• Proceedings of the Korea Water Resources Association Conference
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• 1998.05a
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• pp.197-202
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• 1998

• IE interfaces
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• v.23 no.4
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• pp.311-318
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• 2010

In the daily multi-reservoir operating problem, monthly storage targets can be used as principal operational guidelines. In this study, we tested the use of a simple back-propagation Artificial Neural Network (ANN) model to derive monthly storage guideline for daily Coordinated Multi-reservoir Operating Model (CoMOM) of the Han-River basin. This approach is based on the belief that the optimum solution of the daily CoMOM has a good performance, and the ANN model trained with the results of daily CoMOM would produce effective monthly operating guidelines. The optimum results of daily CoMOM is used as the training set for the back-propagation ANN model, which is designed to derive monthly reservoir storage targets in the basin. For the input patterns of the ANN model, we adopted the ratios of initial storage of each dam to the storage of Paldang dam, ratios of monthly expected inflow of each dam to the total inflow of the whole basin, ratios of monthly demand at each dam to the total demand of the whole basin, ratio of total storage of the whole basin to the active storage of Paldang dam, and the ratio of total inflow of the whole basin to the active storage of the whole basin. And the output pattern of ANN model is the optimal final storages that are generated by the daily CoMOM. Then, we analyzed the performance of the ANN model by using a real-time simulation procedure for the multi-reservoir system of the Han-river basin, assuming that historical inflows from October 1st, 2004 to June 30th, 2007 (except July, August, September) were occurred. The simulation results showed that by utilizing the monthly storage target provided by the ANN model, we could reduce the spillages, increase hydropower generation, and secure more water at the end of the planning horizon compared to the historical records.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.4
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• pp.73-86
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• 1995

The propriety of the numerical model application was examined on Paldang resevoir and its inflow tributaries located in the center of the Korean peninsula and the long term water quality forecast of the oxygen profile was carried out in this syduy. The input data of the model was the capacity of the reservoir, catchment area, percolation, diffusion rate, vertical mixing rate, dissolution rate from the bottom of the reservoir, outflow of the resevoir, water quality measurement and meteorology data of the drainage basin, and the output result was the annual estimation value of the dissolved oxygen concentration and the biochemical oxygen demand. The modeling method is based on the measured or calculated boundary condition dividing the water area into several blocks from the macorscopic aspect and considering the mass balance in these blocks. As the result of the water quality forecast, it was expected that the water quality in Northern Han River and Paldang reservoir would maintain the recent level, but that the water quality in the Southern Han River and its inflow tributary would worsen below the grade 4 of the life environmental standard from around 2000 owing to the decrease of DO concentration and the increase of BOD concentration.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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• pp.277-283
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• 2005

This paper aimed to compare the daily water quality as well as the hydrological data gathered for the past two years (2000 to 2001) between the two influent rivers of Paldang reservoir. The analysis also has been carried out to draw out the factors that affect the water quality at the dam site, where the main drinking water drawing point is located. The relationship between total amount of monthly rainfall and monthly inflow showed $r^2=0.74$ (p<0.05). The highest peak of inflow of influent rivers recorded in August and September (in the year of 2000) and July and August (2001). Average inflows of influent rivers in 2000 and 2001 are calculated at 209.0, 161.5 CMS (Bughangang), 268.6, 148.2 CMS(Namhangang), and 7.8, 5.0 CMS (Gyeongancheon). The formula which was driven from the relationship between inflow and COD load of influent rivers, explained that COD concentration in general increased with the inflow. But during the rainy seasons (July, August, and September), COD concentration decreased according to the increase of inflow. The daily rainfall and COD concentration(or load) during the rainy season (August and September in the year of 2000, July and August in 2001) indicated that the peak of COD load correspond with the rainfall, which decreased sharply after 3 or 4 days. The reason was thought that the high COD load was diluted rapidly by the rain flow. Water temperature, pH and conductivity measured at dam site decreased obviously when the inflow sharply increased. Peak period of total phosphorus concentration coincided with that of inflow. In rainy season, chlorophyll-a concentration decreased obviously as the inflow increased. The reason can be ascribed to the flushing effect caused by the operation of floodgate.

• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.10-20
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• 2002

Changes of seasonal and vertical water quality was analyzed with physico-chemical data from Soyang and Paldang river-reservoir system in Korea during the 1996 to 1998. In Soyang river-reservoir system, the water column was well stratified, which narrow epilimnion layer of 5 to 10 m depth in spring to summer enlarged gradually about 40 m depth in fall as going to times. In contrast, metalimnion layer tended to be narrow during the same period. Water temperature of hypolimnion was maintained about $5^{\circ}C$ continuously throughout the year. DO of the epilimnion layer was supersaturated from spring to summer, however, it was decreased to 75% at the epilimnion layer and $45{\sim}50%$ at the hypolimnion layer at the late fall. The lowest conductivity of below $50\;{\mu}S/cm$ was observed at the metalimnion layer during thesummer to fall. In Paldang river-reservoir system, the water column wag well mixed layer throughout the year, although water temperature was changed seasonally from $5^{\circ}C$ in February to $28^{\circ}C$ in July. Water temperature between upper and lower layer was different about $5^{\circ}C$ from late spring (May) to early fall (September). DO was over and less saturated in upper and lower layer during the early summer to early fall, respectively. Conductivity was decreased to $90\;{\mu}S/cm$ in lower layer of below $4{\sim}5\;m$ depth during the late spring to early fall and that of upper layer of above 10 m depth decreased to about $100\;{\mu}S/cm$ during the late fall (November) and early spring (March). Retention time of Soyang river-reservoir system was much longer than that of Paldang river-reservoir system. Chlorophyll a, T-N and T-P concentration in Paldang river-reservoir system were higher than that of Soyang river-reservoir system by a factor of 2.7, 1.2 and 2.6, respectively. Algal blooming was deeply affected by the nutrients than the retention time.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.424-434
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• 2006

This study investigates bacteria-zooplankton grazing link and factors affecting their grazing relationship at trophically different two sites (Paldang Dam and Kyungan Stream) of Lake Paldang Ecosystem from April to December, 2005. Zooplankton were divided into two size groups; microzooplankton (MICZ) : 60-200 ${\mu}m$ and macrozooplankton (MACZ): >200 ${\mu}m$), and their grazing rates on bacteria were conducted for each size group separately. Bacterial abundance and seasonal change pattern were similar between two sites. MICZ, mostly rotifers (e.g., Brachionus, Keratella, Polyathra) were numerically dominant at both sites, while carbon biomass was highest in cladocerans. Zooplankton biomass was higher at the Kyungan Steam site compared to Paldang Dam site, and their high biomass during spring decreased as they were passing through the storm events in summer season at both sites. Zooplankton clearance rate (CR) was high in spring and autumn while low in summer at Paldang Dam site. However, zooplankton CR was high during the summer at Kyungan Stream site. Bacterial C-flux was high in spring and autumn when MACZ (esp. cladecerans) developed at a high biomass level at both sites. Overall, MACZ community CR and carbon flux (C-flux) were higher than those of MICZ, and the degree of difference between them was higher at Kyungan Stream site. Short hydraulic residence time and physical disturbance caused by summer storm event appeared to affect the zooplankton grazing on bacteria at both sites. The results of this study indicate that bacteria are potentially important carbon source of zooplankton, and that both biotic (e.g,, prey and predator taxa composition and abundance) and physical parameters appear to alter energy transfer in the planktonic food web of this river-reservoir hybrid system.

