• Journal of Life Science
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• v.18 no.12
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• pp.1671-1678
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• 2008

We investigated the effect of the turbid water on the phytoplankton community in the 4 sites of Imha reservoir. The turbidity of water was proportional to the concentrations of $SiO_2$-Si. Therefore, as the turbidity of water grow, the concentration of $SiO_2$-Si increased. And the both the turbidity of water and the concentrations of $SiO_2$-Si were increased as the water run deep. The concentration of chlorophyll-a decreased as the depth of water increased. Seventy phytoplankton taxa were identified and the most abundant group was Chlorophyceae consisting of 32 taxa (46%), and Cyanophyceae and Bacillariophyceae consisted of 12 taxa (17%). And Euglenophyceae, Synulophyceae, Cryptophyceae and Dinophyceae consisted of 6 taxa (9%), 4 taxa (6%), 3 taxa (4%) and 1 taxon (1%), respectively in Imha reservoir. The concentrations of phytoplankton were increased according to the turbidity of water because of the high amount of organic nutrition which is presented with turbid water. And especially, the concentrations of nitrogen increased easily because of the weak binding to the soil particle. In conclusion, total nitrogen and $SiO_2$-Si flowed into the Imha reservoir with soil particle, and these inorganic nutritions affect the growth of algae.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.228-235
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• 2007

For efficient turbid water withdrawal in the Imha reservoir, a selective withdrawal facility was recently installed and operated during summer season of year 2006. In this research, CE-QUAL-W2 model was utilized to assess the efficiency of the selective withdrawal facility, in comparison with the original surface withdrawal, on turbid water management. Model calibration was carried out using data observed at four automatic monitoring stations in the reservoir. It was found that the model appropriately simulated, with the RMSE less than 5.2 NTU, the observed vertical and horizontal distributions of water temperature and turbidity as well as the location of maximum turbid water at each monitoring station. The analysis results showed that selective withdrawal is more effective in removing high turbid water than surface withdrawal as selective withdrawal contributed to reducing $35Mm^3$ of high turbidity water (> 100 NTU) in the reservoir by increasing outflows of high turbid water. Therefore, effective management of turbid water in the reservoir can be achieved by changing locations of intake depending on turbid water distribution conditions. The results of this study will provide some basic information for establishing better operation strategies to cope with turbid water problems.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.4 s.31
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• pp.75-81
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• 2004

Because geological types and land cover conditions of Imha basin have a very weak characteristics to soil erosion, most soil particles (low into river and bring about high density turbidity in Imha reservoir when it rains a lot. This study used GIS-based RUSLE model and analyzed soil erosion to make basic data for the countermeasures of turbidity reduction in Imha reservoir. Total soil erosion amounts was evaluated as 5,782,829 ton/yr using rainfall data(2003) and especially Dongbu-basin was extracted as most source area or soil erosion among Imha sub-basin. Also it was evaluated that soil erosion amount by RUSLE model was suitable by applying turbidity survey data.

• Journal of Korean Society on Water Environment
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• v.30 no.1
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• pp.31-43
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• 2014

Recently, Andong Reservoir and Imha Reservoir located in Nakdong River basin (Korea) are being connected by a tunnel (length 2km, diameter 5.5m) for a conjunctive use. The objectives of this study were to construct a two dimensional(2D) laterally-averaged model for two reservoirs, and examine the effects of connection on the water transportation and temperature stratification in the reservoirs. The 2D models for each reservoir were calibrated using field data obtained in 2006, and applied to the linked system for the year of 2002 when a severe flood intruded into Imha Reservoir during the typhoon Rusa. Simulation results showed that 364 million $m^3$ of water can be conveyed from Imha to Andong, while 291 million $m^3$ of water from Andong to Imha after connection. It resulted in 1.38 m increase of annual averaged water level in Andong Reservoir, whereas 3.75 m decrease in Imha Reservoir. The structures of thermal stratification in both reservoirs were influenced in line with the flow exchanges. In Andong Reservoir, the location of thermocline moved upward about 10 m compared to an independent operation. The results imply that the persistent turbidity issue of Imha Reservoir might be shifted to Andong Reservoir during a severe flood event after connection.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.3
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• pp.99-107
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• 1995

Various humic substances are widely distributed in natural water body, such as rivers and lakes and cause the yellowish or brownish color to water. The evidence that humic substances are precursors of THMs formation in chlorinated drinking water has been reported m the Jiteratures. For the reason of public health as well as aesthetics, needs for humic substances removal have been increased in the conventional water treatment processes. In this research, the characteristics of aluminium coagulation of humic acids and humic acids were investigated. The optimum pH and coagulants dosage to remove these materials simultaneously by coagulation were alto studied. The results are as followed; 1. UV-254 absorptiometry for measuring the concentration of aquatic humic acids showed good applicability and stable results. 2. The optimal pH range for humic acids removal by aluminium coagulation was 5 to 5.5, however, an increase in aluminium coagulant dosage could enhance the removal rate of humic acids in the wide pH range. 3. Coprecipitation of humic acids in the typical pH range of 6.5 to 8 in water treatment processes may require the sweep coagulation mechanism with the excess aluminium coagulant dosage. 4. Using PAC(poly aluminium chloride) or PASS(poly aluminium silica sulfate) as coagulants was able to expand the operating range for removing humic acids. 5. From the coagulation of humic substances(UV-254) and turbidity at pH range of 5.5 - 6.0 and alum dose of 86 ppm, the removal efficiency of turbidity from the reservoir water was above 90% and that of UV-254 was above 70%. 6. By using the reservoir water, the optimum condition of rapid mixing for simultaneous removal of turbidity and UV-254 absorbance was pH of 5.8 and LAS dose of 86 ppm, in this study.

