• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.187-192
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• 1997

We carried out a survey on tributary streams in some agricultural areas along Nakdong River to evaluate the effects of agricultural practices on pollution of stream water and groundwater. General properties, nutrient materials and heavy metals in water samples were measured. General physicochemical properties of tributary stream waters were at levels favorable for agricultural water. Heavy metals, except Zn, were mostly not detected. Total-N contents were much higher than the criteria of agricultural water, and nitrate-N accounts for more than a half of total-N. Phosphorus contents were higher than the lower level of P for algae growth and the contents were high especially in summer. In ground waters which are used for irrigation, P were mostly at same levels as those in streams, and nitrate contents were higher than 10mg/L in some samples. In these results only those N and P contents in stream and ground waters higher than pollution criteria are problematic and they are traceable to agricultural nonpoint sources-fertilizers, livestock farms and sewage. Further researches are needed to evaluate contributions of each nonpoint source on stream water pollutions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.83-92
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• 2019

A pump is considered to be submersible when a motor and a pump are integrated and operate while submerged in water. Submersible pumps mainly function as rejection pumps to prevent foods in densely populated areas, as cold water circulation pumps in large power plants, as pumps to supply irrigation water, as drainage pumps to prevent flooding of agricultural lands, as water supply intake pumps, and as inflow pumps for sewage treatment. The flow in such turbomachines (submersible pumps) inevitably involves various eddy currents. Since it is almost impossible to accurately grasp the complex three-dimensional flow structure and characteristics of a rotating turbomachine through actual testing, three-dimensional numerical analysis using computational fluid dynamics techniques measuring the flow field, velocity, and the pressure can be accurately predicted. In this study, the shape of the impeller was developed to reduce vibration and noise. This was done by increasing the efficiency of the existing submersible pump and reducing turbulence. In order to evaluate the pump's efficiency and turbulence reduction, we tried to analyze the flow using ANSYS Fluent V15.0, a commercial finite element analysis program. The results show that the efficiency of the pump was improved by 4.24% and the Reynolds number was reduced by 15.6%. The performance of a developed pump with reduced turbulence, vibration, and noise was confirmed.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.223-231
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• 1999

This study was carried out to investigate the factors influencing water quality of the river (Mankyeong River) and groundwater in controlled horticulture region from 1994 to 1998. Water quality of Mankyeong River was monitored at 13 sites along main stream for 6 months from April to September from 1994 to 1997. Monthly average concentrations of $NH_4-N$, $SO{_4}^{2-}$ and $Cl^-$ were highest in April, while that of $NO_3-N$ was highest in August. Monthly average concentrations of COD was highest in September Concentrations of $NH_4-N$ and $SO{_4}^{2-}$ in many sites of Mankyeong River exceeded the water quality criteria of agricultural water for irrigation. Water quality of Mankyeong River was not suitable for the irrigation source excepted the sites such as Hari, Gosan and Soyang stream. The floodgates of Mokcheon, Yocheon, Jeonju and Samcheon streams were rapidly polluted by the municipal sewage, otherwise the Iksan stream was rapidly polluted by the sewage of swine. The sum of inorganic ion concentrations in Mankyeong River was highest at floodgate of Yocheon due to the sewages municipal and industrial. The order of the major anions and canons concentration in Mankyeong River- stream were $SO{_4}^{2-}$ > $Cl^-$ > $NO{_3}^-$ > $PO{_4}^{3-}$ and $Na^+$ > $Ca^{2+}$ > $NH{_4}^+$ > $Mg^{2+}$ > $K^+$, respectively. The geoundwater quality at controlled horticulture region was surveyed 4 sites from 1994 to 1998. Concentrations of $NH_4-N$ and $NO_3-N$ were lower at the deeper groundwater. However there was no difference between the concentrations of $SO{_4}^{2-}$ and $Na^+$, and the groundwater depth below 15m. Contents of $NH_4-N$, $NO_3-N$, $PO{_4}^{3-}$, $SO{_4}^{2-}$, $Na^+$ and $Cl^-$ in groundwater were the highest at dry season. Nitrate-N level, exceeded $20mg\;l^{-1}$, the critical level for agricultural usage, at Yongjinmyeon Wanju and $PO{_4}^{3-}$ concentration were higher at Seogtandong Iksan than the other places.

