• Journal of Korea Water Resources Association
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• v.52 no.1
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• pp.51-60
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• 2019

The major purpose of this study is to construct an in-situ soil moisture verification network employing Frequency Domain Reflectometry (FDR) sensors for Cosmic-ray soil moisture observation system operation as well as long-term field-scale soil moisture monitoring. The test bed of Cosmic-ray and FDR verification network system was established at the Sulma Catchment, in connection with the existing instrumentations for integrated data provision of various hydrologic variables. This test bed includes one Cosmic-ray Neutron Probe (CRNP) and ten FDR stations with four different measurement depths (10 cm, 20 cm, 30 cm, and 40 cm) at each station, and has been operating since July 2018. Furthermore, to assess the reliability of the in-situ verification network, the volumetric water content data measured by FDR sensors were compared to those calculated through the core sampling method. The evaluation results of FDR sensors- measured soil moisture against sampling method during the study period indicated a reasonable agreement, with average values of $bias=-0.03m^3/m^3$ and RMSE $0.03m^3/m^3$, revealing that this FDR network is adequate to provide long-term reliable field-scale soil moisture monitoring at Sulmacheon basin. In addition, soil moisture time series observed at all FDR stations during the study period generally respond well to the rainfall events; and at some locations, the characteristics of rainfall water intercepted by canopy were also identified. The Temporal Stability Analysis (TSA) was performed for all FDR stations located within the CRNP footprint at each measurement depth to determine the representative locations for field-average soil moisture at different soil profiles of the verification network. The TSA results showed that superior performances were obtained at FDR 5 for 10 cm depth, FDR 8 for 20 cm depth, FDR2 for 30 cm depth, and FDR1 for 40 cm depth, respectively; demonstrating that those aforementioned stations can be regarded as temporal stable locations to represent field mean soil moisture measurements at their corresponding measurement depths. Although the limit on study duration has been presented, the analysis results of this study can provide useful knowledge on soil moisture variability and stability at the test bed, as well as supporting the utilization of the Cosmic-ray observation system for long-term field-scale soil moisture monitoring.

• Journal of Korea Water Resources Association
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• v.50 no.5
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• pp.303-313
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• 2017

In environmental impact assessments for large urban development projects, the Korean government requires analysis of stormwater runoff before, during and after the projects. Though hydrological models are widely used to analyze and prepare for surface runoff during storm events, accuracy of the predicted results have been in question due to limited amount of field data for model calibrations. Intensive field measurements have been made for storm events between July 2015 and July 2016 at a sub-basin of the Gwanpyung-cheon, Daejeon, Republic of Korea using an automatic monitoring system and also additional manual measurements. Continuous precipitation and surface runoff data used for utilization of SWMM model to predict surface runoff during storm events with improved accuracy. The optimal values for Manning's roughness coefficient and values for depression storage were estimated for pervious and impervious surfaces using three representative infiltration methods; the Curve Number Methods, the Horton's Method and the Green-Ampt Methods. The results of the research is expected to be used more efficiently for urban development projects in Korea.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.3 no.2
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• pp.53-65
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• 2000

The objectives of this study are to develop a stormwater management system that would contribute to improving water circulation, recycling storm water and promoting biodiversity in urban areas, to apply the system in an actual site, and to verify its effectiveness in order to generate a stormwater management system applicable in Korea. This study reviewed former researches and case studies, categorized stormwater management system into pre-treatment, retention and infiltration phases, and analyzed the strength and weakness of the techniques by synthesizing unit techniques of each stage. As a result, the process of the stormwater management system includes the following phases: 1) a rubble filtration layer; 2) a retention pond; 3) a infiltration pond; and 4) a stormwater retention pool (recirculation and recycling). Then, an empirical study to design and create the generated system according to the features of a site and to verify its effectiveness was conducted. The future study direction is to verify the effectiveness of the developed stormwater retention and infiltration ponds. To this end, it is planned to perform hydrological monitoring using automatic measuring equipment and monitoring on habitat bases and the biota living on the base. Based on its outcome, the applied model would be refined and improved to develop an alternative stormwater management system that would allow to achieve the improvement of urban water circulation, increase of biodiversity and efficient use of water resources.