• Journal of Korea Water Resources Association
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• v.50 no.3
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• pp.201-210
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• 2017

This study proposes a numerical model which is able to simulate turbidity currents intruding into a reservoir and resulting sediment depositions. The proposed model is applied to laboratory experiments by Toniolo and Schultz (2005), and propagation of turbidity currents, morphological change, and trap of suspended sediment are simulated. It is simulated that the turbidity current after plunging at the foreset of the model delta, propagates along the bottom. The thickness of the turbidity current increases significantly after being blocked by the dam, and this effect is propagated in the upstream direction. In addition, it is simulated that the foreset moves in the downstream direction due to both the bedload and suspended load and the thickness of the bottom set increases due to the suspended load. It is found that the height of the intake affects the thickness of the turbidity current and the location of the internal hydraulic jump. The impact of the height of the intake on the trap efficiency is not clear in the experimental results, however, overall trap efficiency is predicted quite successfully by the model. Also, sensitivity analysis is carried out, and the results indicates that the particle size affects the trap efficiency most.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.423-430
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• 2004

This study intended to understand movements of turbid water in selective with drawal reservoirs before and after summer monsoon. Mean rainfall during November-May was low, compared to that during June-October. The reservoir water was discharged through watergates when previous rainfall and inflow exceeded 50 mm and $80\;m^3s^{-1}$, respectively. Intake towers were generally used except for the period of the high runoff. Average turbidity in gown-reservoir showed a difference of 29.9 NTU between premonsoon and postmonsoon. Diameter of particles of turbid water ranged between 0.435 and $482.9\;{\mu}m$. Fine particles such as clay were much denser than the larger particle. In the whole stations, clay component was relatively higher with a proportion of that in the particle distribution. Particle composition of turbid water showed that clay consisted of 94.4-98.9% and silt made of 1.1-5.6%. Analysis on turbid water movements derived from particle distribution showed a linear increase from the deep layer toward the surface layer in lower area of a reservoir. This was closely related with the hydraulic behavior of the reservoir, and heavily affected by the discharges through selective withdrawal towers and watergates. Turbid water originated from stream sediments in the middle area then resuspended in the down-reservoir causing a movement between the surface and middle layers of the reservoir. Therefore, such phenomenon needs to be understood for reservoir water quality management.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1209-1210
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• 2005

• Journal of Environmental Science International
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• v.23 no.5
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• pp.839-852
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• 2014

The Ministry of Environment (MOE) has made more effort in managing point source pollution rather than in nonpoint source pollution in order to improve water quality of the four major rivers. However, it would be difficult to meet water quality targets solely by managing the point source pollution. As a result of the comprehensive measures established in 2004 under the leadership of the Prime Minister's Office, a variety of policies such as the designation of control areas to manage nonpoint source pollution are now in place. Various action plans to manage nonpoint source pollution have been implemented in the Soyang-dam watershed as one of the control areas designed in 2007. However, there are no tools to comprehensively assess the effectiveness of the action plans. Therefore, this study would assess the action plans (especially, BMPs) designed to manage Soyang-dam watershed with the WinHSPF and the CE-QUAL-W2. To this end, we simulated the rainfall-runoff and the water quality (SS) of the watershed and the reservoir after conducting model calibration and the model validation. As the results of the calibration for the WinHSPF, the determination coefficient ($R^2$) for the flow (Q, $m^3/s$) was 0.87 and the $R^2$ for the SS was 0.78. As the results of the validation, the former was 0.78 and the latter was 0.67. The results seem to be acceptable. Similarly, the calibration results of the CE-QUAL-W2 showed that the RMSE for the water level was 1.08 and the RMSE for the SS was 1.11. The validation results(RMSE) of the water level was 1.86 and the SS was 1.86. Based on the daily simulation results, the water quality target (turbidity 50 NTU) was not exceeded for 2009~2011, as results of maximum turbidity in '09, '10, and '11 were 3.1, 2.5, 5.6 NTU, respectively. The maximum turbidity in the years with the maximum, the minimum, and the average of yearly precipitation (1982~2011) were 15.5, 7.8, and 9.0, respectively, and therefore the water quality target was satisfied. It was discharged high turbidity at Inbuk, Gaa, Naerin, Gwidun, Woogak, Jeongja watershed resulting of the maximum turbidity by sub-basins in 3years(2009~2011). The results indicated that the water quality target for the nonpoint source pollution management should be changed and management area should be adjusted and reduced.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.31-39
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• 2007

In this study we developed a turbidity management system to support the operation for effective turbid water management. The decision-making system includes various models for prediction of turbid water inflow, effective reservoir operation using the selective withdrawal facility, analysis of turbid water discharge in the downstream. The system is supported by the intensive monitoring devices installed in the upstream rivers, reservoirs, and downstream rivers. SWAT and HSPF models were constructed to predict turbid water flows in the Imha and Andong catchments. CE-QUAL-W2 models were constructed for turbid water behavior prediction, and various analyses were conducted to examine the effects of the selective withdrawal operation for efficient high turbid water discharge, turbid water distribution under differing amount and locations of turbid water discharge. A 1-dimensional dynamic water quality model was built using Ko-Riv1 for simulation of turbidity propagation in the downstream of the reservoirs, and 2-dimensional models were developed to investigate the mixing phenomena of two waters discharged from the Andong and Imha reservoirs with different temperature and turbidity conditions during joint dam operation for reducing the impacts of turbid water.