• Current Research on Agriculture and Life Sciences
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• v.1
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• pp.85-93
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• 1983

Total annual water requirements for agricultural use are exceedingly large. In many areas of the country, particularly in the arid regions, irrigation water requirements comprise the bulk of the total developed water supply. On the other hand, we are, at present, poorly prepared to evaluate the hazards of many substances in the water phase of the agricultural environments. This study is to survey the water quality phase of agricultural conditions and to give some ideas to prevent disasters from the environmental hazards such as PH, Electric Conductivity, BOD, DO, Cu, Pb, and Cd. In the analysed results, mean PH was 6.5 to 7.8, maximum EC was $200{\mu}{\Omega}/cm$ at $25^{\circ}C$, the maximum BOD was less than 10 ppm (standard value), the DO was 4.2 to 12.0 mg/L (standard value is more than 2.0 mg/L) and the Cu, Pb, Cd were estimated in scope of safety value respectively. Especially BOD is gradually closed with the hazardous point in the few places. At present, the hazardous environmental conditions originated from the municipal sewage, industrial waste, and human and domestic animals excrements etc. have to strongly be improved much better than before.

• Journal of the Korean Regional Science Association
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• v.34 no.1
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• pp.19-30
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• 2018

Social overhead capital(SOC) is an essential element for society to be developed and operated normally. In spite of the increase in the importance of SOC, It is difficult to present the criteria for the appropriate investment of SOC. and The discussion on making SOC investments of local government is insufficient. If the local autonomy has been guaranteed, local government increases investment in regional public goods that residents prefer. Reflection of such residents preferences is the driving force to bring the efficiency of resource allocation in the decentralization theorem. In this study, the authority and autonomy of local governments are measured through local finance. and the decision-making of local governments for SOC investment is examined in point of decentralization theorem. In the empirical analysis, the elasticities of fiscal resources are estimated for facilities(road, water and sewage, irrigation canal and flood control) that local governments are involved in investment. These decisions made by metropolitan cities and provinces were different. The difference was most evident in the effect of per capita local tax on investment. These results show that metropolitan cities and provinces that have different situation made investment decisions differently. It shows that local governments reflect the preferences of the residents in making an investment. The main implication of this study is as follow. In case the role of local government in social overhead capital investment is increased, the increase in efficiency of resource allocation occurs. and The fiscal resources must be raised by local taxes rather than the financial resources from the central government.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.421-429
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• 2012

This study was aimed to analyze the water quality characteristics of the Hwapocheon Stream and to be utilized in the further related research. Water in the upper stream became a dammed pool due to the existence of 14 weirs, and pollutants such as both sewage and irrigation water were introduced into the mainstream passing through farming settlements and agricultural land. For these reasons, filamentous cyanobacteria (Oscillatoria sp.) bloomed at the bottom of the dammed pool. Also in the midstream and downstream, tributaries with high pollutant concentrations [e.g., Comocheon (T3) and Yongdeokcheon (T8)] were inflowed, and had a negative impact on water quality of the mainstream, especially nitrogen and phosphorus. In the Hwapocheon Stream, dissolved oxygen (DO) decreased, and suspended solid (SS) increased toward the downstream. The result showed that hydraulic retention time, SS, COD, and concentration of $NH_4{^+}$ were important water quality factors of the Hwapocheon Stream. The high concentration of benthic organic matter and rich in attached algae in the core of Hwapo-wetland were expected to give impact on the water quality of the mainstream. In the spatial manner, water quality showed increasing trend in the weir zone, and it was constant or decreased trend in wetland. In the seasonal manner, the nutrient concentrations were high in the winter dry season, however, the organic matter concentrations were high in spring and summer. Generally, the concentrations of phytoplankton value were $40{\mu}g\;chl-{\alpha}/L$ or less in all reaches except for the high concentrations in the weir and wetland area in June.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1259-1273
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• 2012

In this study, a watershed-based surface water and groundwater integrated model, SWAT-MODFLOW was used to quantify the stream flow depletion due to groundwater pumping for the Sinduncheon watershed. Complex water use conditions such as water taken from a stream, sewage disposal release, irrigation from agricultural reservoir, groundwater pumping were considered for simulations. In particular, the model was revised to reflect the effects of reservoir operation and return flow from the used groundwater on streamflow variation. The simulated results showed that the groundwater pumping at current status has induced the decrease of more than 10% in annual average streamflow and 40% in drought flow at the outlet of the Sinduncheon watershed, The simulated results also revealed that the vast water withdrawals at green house areas during winter season have dramatically changed streamflow from April to June. The streamflow depletion was mainly attributed to pumping wells located within the distance of 300 m from the stream for Sinduncheon watershed.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.4
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• pp.237-244
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• 2006

