• Journal of Korean Society on Water Environment
• /
• v.28 no.3
• /
• pp.375-383
• /
• 2012

Soil erosion has been emphasized as serious environmental problem affecting water quality in the receiving waterbodies. Recently, Best Management Practices (BMPs) have been applied at a field to reduce soil erosion and its effectiveness in soil erosion reduction has been monitored with various methods. Although monitoring at fields/watershed outlets would be accurate way for these ends, it is not possible at some fields/watersheds due to various limitations in direct monitoring. Thus modeling has been suggested as an alternative way to evaluate effects of the BMPs. Most models, which have been used in evaluating hydrology and water quality at a watershed, could not reflect rainfall intensity in runoff generation and soil erosion processes. In addition, source codes of these models are not always public for modification/enhancement. Thus, runoff-sediment evaluation system using hourly rainfall data and vegetated filter strip (VFS) evaluation module at field level were developed using open source MapWindow GIS component in this study. This evaluation system was applied to Bangdongri, Chuncheonsi to evaluate its prediction ability and VFS module in this study. The NSE and $R^2$ values for runoff estimation were 0.86 and 0.91, respectively, and measured and simulated sediment yield were 15.2 kg and 16.5 kg indicating this system, developed in this study, can be used to simulate runoff and sediment yield with acceptable accuracies. Nine VFS scenarios were evaluated for effectiveness of soil erosion reduction. Reduction efficiency of the VFS was high when sediment inflow was small. As shown in this study, this evaluation system can be used for evaluation BMPs with local rainfall intensity and variations considered with ease-of-use GIS interface.

• Journal of Korean Clinical Nursing Research
• /
• v.15 no.1
• /
• pp.43-53
• /
• 2009

Purpose: This study aimed to compare the moisturizing effect of cold water gargling, wet gauze application and humidification in reducing thirst and mouth dryness after nasal surgery. Method: Patients were randomly assigned into three groups of 19 subjects each. In the two intervention groups, each group was received hourly cold water gargling or wet gauze application for 4 hours postoperatively. In the control group, the subjects were received only humidification continuously on a bedside. We compared the thirst and oral condition at 0, 2, 4hours. after operation. Thirst was measured using VAS questionnaire, and oral condition(mouth dryness) by Oral Assessment Guide. Results: There was a significant difference among three groups in the level of thirst and mouth dryness. In the cold water gargling group, there was a significant decrease in thirst at 2, 4hours. In the wet gauze group, there was a significant decrease in thirst at 4hours. In the intervention group, there was a significant decrease in mouth dryness at 2, 4hours. In the control group, there was a significant decrease in mouth dryness at 4hours. Conclusion: The findings of this study suggest that the cold water gargling would be an effective nursing intervention to reduce thirst and mouth dryness postoperatively.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1611-1615
• /
• 2006

The purpose of this study is to simulate the riverbed profile changes downstream of Daecheong re-regulation dam from 1988 to 2001, to evaluate the model's applicability and to predict a long-term riverbed-level variation between 2002 and 2017. As a result of simulation 14 sediment transport equations provided by GSTAR-1D, it was found that Acker's & White formula was the most stable relatively. The interval used to calculate its stability was 7 days for bankful discharge$(1,000m^2/s)$, 3 days for daily maximum flow$(4,273m^2/s)$, 1 day for hourly maximum flow$(7,605m^2/s)$ and minimum flow$(8.5m^2/s)$. The simulation results of river bed changes were evaluated and compared to its measure data from 1988 to 2001. It was showed that there was the degradation for a section between Daecheong re-regulation dam and Maepo water stage gage station due to bed-material, and the degradation for a reach between Maepo and Gongju water stage gage station due to massive aggregate collection. Also, as a result of simulating the river profile change for 2002 to 2017, it was predicted that the section between Daecheong re-regulation dam and Geumnam Bridge would remain as the present profile and the reach between Maepo and Gongju water stage gage station would have some degradations in several parts, which would be stable as a whole unless it was due to artificial river profile change.

• Journal of Korean Society on Water Environment
• /
• v.39 no.1
• /
• pp.1-8
• /
• 2023

Monitoring and prediction of water quality are essential for effective river pollution prevention and water quality management. In this study, a multi-classification model was developed to predict chlorophyll-a (Chl-a) level in rivers. A model was developed using CatBoost, a novel ensemble machine learning algorithm. The model was developed using hourly field monitoring data collected from January 1 to December 31, 2015. For model development, chl-a was classified into class 1 (Chl-a≤10 ㎍/L), class 2 (10<Chl-a≤50 ㎍/L), and class 3 (Chl-a>50 ㎍/L), where the number of data used for the model training were 27,192, 11,031, and 511, respectively. The macro averages of precision, recall, and F1-score for the three classes were 0.58, 0.58, and 0.58, respectively, while the weighted averages were 0.89, 0.90, and 0.89, for precision, recall, and F1-score, respectively. The model showed relatively poor performance for class 3 where the number of observations was much smaller compared to the other two classes. The imbalance of data distribution among the three classes was resolved by using the synthetic minority over-sampling technique (SMOTE) algorithm, where the number of data used for model training was evenly distributed as 26,868 for each class. The model performance was improved with the macro averages of precision, rcall, and F1-score of the three classes as 0.58, 0.70, and 0.59, respectively, while the weighted averages were 0.88, 0.84, and 0.86 after SMOTE application.

