimum desirable streamflow (MDS). This study proposes a modified safe-yield policy in which the drought flow is chosen as the MDS. Baseflow separation was conducted from streamflow hydrograph and the results are presented as a flow-duration curve. The exploitable groundwater can be determined by subtracting MDS from the cumulative baseflow. This method was tested in the Musimcheon watershed, which was validated for streamflow using the SWAT-K model. The annually averaged exploitable groundwater in the whole watershed was estimated to be 86 mm. The exploitable groundwater amounts were also estimated for each subwatershed in the Musimcheon watershed.