The SMG project has been driven to secure food and water resources by closing of the SMG dyke for the preparation of the unification of Korean peninsular. It was investigated for pollution loads, land use distribution and water consumption for environmental assessments in two watersheds, the Mankyeong River (MK) and the Dongjin River (DJ) to assess the role of agricultural land on the alleviation of pollution loads to the SMG basin. It is needed to give the priority in managing pollution sources to conserve freshwater in the Saemangeum (SMG) basin after the completion of the SMG reclamation from tideland. The MK has $700million\;m^3$ water of which 14.1% were used for living, 73.6% for agriculture and 12.3% for industry. The DJ has $505million\;m^3$ water of which 3.0% for living, 94.5% for agriculture and 2.5% for industry. As compared to proportion of each land of total area, agricultural land was 1.4 times larger, livestock farming 7 times larger, forest 0.74 times smaller, and built-up area 0.67 times smaller in DJ watershed than in MK watershed. Pollution sources in MK and DJ watersheds were originated at a higher proportion from population including the sewage disposal and a livestock farming area rather than from the land. Water consumption and land use distribution influenced the water quality of the rivers; DJ watershed had far lower value of electric conductivity, $BOD_5$, TN and TP than MK watershed. A large proportion of paddy field also influenced to reduce pollute loadings after rainfall; DJ watershed, which has a relatively large area of paddy fields, had a far lower delivery load after rainfall than MK watershed even though DJ watershed had large livestock farming area. As paddy fields was irrigated by Iksancheon water, 37% of nitrogen, 50% of phosphates and 14.0% of $BOD_5$ was removed by the paddy field just after flowing 150 meter, and rice plants could remove TN 100.0 kg, $P_2O_5$ 24.0 kg, and $K_2O$ 119.2 kg per hectare at harvest by irrigation of Iksancheon water. Conclusively, rice paddy fields played a positive role to conserve the water quality in the Iksancheon watershed.

• The Korean Journal of Quaternary Research
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• v.14 no.1
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• pp.7-31
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• 2000

Quaternary Geological and geophysical investigation was performed at the Eurimji reservoir of Jaechon City in order to interprete depositional environment and genesis of lake sediments. For this purpose, echo sounding, bottom sampling and columnar sampling by drilling on board and GPR survey were employed for a proper field investigation. Laboratory tests cover grain size population analysis, pollen analysis and $^{14}C$ datings for the lake sediments. The some parts of lake bottom sediments anthropogenically tubated and filled several times to date, indicating several mounds on the bottom surface which is difficult to explain by bottom current. Majority of natural sediments were accumulated both as rolling and suspended loads during seasonal flooding regime, when flash flow and current flow are relatively strong not only at bridge area of the western part of Eurimji, connected to stream valley, but at the several conduit or sewage system surrounding the lake. Most of uniform suspend sediments are accumulated at the lake center and lower bank area. Some parts of bottom sediments indicate the existence of turbid flow and mudflow probably due to piezometric overflowing from the lake bottom, the existence of which are proved by CM patterns of the lake bottom sediments. The columnar samples of the lake sediments in ER-1 and ER-3-1 boreholes indicate good condition without any human tubation. The grain size character of borehole samples shows poorly sorted population, predominantly composed of fine sand and muds, varying skewness and kurtosis, which indicate multi-processed lake deposits, very similar to lake bottom sediments. Borehole columnar section, echo sounding and GPR survey profilings, as well as processed data, indicate that organic mud layers of Eurimji lake deposits are deeper and thicker towards lower bank area, especially west of profile line-9. In addition the columnar sediments indicate plant coverage of the Eurimji area were divided into two pollen zones. Arboreal pollen ( AP) is predominant in the lower pollen zone, whreas non-aboreal pollen(NAP) is rich in the upper pollen zone. Both of the pollen zones are related to the vegetation coverage frequently found in coniferous and deciduous broad-leaved trees(mixed forest) surrounded by mountains and hilly areas and prevailing by aquatic or aquatic margin under the wet temperate climate. The $^{14}C$ age of the dark gray organic muds, ER1-12 sample, is 950$\pm$40 years B.P. As the sediments are anthropogenetically undisturbed, it is assumed that the reliability of age is high. Three $^{14}C$ ages of the dark gray organic muds, including ER3-1-8, ER3-1-10, ER3-1-11 samples, are 600$\pm$30 years B.P., 650$\pm$30 years B.P., 800$\pm$40 years B.P. in the descending order of stratigraphic columnar section. Based on the interpretation of depositional environments and formation ages, it is proved that Eurimji reservoir were constructed at least 950$\pm$40 years B.P., the calibrated ages of which ranges from 827 years, B.P. to 866 years B.P. Ancient people utilize the natural environment of the stream valley to meet the need of water irrigation for agriculture in the local valley center and old alluvium fan area.