• The Journal of Engineering Geology
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• v.19 no.2
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• pp.131-138
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• 2009

A simulation-optimization model is developed for development of groundwater and control of a saltwater wedge for protecting over-exploiting freshwater pumping wells. To achieve the goal an objective function is developed for three types of wells: freshwater pumping, freshwater injection and saltwater pumping. Integrity of groundwater environment is accounted for by including three indices. Illustrative cross-sectional examples show that both types of barriers can protect freshwater pumping wells from saltwater intrusion. A barrier well operating at the same rate located anywhere within a certain reach can protect a pumping well. However, the location of the reach appears to contradict the common practice of barrier placements. Consideration of the groundwater environment yields a unique optimal location for barrier wells.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.89-96
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• 2020

Water management agencies under the Ministry of Environment produce and accumulate qualified basic data for major rivers. However, the integrated management of the river water has been weak since the artificial water circulation process, such as the intaking and drainage of agricultural water, has not been examined in the basin, which includes many agricultural land. In this study, a study was conducted on how the power usage method (operating time method) based on the running time can be applied and improved among indirect flow rate measurement methods used to investigate flow rates collected by the riverside for agricultural water purposes, and thus the resultant data of high reliability can be obtained at low cost. The operation time method is suitable for small-scale water pumping stations where it is difficult to secure real-time power supply data. The reliability of the data was verified through the correlation analysis with the actual flow rate, and it was found that the flow rate calculated by the operation time method reflecting the level of the stream to which the inlet of the pumping station is connected can be reasonably matched with the actual flow rate. In addition, it was confirmed that the investment cost at the time of initial installation of the facility was highly efficient by generating qualified flow data at low cost through comparison with direct flow rate measurement methods. If flow data is secured by applying the operation time method to large and small water farms located along the riverside, it is expected that more quantitative and integrated stream water management will be possible.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.6
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• pp.57-69
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• 1998

The creation of favorable water space, in our living circumferential space, is very important factor to offer rural scenery to neighbor residents. We are to introduce stream landscape arrangement technique considering favorable water environment against conventional methods. In this study, the modeling district is Seungdu small stream of Ansung river system in Pyung-Teak city, Kyonggi province, and we carried out stream landscape simulation. The arranging plans of landscape are classified ti three types. The first one is conservation type of ecological environment that can express natural characteristics of stream inherence, raise variety of living things and construct coexisting environment between human beings and the other living things. The secong one is favorable water approach type. The basic object of this type is space construction for easy approach to waterside and increase of comfortable feelings of spectators. The third one is water utilization/flood control management type. In planning of environmentally favorable landscape arrangement, this type is the most important but is likely to be ignored. This type is an arranging plan of stream landscape considering safety. Also, we developed Streams Landscape Simulation System(SLSS). This program can be used for comparison of original landscape image with simulated one. To apply SLSS on the interested stream, landscape simulation that is based on hydraulic characteristics, runoff, flow direction, detailed conditions of basin and ecosystem of stream have to be executed. In this point, developing a stereographical technique of image processing and exact study of applying plan have to be executed continually.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1243-1258
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• 2012

The objective of this study is to develop the relational formula to estimate the streamflow depletion due to groundwater pumping near stream, which has been statistically derived by using the simulated data. The integrated surface water and groundwater model, SWAT-MODFLOW was applied to the Sinduncheon and Juksancheon watersheds to obtain the streamflow depletion data under various pumping conditions. Through the multiple regression analyses for the simulated streamflow depletion data, the relational formula between the streamflow depletion rate and various factors such as pumping rate, distance between well and stream, hydraulic properties in/near stream, amount of rainfall was obtained. The derived relational formula is easy to apply for assessing the effects of groundwater pumping on near stream, and is expected to be a tool for estimate the streamflow contribution to the pumped water.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.311-320
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• 2021

The agricultural water, which occupy about 61% of total water usage in the South Korea, is significantly objective to archieve effecitive water resources management. The objective of the study is to suggest a simple method in actual practice that could be used to estimate agricultural water usage in river considering hydrological condition. Historical record of agricultural water usage and runoff, which take account for hydrological condition of the basin, were obtained for totally 27 river basins. As the result, the high threshold value of the agricultural water usage rates compared to maximum usage amount has a particular correlations to the percent of normal year runoff for last 2 month, and threshold line of agricultural water usage rates was derived using the quantile regressions. Finally, two dimensionless threshold line and empirical formulas that described the correlation between the percent of normal year runoff for last 2 month and the agricultural water usage rate compared to maximum usage amount were derived. Also, the simple criteria to select which line and formula based on the characteristics of the basins was suggested but it need further studies. The result of the study could be used as an elemantary data in actual practice for water resoureces management.