• Spatial Information Research
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• v.23 no.6
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• pp.31-41
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• 2015

This research is primarily intended to explore a novel way to monitor desiccation of inland wetland by combining MNDWI (Modified Normalized Difference Water Index) and NDVI (Normalized Difference Vegetation Index). The changes for vegetation and water condition on Upo Wetland located at southeastern Korea were investigated by MNDWI and NDVI derived from 2002, 2010 and 2015 Landsat data. The integrated use of MNDWI and NDVI made it possible to identify area-wide vegetation cover changes and to assess water storage changes on multi-annual time scales simultaneously. Comparing MNDWI with NDVI reveals the quantitative evidences for anthropogenic and environmental influences (such as road, building, water) causing an accelerated wetland desiccation. In fact, our monitoring approach raises critical issues regarding the hydrological cycle and its inter-annual changes for inland wetland under threat of drying up and highlights the important role of MNDWI and NDVI integration for any urgent or long-term treatment plan. This research presents scientific and objective evidences to support integrated approach of NDVI and MNDWI in exploring drying up trends of wetlands.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1145-1149
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• 2006

The typhoon Rusa passed through the Korean peninsula from the west-southern part to the east-northern part in the summer season of 2002. The flash flood due to the Rusa was occurred over the Korean peninsula and especially the damage was concentrated in Kangnung, Yangyang, Kosung, and Jeongsun areas of Kangwon-Do. Since the latter half of the 1990s the flash flood has became one of the frequently occurred natural disasters in Korea. Flash floods are a significant threat to lives and properties. The government has prepared against the flood disaster with the structural and nonstructural measures such as dams, levees, and flood forecasting systems. However, since the flood forecasting system requires the rainfall observations as the input data of a rainfall-runoff model, it is not a realistic system for the flash flood which is occurred in the small basins with the short travel time of flood flow. Therefore, the flash flood forecasting system should be constructed for providing the realistic alternative plan for the flash flood. To do so, firstly, Flash Flood Monitoring and Prediction (FFMP) Model must be developed suitable to Korea terrain. In this paper, We develop the FFMP model which is based on GIS, Radar techniques and hydro-geomorphologic approaches. We call it the F2MAP model. F2MAP model has three main components (1) radar rainfall estimation module for the Quantitative Precipitation Forecasts (QPF), (2) GIS Module for the Digital terrain analysis, called TOPAZ(Topographic PArametiZation), (3) hydrological module for the estimation of threshold runoff and Flash Flood Guidance(FFG). For the performance test of the model developed in this paper, F2MAP model applied to the Kangwon-Do, Korea, where had a severe damage by the Typhoon Rusa in August, 2002. The result shown that F2MAP model is suitable for the monitoring and the prediction of flash flood.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.657-665
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• 2012

The development projects distort the natural water circulation system and increase the non-point source pollution by changing the natural cover type. The low impact development (LID) techniques are considering as new development approach to decrease the ecological- and hydrological impacts from high imperviousness rate. The high imperviousness rate is because of the construction of building, parking lot and road for human activities. Knowing the basic characteristics of rood runoff can give the direction for setting up the water management strategy. The monitoring results show the pollutant EMCs of roof runoff are 3~13 times lower than EMCs of the road and parking lot. The pollutant sources from roof runoff are mainly from leafs, cigarette butts, atmospheric deposition and materials of the roof. The EMC is occurred around 15minutes later after starting runoff and more than 8 storm events are needed to have the average EMCs.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.5
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• pp.29-40
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• 2018

