• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.661-669
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• 2017

A distributed watershed model CAMEL (Chemicals, Agricultural Management and Erosion Losses) was applied to a small rural watershed where intensive livestock farming sites are located to estimate nitrate leaching rates from soil to groundwater. The model was calibrated against the stream flows, and T-N and $NO_3-N$ concentrations were observed at the watershed outlet for three rainfall events in 2014. The simulation results showed good agreement with the observed stream flows ($R^2=0.67{\sim}0.93$), T-N concentrations ($R^2=0.40{\sim}0.58$) and $NO_3-N$ concentrations ($R^2=0.43{\sim}0.65$). The estimated annual nitrate leaching rate of the watershed was 33.0 kg N/ha/yr. The contributing proportions of individual activities to the total nitrate leaching rate of the watershed were estimated for livestock farming, applications of chemical fertilizer, and manure. The simulation results showed that the highest contributor to the nitrate leaching rate of the watershed was chemical fertilizer applications. The simulation period was for one year only, however, and results may vary depending on different conditions. Gathering input data over a longer period of time and monitoring data for calibration is needed. When this has been accomplished, it is expected that this model can be applied to small rural watersheds for evaluating temporal and spatial variations of nitrogen transformations and transport processes.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.776-783
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• 2011

In a natural water body, a useful ecotechnology to reduce standing crops of phytoplankton is to strengthen the top-down force of zooplankton. However, the predation of fish for zooplankton can make the force weak. This study was conducted to find out the effect of fish on the grazing pressure of zooplankton in the mesocosms established in a eutrophic stream (Kyongan Stream) from October to November in 2010. In the corral with fish, chlorophyll a concentration increased, and a small size cladoceran Bosmina longirostris was dominant. In the corral without fish, chlorophyll a concentration decreased along with the domination of a large cladoceran Daphnia galeata and a large copepod Eudiaptomus japonicus. The size-selective predation of fish appeared to miniaturize the zooplankton community, to narrow their food-size spectrum, and to weaken the top-down force.

• Journal of Korean Society of Rural Planning
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• v.24 no.4
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• pp.37-46
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• 2018

The nonpoint pollution source (NPS) is irregular in the amount of generated and runoff. About 70% of the water pollution sources in Korea are NPS. Most of the rural areas are small towns with less than 50 families. This is where sewerage supply is poor. This is where the domestic swage of the house flows directly into the small stream. This study investigated the amount and concentration of domestic swage. And investigated NPS for public officials. We have suggested an improvement plan here. Local government officials lack the concept of NPS. Rural residents also do not know about NPS. Therefore, we proposed NPS public relations and education linked to public administration. This is an extension of the national budget and interest. The domestic swage is discharged at about 272 liters per day in a house. We proposed the introduction of small facilities. If the capacity remains, it is suggested to link to cattle shed, pigsty and so on. The BOD, COD, TN, TP, and SS concentrations were all high. This suggested a reduction in concentration in combination with natural water. Finally, NPS facilities were proposed to be put into rural areas. And it was determined that continuous monitoring was necessary. The results of this study were expected to be applied to NPS management.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.39-43
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• 2005

The dynamics of water quality with the storm events were analyzed in a small reservoir for irrigation, Lake Wangkung. Water quality of the inflowing stream fluctuated seasonally with the variation of flow rate. Thermal stratification was consistent from April to October below 2 m depths and anoxic layer was developed below 2 m depth in summer. The unique feature of temperature showed that thermal stratification was disrupted by a heavy rain event during monsoon, but hypolimnetic hypoxia were reestablished after a few days. Phosphorus and nitrogen increased immediately following storm events. The marked increase may be due to the input of P-rich storm runoff from the watershed. Internal phosphorus loading can be one of the explanations for TP increases in summer. When there was a storm, total populations of phytoplankton and zooplankton was reduced immediately following the storm, indicating possible flushing of algae and zooplankton. After a lag period of low-density the plankton population bloomed to a peak again within five days after the storm. Turbid water in lake became clear again which coincided with the time of the phytoplankton buildup. The results demonstrate that water quality is regulated greatly by rainfall intensity in Lake Wangkung.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.14-19
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• 2005

Instream flow is necessary to manage the basic function of the rivers. The evaluation method of instream flow in a big river has been studied widely, However, the study in a small river hasn't researched. In theses days the environmental function of a river becomes very important. The evaluation method and secure of instream flow are basic conditions to perform it. Especially view of stream, recreation, protection of ecology are highly demanded in a urban according to the multipurpose of river spaces. Methods for determining the instream flow in the stream were explored and examined through careful reviews and evaluations of available literatures. Development of the instream flow estimation method is based on the reviewed results and methods which can be used within the acceptable levels.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.3
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• pp.23-34
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• 2006