• Journal of Korean Society on Water Environment
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• v.32 no.5
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• pp.433-441
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• 2016

Many large dams have been constructed for water supply, irrigation, flood control and hydropower in Korea for the last century. Meanwhile, recent studies indicated that the artificial reservoirs impounded by these dams are major sources of carbon dioxide (CO₂) to the atmosphere and relevant to global budget of green house gases. However, limited information is available on the seasonal variations of CO₂ evasion from the reservoirs located in the temperate monsoon regions including Korea. The objectives of this study were to estimate daily Net Atmospheric Flux (NAF) of CO₂ in Daecheong Reservoir located in Geum River basin of Korea, and analyze the influencing parameters that characterize the variation of NAF. Daily pH and alkalinity (Alk) data collected in wet year (2012) and dry year (2013) were used for estimating the NAFs in the reservoir. The dissolved inorganic carbon (DIC) was computed using the pH and Alk measurements supposing an equilibrium state among the carbonate species. The results showed seasonal variations of NAF; negative NAFs from May to October when the primary production of the reservoir increased with water temperature increase, while positive NAF for the rest of the period. Overall the reservoir acted as sources of CO₂ to the atmosphere. The estimated NAFs were 2,590 and 771 mg CO₂ m^-2d^-1 in 2012 and 2013, respectively, indicating that the NAFs vary a large extent for different hydrological years. Statistical analysis indicated that the NAFs are negatively correlated to pH, water temperature, and Chl-a concentration of the reservoir.

• Journal of Korea Water Resources Association
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• v.45 no.10
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• pp.1051-1067
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• 2012

Increased use of water curtain facilities to keep green house warm during winter cultivation has been known to cause excessive groundwater ion which might lead to decline of groundwater level, resulting in streamflow depletion. Therefore it is required to quantitatively assess the effects of groundwater ion on the streamflow depletion such as magnitude and extent. The objective of this study is to assess the change of stream-aquifer interaction according to groundwater ion near stream. To this end, a green house cultivation land in Sooha-ri, Sindun-myun, Icheon-si, Gyonggi-do was selected as a field experimental site, and monitoring wells were established near and within stream to observe the water level and temperature changes over a long period of time. From the observed water level and temperature data, it was found that the river reach of interest changed to a losing stream pattern during the winter cultivation season due to groundwater level decline around pumping wells near the stream. The continuous exchange rates between stream and aquifer were estimated by plugging the observed water level data series into the experimental relation between head difference and exchange rate, showing the streamflow depletion by 16% of the groundwater pumping rate in Feb, 2011.

• Journal of Korea Water Resources Association
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• v.49 no.2
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• pp.95-106
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• 2016

Water Management Resilience Index (WMRI) was developed as a policy measure of adaptability to withstand water stresses and to set up water management strategies mainly in mid-small scale tributaries, and then evaluated on 117 sub-basins in South Korea. The index consists of 3 sub-indices such as vulnerability, robustness and redundancy sub-indices, each including indicators of 3 sectors: water use, flood mitigation, and river environment. Total number of indicators selected for the index was 31. Taking into account the stream order and control capability of river flow discharge, sub-basins were categorized into 3: 1 for mainstreams of lower large dams, 2 and 3 for tributaries, respectively without and with flow discharge regulation. As a result of the evaluation, resilience index scores in Category 2 and 3 are much lower than that of Category 1, especially with very poor score of redundancy. Although there was no significant difference between mainstream and tributaries in vulnerability and robustness sub-indices, results of redundancy sub-index in tributaries were lower than those in mainstream. Thus, it is conceived that the variety of water management schemes should be considered to improve their resilience in the face of future uncertainty. Addressing comprehensive stability of river basin against internal and external impacts, WMRI in this study can also be used for the prioritization of water management plans.

• Journal of Korea Water Resources Association
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• v.48 no.6
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• pp.501-509
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• 2015

Lately multipurpose dam is required to consider various interests such as quality, ecological environment as well as flood control, water supply, hydropower generation, etc. The objective of this study is to investigation and analysis of water temperature in the areas where there are social conflicts due to cold water outflow. In this study, we monitored water temperature of Juam regulation dam, downstream river, Suncheon bay in a long term period and performed comparative analysis on a change of water temperature in downstream river and Suncheon bay by using three-dimensional numerical mode (EFDC) considering various external factors such as water outflow amount. The result of monitoring and numerical modelling indicates that effects of cold water outflow takes place from april to september. Also effects of the low temperature discharge of dam was complicatedly altered by various factors such as outflow time and amount, weather and tide level conditions etc. The result of this study can be utilized as a basic data for establishing improvement of dam operation plan to minimize negative effects of dam's cold temperature water outflow to downstream river and coastal area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5B
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• pp.497-507
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• 2010

Climate changes affect greatly natural ecosystem, human social and economic system acting on constituting the climate system such as air, ocean, life, glacier and land, etc. and estimating the current impact of climate change would be the most important thing to adapt to the climate changes. This study set the target area to Nakdong river watershed and investigated the impact of climate changes through analyzing precipitation tendency, and to understand the impact of climate changes on hydrological elements, analyzed elasticity of precipitation-streamflow. For the analysis of precipitation trend, collecting the precipitation data of the National Weather Service from major points of Nakdong river watershed, resampling them at the units of year, season and month, used as the data of precipitation trend analysis. To analyze precipitation-streamflow elasticity, collecting area average precipitation and long-term streamflow data provided by WAMIS, annual and seasonal time-series were analyzed. In addition, The results of this study and elasticity, and other abroad study compared with the elasticity analysis and the validity of this study was verified. Results of this study will be able to be utilized for study on a plan to increase of flood control ability of flooding constructs caused by the increase of streamflow around Nakdong river watershed due to climate changes and on a plan of adapting to water environment according to climate changes.