• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.743-754
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• 2000

Model parameters of the WASP5 applied to Saemanguem lake were estimated. The methodology is based on grouping water quality constituents and relevant parameters and successively estimating each group of parameters by a trial-and-error procedure. Chlorophyll-a, nitrogen cycles, phosphorus cycles, BOD and DO were simulated at the complexity level 4. The Saemangeum basin divided into a number of unit sub-watershed. And a water budget model analysis with 22 years from 1975 to 1996 year was examined. In this paper, input data at upstream boundaries of model was made to determine seasonally-averaged flow rate through water budget analysis. Calibration and verification of the model were used seasonal average of water quality measurements in 1997 and 1998 years. Grouping water quality constituents and associated parameters proved to be efficient in estimating a number of model parameters. From the results of model calibration and verification, it was found that quantitative evaluations of nonpoint source for organic matters are essential.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1223-1234
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• 2022

Efforts for reducing greenhouse gas emission coping with climate change have also been performed in the field of water and wastewater works. In particular, the technical development for reducing energy has been applied in operating water distribution system. The reduction of energy in water distribution system can be achieved by reducing structural loss induced by topographic variation and operational loss induced by leakage and friction. However, both analytical and numerical approaches for analyzing energy budget of water distribution system has been challengeable because energy components are affected by the complex interaction of affecting factors. This research drew mathematical equations for 5 types of state (hypothetical, ideal, leak-included ideal, leak-excluded real, and real), which depend on the assumptions of topographic variation, leakage, and friction. Furthermore, the derived equations are schematically illustrated and applied into simple water network. The suggested method makes water utilities quantify, classify, and evaluate the energy of water distribution system.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1112-1116
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• 2009

The importance of securing water resources and their efficient management has attracted more attention recently due to water deficit. In water budget analysis, however, evapotranspiration (${\lambda}E$) has been approximated as the residual in the water balance equation or estimated from empirical equations and assumptions. To minimize the uncertainties in these estimates, it is necessary to directly measure ${\lambda}E$. In this study, using the eddy covariance technique, we have measured ${\lambda}E$ in a mixed forest in the Seolmacheon catchment in Korea from September 2007 to December 2008. During the growing season (May - July), ${\lambda}E$ in this mixed forest averaged about 2.2 mm $d^{-1}$, whereas it was on average 0.5 mm $d^{-1}$ during the non-growing season in winter. The annual total ${\lambda}E$ in 2008 was 581 mm $y^{-1}$, which is about 1/3 of the annual precipitation of 1997 mm. Despite the differences in the amount and frequency of precipitation, the accumulated ${\lambda}E$ during the overlapping period (i.e., September to December) for 2007 and 2008 was both ${\sim}$ 110 mm, showing virtually no difference. The omega factor, which is a measure of decoupling between forest and the atmosphere, was on average 0.5, indicating that the contributions of equilibrium ${\lambda}E$ and imposed ${\lambda}E$ to the total ${\lambda}E$ were about the same. The results suggest that ${\lambda}E$in this mixed forest was controlled by various factors such as net radiation, vapor pressure deficit, and canopy conductance. In this study, based on the direct measurements of ${\lambda}E$, we have quantified the relative contribution of ${\lambda}E$in the water balance of a mixed forest in the Seolmacheon catchment. In combination with runoff data, the information on ${\lambda}E$ would greatly enhance the reliability of water budget analysis in this catchment.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.37-46
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• 2012

The change of rainfall pattern and hydrologic factors due to climate change increases the occurrence probability of agricultural reservoir water shortage. Water supply assessment of reservoir is usually performed current reservoir level compared to historical water levels or the simulation of reservoir operation based on the water budget analysis. Since each reservoir has the native property for watershed, irrigation district and irrigation water requirement, it is necessary to improve the assessment methods of agricultural reservoir water capability about water resources system. This study proposed a practical methods that water supply vulnerability assessment for an agricultural reservoir based on a concept of probabilistic reliability. The vulnerability assessment of water supply is calculated from probability distribution of water demand condition and water supply condition that influences on water resources management and reservoir operations. The water supply vulnerability indices are estimated to evaluate the performance of water supply on agricultural reservoir system, and thus it is recommended a more objective method to evaluate water supply reliability.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.447-459
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• 2000

Since the development of water resources is getting more difficult than ever before because of human-sociological condition, it would be necessary to develop a practically applicable technique for the management of water resources based on demand-side concept that could reduce unusable release for more effective and appropriate allocation of limited water resources. The objective of the study is to develop an optimal reservoir system operation model for water supply and energy augmentation by the combination of water budget analysis method in downstream area by MIP technique. The applicable study of the developed model was carried out and water supply capability of Nakdong river basin was re-evaluated by the developed model. The model has been found successful to guarantee appropriate water supply to the basin by means of deficit-supply management method and also turned out to be more practical tool for an optimal reservoir system operation model than other existing models.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1925-1930
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• 2006