Even if a small amount of arsenic (As) is entering to small agricultural reservoir from upper streams, small agricultural reservoir becomes sensitive to changes in arsenic concentration depending on the water level in case of accumulation continuously because of its scale. If we want to manage arsenic concentration in small agricultural reservoir, it is very important to understand arsenic changes in agricultural reservoir. In spite of the fact that modeling is the most accurate method for analyzing arsenic concentration changes in small agricultural reservoirs, but, it is difficult to monitor arsenic change everyday. So, if data is prepared for modeling arsenic changes, water quality modeling is more effective than monitoring. Therefore, in this study, arsenic concentration changes was simulated and arsenic concentration change mechanism in small reservoir was analyzed using hydrological and water quality monitoring data and by conducting EFDC (Environment Fluid Dynamics Code)-WASP (Water Quality Analysis Simulation Program) linkage. EFDC-WASP coupling technique was very useful for modeling arsenic changes because EFDC can consider hydrodynamic and WASP can perform arsenic concentration simulation, separately. As a results of this study, during dry season, As concentration was maintained relatively high arsenic concentrations. Therefore, water level control will be needed for managing As concentration of reservoir.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.962-964
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• 2003

In 2002 Thailand was faced with severe flooding in the North, Northeast and Central parts of the country caused by heavy rainfall of the monsoonal depression which brought about significant damages. According to the report by the Ministry of Interior and the Ministry of Agricultural and Co-operatives, the total damages were estimated to be about 6 billion bath. More than 850,000 farmers and 10 million livestock were effected. An area of 1,450,000 ha of farmland in 59 Provinces were put under water for a prolonged period. Satellite imageries were employed for mapping and monitoring the flood-inundated areas, flood damage assessment, flood hazard zoning and post-flood survey of river configuration and protection works. By integrating satellite data with other updated spatial and non-spatial data, likely flood zones can be predicted beforehand. Some examples of satellite data application to flood dis aster mitigation in Thailand during 2002 using mostly Radarsat-1 data and Landsat-7 data were illustrated and discussed in the paper. The results showed that satellite data can clearly identify and give information on the status, flooding period, boundary and damage of flooding. For comprehensive flood mitigation planning, other geo-informatic data, such as the elevation of topography, hydrological data need to be integrated. Ground truth data of the watershed area, including the water level, velocity, drainage pattern and direction were also useful for flood forecasting in the future.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.218-237
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• 2018

The purpose of this study is to propose a mid - range low - orbit water disaster monitoring satellite development plan to revolutionize water disaster management infrastructure through securing an independent and leading observation infrastructure and to secure safety against disaster prepared for climate change. Water and water disaster satellites should be able to detect changes in the surface of the ground and observe hydrological factors during daytime, nighttime, and bad weather. In addition, independent technology development should be possible. To do this, we selected C-band image radar payload considering domestic technology and water resources management, and suggested detailed development plan. In this way, it is reflected in the national next-generation mid-satellite 2-phase project plan to secure the basis for building a disaster monitoring system related to wide-area water.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.699-709
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• 2011

The uses of multi-dimensional hydrodynamic and water quality models are increasing to support a sustainable management of large dam reservoirs in Korea. Any modeling study requires selection of a proper spatial dimension of the model based on the characteristics of spatial variability of concerned simulation variables. For example, a laterally averaged two-dimensional (2D) model, which has been widely used in many large dam reservoirs in Korea, assumes that the lateral variations of hydrodynamic and water quality variables are negligible. However, there has been limited studies to give a justification of the assumption. The objectives of this study were to present the characteristics of spatial variations of water quality variables through intensive field monitoring in Daechung Reservoir, and provide information on a proper spatial dimension for different water quality parameters. The monitoring results showed that the lateral variations of water temperature are marginal, but those of DO, pH, and conductivity could be significant depending on the hydrological conditions and local algal biomass. In particular, the phytoplankton (Chl-a) and nutrient concentrations showed a significant lateral variation at R2 (Daejeongri) during low flow periods in 2008 possibly because of slow lateral mixing of tributary inflow from So-oak Stream and wind driven patchiness.