• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.183-189
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• 2010

In this study long term rainfall-runoff model, developed based on SSARR, was applied to Geum river basin and its simulation results of major control points were compared with the corresponding observed channel discharges. The validities of the simulation results were examined with re-measured discharges of those control points. From the above procedure the points showing the unreliable results were found out and its principal causes are analyzed through hydrological inspection of runoff characteristics of their circumstances. Finally the simulation results were modified by the consideration of the effects by small-scale hydraulic structures which could directly affect the channel discharges. As a result the annual runoff simulations of two major points in Geum river basin, Yongdam and Daecheong dam sites, work well. However the low flow simulation of the point located between them, Sutong station, showed more or less the unreliable result. Its causes are considered by means of the hydraulic/hydrological inspection of the corresponding point.

• Journal of Korea Water Resources Association
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• v.48 no.10
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• pp.831-843
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• 2015

This study estimates MODIS-derived evapotranspiration data quality by revised RS-PM algorithm in Seolmacheon test basin. We used latent flux with eddy covariance method to evaluate MODIS-derived spatial evapotranspiration and gap-filled these data by three methods (FAO-PM, MDV and Kalman Filter) and to quantify daily evapotranspiration. Gap-filled daily evapotranspiration data was used to evaluate evapotranspiration computed by revised RS-PM algorithm derived MODIS satellite images. For the water budget analysis, we used soil moisture content that is quantified to average individual soil moisture rate observed by TDR (Time Domain Reflectometry) sensor at soil depth. The soil moisture variation is calculated in consideration from initial to final soil moisture content. According to the result of this study, evapotranspiration computed by revised RS-PM algorithm is very larger than eddy covariance data gap-filled by three methods. Also, water budget characteristics is not closed. We could analysis that MODIS-derived spatial evapotranspiration does not represent actual evapotranspiration in Seolmacheon.

• Journal of Korea Water Resources Association
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• v.53 no.6
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• pp.437-450
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• 2020

This study presents a probabilistic distributed hydrological model for Ephemeral catchment, where zero flow often occurs due to the influence of distinct climate characteristics in South Korea. The gridded hydrological model is developed by combining the Sacramento Soil Moisture Accounting Model (SAC-SMA) runoff model with a routing model. In addition, an error model is employed to represent a probabilistic hydrologic model. To be specific, the hydrologic model is coupled with a censoring error model to properly represent the features of ephemeral catchments. The performance of the censoring error model is evaluated by comparing it with the Gaussian error model, which has been utilized in a probabilistic model. We first address the necessity to consider ephemeral catchments through a review of the extensive research conducted over the recent decade. Then, the Yongdam Dam catchment is selected for our study area to confirm the usefulness of the hydrologic model developed in this study. Our results indicate that the use of the censored error model provides more reliable results, although the two models considered in this study perform reliable results. In addition, the Gaussian model delivers many negative flow values, suggesting that it occasionally offers unrealistic estimations in hydrologic modeling. In an in-depth analysis, we find that the efficiency of the censored error model may increase as the frequency of zero flow increases. Finally, we discuss the importance of utilizing the censored error model when the hydrologic model is applied for ephemeral catchments in South Korea.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.4
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• pp.52-65
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• 1984