• Korean Journal of Environmental Biology
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• v.20 no.1
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• pp.91-99
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• 2002

With physico-chemical environmental factors such as temperature, DO, pH, conductivity and nutrients, size fractionated of phytoplankton standing crops and chlorophyll a concentrations $(>8\mu{m},\;3-8\mu{m},\;<3\mu{m})$ and their relationships were investigated at each station of Kyungan Stream and Togyo Reservoir from April to November in 1997. The two sampling sites showed different nutrient status: Kyungan Stream was eutrophic, while Togyo Reservoir was mesotrophic. Large sizes of phytoplankton and chl. a were higher in Kyungan Stream, opposite to those of Togyo Reservoir; Standing crops of phytoplankton $(>8\mu{m)$ and chl. a $(3-8\mu{m)}$ were high in Kyung-an Stream, while phytoplankton $(3-8\mu{m)}$and chi. a $(<3\mu{m)$ were abundant in Togyo Reservoir. These results imply that phytoplankton community in the highly eutrophicated water mainly comprised the large filamentous and/or colonial algae, such as Microcystis spp. and Aphanizomenon flos-aquae, which easily enriched by nutrients loading.

• Animal cells and systems
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• v.7 no.4
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• pp.289-294
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• 2003

To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.

• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.354-374
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• 2016

This study explored spatiotemporal variability of water quality in correspondence with hydrometeorological factors in the five stations of Paldang Reservoir located in the Han River during 4 years from May 2012 to December 2015. Variability of basic water quality factors were largely related with seasonal fluctuations of hydrology. Temperature stratification occurred in the deep dam station, and prolonged hypoxia was observed during the draught year. Nitrogen nutrients were increased with decreasing inflow in which changing pattern of $NH_4$ reversed to $NO_3$ by the effect of treated wastewater effluent. Phosphorus increase was manifest during the period of high inflow or severe drought. Chl-a variation was reversely related with both flow change and AGP(algal growth potential) variations. Our study demonstrated that water quality variability in Paldang Reservoir was largely attributed to both natural and operational changes of inflow and outflow (including water intake) based on major pollution source of the treated wastewater (total amount of $472{\times}10^3m^3d^{-1}$) entering to the water system from watershed. In the process of water quality variability, meteorological (e.g., flood, typhoon, abnormal rainfall, scorching heat of summer) and hydrological factors (inflow and discharge) were likely to work dynamically with nutrients pulse, dilution, absorption, concentration and sedimentation. We underline comprehensive limnological study related to hydro-meteorolology to understand short- and long-term water quality variability in river-type large reservoir and suggest the necessity of P-free wastewater treatment for the effective measure of reducing pollution level of Paldang drinking water resource.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.5
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• pp.367-377
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• 2014

Paldang lake which is the most important water resource in Korea is classified as a stream type reservoir and water quality of Paldang lake can be significantly influenced by external pollutant source. So this study was aimed to determine focused control BOD and TP sources of each unit watershed upper Paldang lake through analysis of pollutant source distribution and pollutant runoff characteristics. Generated load, discharge load, delivery load and each load density of 11 unit watersheds upper Paldang lake were calculated using data of water quality and flow rate from pollutant sources and 74 small streams. As a result of generated load, discharge load and delivery load of BOD and TP from pollutant sources, the most BOD generated load was taken by livestock with 66% of total BOD discharge load and domestic had the most BOD discharge load, 42.7%. The ratio of delivery load of livestock and domestic was 36.4% and 34.3%, respectively. Livestock occupied high ratio of TP generated load, discharge load and delivery load with 82.5%, 44.4% and 46.7%, respectively. Gyeongan watershed which had high population density showed the highest BOD delivery load density of $14.6kg/km^2/d$ and the highest TP delivery load density with $1.23kg/km^2/d$ was analyzed in Cheongmi watershed including the biggest number of livestock. From these results, management of domestic sewer and livestock excrement was determined as a focused control pollutant source. And intensive management about domestic sewer in Gyeongan stream and livestock excrement in Cheongmi stream is required for water quality improvement of Paldang lake.