• Journal of Korea Water Resources Association
• /
• v.49 no.7
• /
• pp.579-588
• /
• 2016

Changes in precipitation due to climate change is made to induce the local and intensive rainfall, it is increasing damage caused by inland inundation. Therefore, it requires a technique for predicting damage caused by flooding. In this study, in order to determine whether this flood inundated by any route when the levee was destroyed, Which can simulate the path of the flood inundation model was developed for the SIMOD (Simplified Inundation MODel). Multi Direction Method (MDM) for differential distributing the adjacent cells by using the slope and Flat-Water Assumption (FWA)-If more than one level higher in the cell adjacent to the cell level is the lowest altitude that increases the water level is equal to the adjacent cells- were applied For the evaluation of the model by setting the flooding scenarios were estimated hourly range from the target area. SIMOD model can significantly reduce simulation time because they use a simple input data of topography (DEM) and inflow flood. Since it is possible to predict results within minutes, if you can only identify inflow flood through the runoff model or levee collapse model. Therefore, it could be used to establish an evacuation plan due to flooding, such as EAP (Emergency Action Plan).

• Korean Journal of Agricultural Science
• /
• v.50 no.3
• /
• pp.331-347
• /
• 2023

The downstream submergence damages caused during the flood season in 2020, around the Yongdam-dam and five other sites, were analyzed using related dam management data. Hourly- and daily-data were collected from public national websites and to conduct various analyses, such as autocorrelation, partial-correlation, stationary test, trend test, Granger causality, Rescaled analysis, and principal statistical analysis, to find the cause of the catastrophic damages in 2020. The damage surrounding the Yongdam-dam in 2020 was confirmed to be caused by mis-management of the flood season water level. A similar pattern was found downstream of the Namgang- and Hapcheon-dams, however the damage caused via discharges from these dams in same year is uncertain. Conversely, a different pattern from that of the Yongdam-dam was seen in the areas downstream of Sumjingang- and Daecheongdams, in which the management of the flood season water level appeared appropriate and hence, the damages is assumed to have occurred via the increase in the absolute discharge amount from the dams and flood control capacity leakage of the downstream river. Because of the non-stationarity of the management data, we adapted the wavelet transform analysis to observe the behaviors of the dam management data in detail. Based on the results, an increasing trend in the discharge amount was observed from the dams after the year 2000, which may serve as a warning about similar trends in the future. Therefore, additional and continuous research on downstream safety against dam discharges is necessary.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.315-315
• /
• 2017

In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.

• Economic and Environmental Geology
• /
• v.38 no.1
• /
• pp.79-89
• /
• 2005

Groundwater level changes in coastal aquifers occur due to oceanic tides, where the properties of oceanic tides can be applied to estimate hyadraulic parameters. Hydraulic parameters of coastal aquifers located in eastern part of Jeju island were estimated using the tidal response technique. Groundwater level data from a saltwater intrusion monitoring well system was used which showed tidal effects from 3 to 5 km. The hydraulic gradient was assessed by utilizing the filtering method from 71 consecutive hourly water-level observations. Calculated hydraulic diffusivity ranged from 2.94${\times}10^7m^2d^{-1}$ to 4.36${\times}10^7m^2d^{-1}$ . The hydraulic gradient of the coastal aquifer area was found to be ~$10^{-4}$, whereas the gradient of the area between wells Handong-1 and 2 was found to be ~$10^{-6}$, which is very low comparatively. Analysis of groundwater monitoring data showed that groundwater levels are periodically higher near coastal areas compared to that of inner land areas due to oceanic tide influences. When assessing groundwater flow direction in coastal aquifers it is important to consider tidal fluctuation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.26 no.6
• /
• pp.567-579
• /
• 1993

The response of sea levels to a typhoon in the north Japanese coast in the Japan Sea is investigated by using hourly ses level data($1966{\sim}1986$) and a numerical shallow water model with high resolution($5'{\times}5'$). The observed sea level analysis shows (1) progressive waves exist between Simonoseki(SS) and Maizuru(MZ) with the mean phase speed of about 4 m/s during the passage of the typhoon, (2) the phase speed between Sasebo(SB) and HK(Hakata) is slower(about 1.7 m/s), and (3) the maximum sea level at HK is achieved about 0.5 day later than that of SS. In many aspects, the numerical model results correspond well to the above observed features. In the model the progressive waves are identified as a topographic wave with the phase speed of about 4 m/s. Before the typhoon passes through the Korea Strait/ the Tsushima Strait, the wave propagations along the Japanese coast are significantly influenced by the southwestward coastal jet induced by the wind stress parallel to the coast. The waves start to propagate northeastward along the coast when the coastal jet is weakened.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.22 no.4
• /
• pp.299-311
• /
• 2020

This paper analyzes the distribution of water vapor pressure and relative humidity in complex terrains by collecting weather observation data at 6 locations in the valley in Jungdae-ri, Ganjeon-myeon, Gurye-gun, Jeolla South Province and 14 locations in Akyang-myeon, Hadong-gun, Gyeongsang South Province, which form a single drainage basin in rural and mountainous regions. Previously estimated water vapor pressure used in the early warning system for agrometeorological hazard and actual water vapor pressure arrived at using the temperature and humidity that were measured at the highest density (1.5 m above ground) at every hour in the valley of Jungdae-ri between 19 December 2014 and 23 November 2015 and in the valley of Akyang between 15 August 2012 and 18 August 2013 were compared. The altitude-specific gradient of the observed water vapor pressure varied with different hours of the day and the difference in water vapor pressure between high and low altitudes increased in the night. The hourly variations in the water vapor pressure in the weather stations of the valley of Akyang with various topographic and ground conditions were caused by factors other than altitude. From the observed data of the study area, a coefficient that adj usts the variation in the water vapor pressure according to the specific difference in altitude and estimates it closer to the actual measured level was derived. Relative humidity was simulated as water vapor pressure estimated against the saturated water vapor pressure, thus, confirming that errors were further reduced using the derived coefficient than with the previous method that was used in the early warning system.