In general precise estimation of hourly of daily distribution of the long-term run-off should be very important in a design of source of irrigation. However, there have not been a satisfying method for forecasting of stationar'y long-term run-off in Korea. Solving this problem, this study introduces unit-hydrograph method frequently used in short-term run-off analysis into the long-term run-off analysis, of which model basin was selected to be Sumgin-river catchment area. In the estimation of effective rainfall, conventional method neglects the Soil moisture condition of catchment area, but in this study, the initial discharge (qb) occurred just before rising phase of the hydrograph was selected as the index of a basin soil moisture condition and then introduced as 3rd variable in the analysis of the reationship between cumulative rainfall and cumulative loss of rainfall, which built a new type of separation method of effective rainfall. In next step, in order to normalize significant potential error included in hydrological data, especially in vast catchment area, Snyder's correlation method was applied. A key to solution in this study is multiple correlation method or multiple regressional analysis, which is primarily based on the method of least squres and which is solved by the form of systems of linear equations. And for verification of the change of characteristics of unit hydrograph according to the variation of a various kind of hydrological charateristics (for example, precipitation, tree cover, soil condition, etc),seasonal unit hydrograph models of dry season(autumn, winter), semi-dry season (spring), rainy season (summer) were made respectively. The results obtained in this study were summarized as follows; 1.During the test period of 1966-1971, effective rainfall was estimated for the total 114 run-off hydrograph. From this estimation results, relative error of estimation to the ovservation value was 6%, -which is mush smaller than 12% of the error of conventional method. 2.During the test period, daily distribution of long-term run-off discharge was estimated by the unit hydrograph model. From this estimation results, relative error of estimation by the application of standard unit hydrograph model was 12%. When estimating by each seasonal unit bydrograph model, the relative error was 14% during dry season 10% during semi-dry season and 7% during rainy season, which is much smaller than 37% of conventional method. Summing up the analysis results obtained above, it is convinced that qb-index method of this study for the estimation of effective rainfall be preciser than any other method developed before. Because even recently no method has been developed for the estimation of daily distribution of long-term run-off dicharge, therefore estimation value by unit hydrograph model was only compared with that due to kaziyama method which estimates monthly run-off discharge. However this method due to this study turns out to have high accuracy. If specially mentioned from the results of this study, there is no need to use each seasonal unit hydrograph model separately except the case of semi-dry season. The author hopes to analyze the latter case in future sudies.

• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.404-417
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• 2006

In order to clarify some characteristics of hydrological cycle in the subalpine zone of Mt. Halla, water balance has been analysed using hydrological data of a first-order drainage basin around Mansedongsan and meterological data of Odeung AWS. The experimental basin extends from 1,595 m to 1,645 m in altitude and has an catchment area of 1.34 ha. It is largely underlain by trachybasalt and covered with sasa bamboo and sedges. Hydrological observations were carried out every 20 minutes from April 15 to September 19, 2004. The basin shows the total precipitation of 3,074 m that is 1.6 to 3 times of those in coastal and intermontane regions. Surface runoff amounts to 850 mm that is equivalent to 27.6% of the precipitation. By contrast, evapotranspiration only accounts for 14.2% of the precipitation, and the remnant of 1,790 m penetrates underground through a basement. The basin is located in the subalpine zone and then it has a high rainfall intensity as well as a large rainfall due to frequent orographic precipitation. But surface runoff usually dose not exceed 30% of the rainfall while Percolation demonstrates about 2 times of the runoff. Compared with granite or gneiss basins in Korea Peninsula, the experimental basin is characterized by a higher portion of percolation in water balance. And it is probably related to the highly permeable basaltic lavas in Jeju Island which are also overlain by porous volcanic soils.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.311-320
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• 2021

The agricultural water, which occupy about 61% of total water usage in the South Korea, is significantly objective to archieve effecitive water resources management. The objective of the study is to suggest a simple method in actual practice that could be used to estimate agricultural water usage in river considering hydrological condition. Historical record of agricultural water usage and runoff, which take account for hydrological condition of the basin, were obtained for totally 27 river basins. As the result, the high threshold value of the agricultural water usage rates compared to maximum usage amount has a particular correlations to the percent of normal year runoff for last 2 month, and threshold line of agricultural water usage rates was derived using the quantile regressions. Finally, two dimensionless threshold line and empirical formulas that described the correlation between the percent of normal year runoff for last 2 month and the agricultural water usage rate compared to maximum usage amount were derived. Also, the simple criteria to select which line and formula based on the characteristics of the basins was suggested but it need further studies. The result of the study could be used as an elemantary data in actual practice for water resoureces management.