A quasi depth-varying mathematical model for wind-generated circulation in coastal areas, expressed in terms of the depth-averaged horizontal velocity components and free surface elevation was validated and used to understand the diurnal circulation process. The wind velocity is considered as a dominant factor for driving the wind generated current. In this paper, three dimensional numerical experiments that included the land topography were used to investigate the mesoscale air flow over the coastal regions. The surface temperature of the inland was determined through the surface heat budget consideration with inclusion of a layer of vegetation. A series of numerical experiments were then carried out to investigate the diurnal response of the air flow and wind-generated circulation to various types of surface inhomogeneities.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.885-901
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• 2020

A forest watershed management project was introduced in 2004 to develop ecologically sound forest watersheds. It includes landslide prevention and erosion control, water resource management, landscape development, and forest resource management. However, it has been managed fragmentarily and inefficiently, far from the original intents. This study investigated current status, problems, and improvement measures of the project. Literature reviews were conducted on forest watershed management in Korea and other countries, and surveys were conducted on 201 erosion control experts. When introduced, the forest watershed management project was well planned and implemented as intended. It later turned to focus only on disaster prevention such as erosion control dams and stream conservation measures. The survey results showed that a majority (89% and 86%) of surveyees wanted increases in the project period and budget. They also responded that conflicts with local residents (51%) and determining project locations (32%) were the most difficult tasks when implementing the projects, and only 36% kept project records. To plan and implement the projects as intended, the following suggestions should be considered: (1) establishment of a solid legal foundation and improvement of the erosion control practices law; (2) increase in the project period (from 1 to 2 - 3 years) and budget; (3) development of a manual for project site selection and guidelines; (4) monitoring and systematic information management; and (5) development of spatial analysis tools for watershed analysis and management.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.123-128
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• 2012

For optimal reservoir operation and management, there are essential elements including water supply in agricultural reservoir and demand in irrigation district. To estimate agricultural water demand and supply, many factors such as weather, crops, soil, growing conditions cultivation method and the watershed/irrigation area should be considered, however, there are occurred water supply impossible duration under the influence of the variability and uncertainty of meteorological and hydrological phenomenon. Focusing on agricultural reservoir, amount and tendency of agricultural water supply and demand shows seasonally/regionally different patterns. Through the analysis of deviation and changes in the timing of the two elements, duration in excess of water supply can be identified quantitatively. Here, we introduce an approach to assessment of irrigation vulnerable duration for effective management of agricultural reservoir using time dependent change analysis of residual water supply and irrigation water requirements. Irrigation vulnerable duration has been determined through the comparison of water supply in agricultural reservoir and demand in irrigation district based on the water budget analysis, therefore can be used as an improved and basis data for the effective and intensive water management.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.97-106
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• 2015

A CCTV inspection method has been widely used to assess sewer condition and performance, but Korea lacks a proper decision support system for prioritizing sewer repair and rehabilitation (R&R). The objective of this paper is to introduce the results that we have developed in the Sewer Condition Assessment and Rehabilitation Decision-making (SCARD) Program using MS-EXCEL. The SCARD-Program is based on a standardized defect score for sewer structural and hydraulic assessment. Priorities are ranked based on risk scores, which are calculated by multiplying the sewer severity scores by the environmental impacts. This program is composed of three parts, which are decision-making for sewer condition and performance assessment, decision-making for sewer R&R priority assessment, and decision-making for optimal budget allocation. The SCARD-Program is useful for decision-makers, as it enables them to assess the sewer condition and to prioritize sewer R&R within the limited annual budget. In the future, this program logic will applied to the GIS-based sewer asset management system in local governments.

• Korean Journal of Remote Sensing
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• v.20 no.1
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• pp.1-11
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• 2004

Based on surface energy balance climatology, surface temperatures should respond to drying conditions well before plant response. To test this hypothesis, land surface temperatures (LST) derived from MODIS data were analyzed to determine how the data were correlated with climatic water balance variables and NDVI anomalies during a growing season in Western and Central Kansas. Daily MODIS data were integrated into weekly composites so that each composite data set included the maximum temperature recorded at each pixel during each composite period. Time-integrated, or cumulative values of the LST deviation standardized with mean air temperatures had significantly high correlation coefficients with SM, AE/PE, and MD/PE, ranging from 0.65 to 0.89. The Standardized Thermal Index (STI) is proposed in this study to accomplish the objective. The STI, based on surface temperatures standardized with observed mean air temperatures, had significant temporal relationships with the hydroclimatological factors. STI classes in all the composite periods also had a strong correlation with NDVI declines during a drought episode. Results showed that, based on LST, air temperature observations, and water budget analysis, NDVI declines below normal could be predicted as early as 8 weeks in advance in this study area.