This study reviews the applicability of the GWLF (Generalized Watershed Loading Function) model, which is based on a loading function that requires only a relatively small amount of data, in a small agricultural watershed. The hydrological data was collected from 1996 to 2004 for a study area based on the HP#6 upper stream reservoir small watershed area. This data was then used to calibrate and verify the model. A simulation based on the model yielded $R^2$ values of $0.47\sim0.89$. This is considered to have high applicability when compared to the simulation and the observed results, which yielded relatively high values of $R^2$ for SS (Suspended Solid), TN (Total Nitrogen), and TP (Total Phosphorus) of 0.58, 0.47 and 0.62, respectively. This study provides a useful approach fur researchers selecting appropriate models to use the insufficient measuring data for rural watersheds.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.783-788
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• 1999

In this study, a decision support system (DSS) was developed to calculate optimal wastetreatment cost, treatment level and treatment quantity of various pollutants for applying for in rural basin. The DSS includes a gegraphic informatino system (GIS), relational database system (RDBS), water quality models(Loading function , WASP5), watershed pollution load calculation module(SPLC), optimal water quality management plan to satisfy the water quality regulations. The system can be modified by user to trace the optimal condition for decision. The effort was conducted to apply the developed DSS to select the for optimal water quality management plan small rural basin called Kwanri Stream.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.5
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• pp.86-96
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• 1997

The arrangement of small streams in rural area, in the past times, attached importance to the prevention of flood damage through the straightening and lining of streams. Recently, the way of small stream arrangement is introducing the idea of water friendly environment or friendly space. As a result, there has been much concern with water favorable river management model which may lead to control flood. However, it is very difficult to develop a model applicable to all types of rivers, since each river has different flow velocity, flow amount and unique ecological characteristics. In this study, photo processing technique, one of landscape simulation methods, has been adopted because it helps to visually express and comprehensively evaluate pre and post scenery and easily applicable. Some important guideline and technique for the planning of small stream landscape arrangement are mentioned in this study. The simulation system for acquiring water favorable space and arranging landscapes needs to develop database which can forecast various types of landscape. It may also be used for the bases of planning and designing river environment arrangement. Computer aided image processing system enables to make selective planning in river environment arrangement. It may also enables to develop the methods for river environment development, ecology conservation, and multipurpose space utilization. Moreover, it makes economic river arrangement by applying river environment arrangement methods relevant to geographical characteristics. There are some limitations in this study, such as shortage of exact investigation on the stream direction and velocity in landscape arrangement. Continuous monitoring and research may be required to develop techniques through the application of computer graphics and digital image processing.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.12-17
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• 2007

This study was conducted to evaluate the characteristics of nonpoint source pollutants discharge from a small rural watershed. A typical rural area in Gongju City, Korea, was selected as the research site. Water quality and quantity in streams and rainfall samples were analyzed periodically from May to October 2005. Pollutant loads were estimated from a nonpoint source pollution model (AvSWAT, Arcview Soil and Water Assessment Tool). During the rainy season, from June 26 to 30 September 2005 and the dry season, before 26 June and after 30 September 2005, biological oxygen demands and chemical oxygen demands accounted for 91.3% and 93.7% of annual load, respectively, while total-N and total-P were 97.1% and 91.1% of annual load, respectively. The observed stream flow was $66.5m^3sec^{-1}$, while simulation stream flow was $66.2m^3sec^{-1}$. That can be assumed that simulation can be used to estimate the stream flow without practical measurement. However, the runoff trend following the occurrence of a storm event was not recorded properly.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.203-213
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• 2011

Agriculture modern environments can vary due to factors such as land consolidation and ditch enhancement projects. But, these improvements projects can include cover-ing-up of irrigation ditches with concrete, increasing the drop between paddy field and drainage ditches, which might decrease the abundance and diversity of fish fauna around paddy fields. In this study, for the management of agrobiodiversity on fish in paddy fields, we installed a small-scale fishways between paddy fields and drainage ditches, and evaluated the effects on the eco-connection of the paddy fields, ditches and stream. Five fish species were recovered at the drainage ditches. The species exhibited characteristics spawning and growth based on the paddy field. The results indicate that the five fish species could ascend the paddy fields through the small-scale fishways. There are no difference of species numbers at ditches of environment-friendly agriculture paddy fields (A) and good agricultural practices (B) region, but individual numbers were higher at the B region. This result could be interpreted as indicating that ditch diversity was affected by positional properties rather than farming practices because the water flow and connection to adjacent stream of B region were better than A region. After ascertaining the fish species capable of ascending in a pre-survey of the drainage ditches, we set up small-scale fishways at the drop between paddy fields and drainage ditches. Three species of fish (Aphyocypris chinensis, Misgurnus anguillicaudatus, M. mizolepis) arrived at the paddy fields via small-scale fishways. The main movement time was from 18:00~24:00 and 00:00~06:00, indicating a preference for the night time period rather than the day period for migration. Concentrating the operation time from night to dawn seems prudent for effective management of small-scale fishways.