• Journal of the Korean association of regional geographers
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• v.14 no.1
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• pp.19-26
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• 2008

A validation study has been performed using the Soil and Water Assessment Tool(SWAT) model with data collected for the Neponset River watershed, which includes roughly 130 square miles of land located southwest of Boston. All of this land drains into the Neponset River, and ultimately into Boston Harbor. This paper presents the methodology of a SWAT model. The calculated contribution of the baseflow to the streamflow is far too high whereas the interflow is strongly underestimated. Alternatively, the modified and calibrated model yields far better results for the catchment. The modification allows hydrological processes to be modeled while not restraining the applicability of the model to catchments with other characteristics. For this study, the SWAT 2005 model is used with ArcGIS 9.1 as an interlace, and sensitivity analysis is performed to provide rough estimated values before adjusting sensitive input parameters during calibration period.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.317-325
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• 2010

This study was to investigate phytoplankton communities and to evaluate the effects of hydrological and physical-chemical environmental factors in major five dam reservoirs in the Han River water system. Annual average of chlorophyll a concentration in Lake Paldang, Lake Cheongpyeong and Lake Doam was higher than that of Lake Chungju and Lake Hoengseong. The opposite seasonal variation patterns of phytoplankton growth were observed in dam reservoirs; the highest biomass in spring of dry season in Lake Paldang, Lake Cheongpyeong which are the river-type reservoirs and Lake Doam where turbidity was high throughout the year, and in summer and autumn of rainy season in Lake Chungju and Lake Hoengseong which are the lake-type reservoirs, indicating that the seasonal pattern for growth of phytoplankton in on-river reservoirs is mainly determined by hydrologic characteristics. The dominant species of phytoplankton in Lake Paldang, Lake Cheongpyeong and Lake Doam, where the concentration of nutrients was relatively high, were Bacillariophyceae such as Stephanodiscus hantzschii, Aulacoseira granulata var. angustissima in Lake Paldang and Lake Cyeongpyeong and Nitzschia spp. in Lake Doam throughout all season. The dominant species of phytoplankton in Lake Chungju and Lake Hoengseong which showed the oligo-mesotrophic state, were Bacillariophyceae such as Stephanodiscus hantzschii, Cyclotella pseudostelligera in spring and winter, but Cyanophyceae such as Microcystis spp. in summer.

• Korean Journal of Remote Sensing
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• v.28 no.4
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• pp.435-448
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• 2012

Evapotranspiration (ET) including evaporation from a land surface and transpiration from photosynthesis of vegetation is a sensitive hydrological factor with outer circumstances. Though both direct measurements with an evaporation pan and a lysimeter, and empirical methods using eddy covariance technique and the Bowen ratio have been widely used to observe ET accurately, they have a limitation that the observation can stand for the exact site, not for an area. In this study, remote sensing technique is adopted to compensate the limitation of ground observation using the Moderate Resolution Imaging Spectroradiometer (MODIS) multispectral sensor mounted on Terra satellite. We improved to evapotranspiration model based on remote sensing (Mu et al., 2007) and estimated Penman-Monteith evapotranspiration considering regional characteristics of Korea that was using only MODIS product. We validated evapotranspiration of Sulma (SMK)/Cheongmi (CFK) flux tower observation and calculation. The results showed high correlation coefficient as 0.69 and 0.74.

• Ecology and Resilient Infrastructure
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• v.4 no.1
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• pp.3-11
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• 2017

In this study, change in vegetation on bars was analyzed using the data on hydrology and river morphology with on-site photographic monitoring data for the sites of interest of the Naeseong Stream during the period from March 2013 to July 2016 when the impoundment of Yeongju Dam began. The effect of flow condition on burial and removal of vegetation covered on bar surfaces was elucidated by comparison of on-site photographic monitoring data with continuous water level plotted with on the cross-section profile. In 2014 burial happened due to late flood, while July flood caused burial and removal in 2016. On the contrary vegetation increased in 2015 due to low flow without flood. Results of this study showing natural changes in vegetation will be reference to changes which is expected to be caused by dam impoundment.