• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.112-126
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• 1996

This study was conducted to develop an optimal runoff bydrograph model by comparison of the peak discharge and time to peak between observed and simulated flows derived by four different models, that is, linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models under the conditions of heavy rainfalls with regionally uniform rainfall intensity in short durations at nine small watersheds. The results obtained through this study can be summarized as follows. 1. Parameters for four models including linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models were calibrated using a trial and error method with rainfall and runoff data for the applied watersheds. Regression analysis among parameters, rainfall and watershed characteristics were established for both linear time-invariant and nonlinear time-invariant models. 2. Correlation coefficients of the simulated peak discharge of calibrated runoff hydrographs by using four models were shown to be a high significant to the peak of observed runoff graphs. Especially, it can be concluded that the simulated peak discharge of a linear time-variant model is approaching more closely to the observed runoff hydrograph in comparison with those of three models in the applied watersheds. 3. Correlation coefficients of the simulated time to peak of calibrated runoff hydrographs by using a linear time-variant model were shown to be a high significant to the time to peak of observed runoff hydrographs than those of the other models. 4. The peak discharge and time to peak of simulated runoff hydrogaphs by using linear time-variant model are verified to be approached more closely to those of observed runoff hydrographs than those of three models in the applied watersheds. 5. It can be generally concluded that the shape of simulated hydrograph based on a linear time-variant model is getting closer to the observed runoff hydrograph than those of three models in the applied watersheds. 6. Simulated hydrographs using the nonlinear time-variant model which is based on more closely to the theoritical background of the natural runoff process are not closer to the observed runoff hydrographs in comparison with those of three models in the applied watersheds. Consequently, it is to be desired that futher study for the nonlinear time-variant model should be continued with verification using rainfall-runoff data of the other watersheds in addition to the review of analyical techniques.

• Journal of Korea Water Resources Association
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• v.55 no.6
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• pp.461-469
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• 2022

It is very important to ensure the reliability of dam inflow data, which is critical in planning and managing the supply and demand of water resources in a basin. However, the simple water balance model sometimes results in negative inflows and does not consider the actual inflow characteristics. In this study, to address these issues, the existing water balance formula was modified by considering evaporation which is available for calculation among other outflows. The modified water balance formula was applied to the Soyang Dam. The results showed that the rate of negative inflows decreased in the re-evaluated dam inflow data and it was possible to secure consistency for the total inflow volume. In addition, investigating the water availability in the Soyang Dam watershed based on the water balance concept considering evaporation, it was found that direct water use in the human aspect was about 60%, and the indirect water use in the natural aspect was about 40%. In drought years, it was also confirmed that the proportion of indirect use of water resources increased.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.941-953
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• 2022

In this study, monthly water use data were collected for 5 years from the 65 local governments included in the Han-river basin and a typical water usage ratios and patterns were calculated. The difference in water shortage was compared by considering the water usage patterns using the water balance and budget analysis model (MODSIM) and data base. As a result, it was confirmed that the change occurred in the range of -3.120% to +4.322% compared to the monthly constant ratio by period. In addition, when applying the patterns in the water balance model, 17 of the 28 middle watershed showed changes in the quantity of water shortage and the domestic and industrial water shortage would decrease about 8.0% during the maximum drought period. If it is applied in conjunction with predictive research on water usage patterns reflecting climate change, social and regional characteristics in the future, it will be possible to establish a more realistic water supply forecasts and a reliable national water resources plan.

• Journal of Korea Water Resources Association
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• v.57 no.2
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• pp.139-150
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• 2024

This study introduced a method of estimating water surface evaporation using the physical-based Penman combination equation (PCE) and the Penman wind function (PWF). A set of regression parameters in the PCE and PWF models were optimized by using the observed evaporation data for the period 2016-2017 in the Yongdam Dam watershed, and their effectiveness was explored. The estimated evaporation over the Deokyu Mountain flux tower demonstrated that the PWF method appears to have more improved results in terms of correlation, but both methods showed overestimation. Further, the PWF method was applied to the observed hydro-meteorological data on the surface of Yongdam Lake. The PWF method outperformed the PCE in the estimation of water surface evaporation in terms of goodness-of-fit measure and visual evaluation. Future studies will focus on a regionalization process which can be effective in estimating water surface evaporation for the ungauged area by linking hydrometeorological characteristics and regression parameters.

• Korean Journal of Environment and Ecology
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• v.26 no.6
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• pp.892-901
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• 2012

The purpose of this research was to analyze fish fauna, distribution patterns, and fish community structures in the Juksan-Weir regions of upper weir(R-UW) and lower weir(R-LW), which was constructed in 2011 on Yeongsan River watershed. Our outcomes will provide valuable information in the impact analysis of weir constructions next decades, even if the current research is limited to distributions and fauna studies of fishes. The fishes observed were 8 family and 30 species in all the sites, and the number of the species in the regions of R-UW and R-LW was 23(938 individuals) and 27(1,680 individuals), respectively, indicating greater abundance in the lower region of Juksan-Weir. Most dominant species was Opsarichthys uncirostris amurensis with relative abundance of 42%, and this species had greater abundance in the R-LW(49%) than in the R-UW(30%). Coilia nasus, was the migratory fish sampled in this region and had no differences of abundance between the two regions. The extic species observed were Carassius cuvieri, Lepomis macrochirus, and Micropterus salmoides. The two formers of Carassius cuvieri(1.2%) and Lepomis macrochirus(3.7%) dominated in the R-UW, whereas Micropterus salmoides had greater dominance in the region of R-LW. According to tolerance guild analysis, the proportion of sensitive species ranged from 0.4 to 0.5%, and that of tolerant species ranged from 65% to 70%, implying a severe pollution of nutrients and organic matters in the water body. In the mean time, according to trophic guild analysis, the proportion of carnivores(57 - 77%) was evidently higher than that of insectivores(10 - 20%), indicating a dominance of the carnivores. Especially, high abundance of the bass, exotic species, may disturb the fish overall food chain, so the efficient ecosystem management may be required for the conservation of endemic species. When we examined fish data files of last 60 years, the species of Culter brevicauda, designated as endangered species, was observed firstly in our research area and the total number was 5 individuals(0.2% of the total). So, this region observed should be conserved as a protection zone and further monitoring studies should be done in the future.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.193-204
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• 2000

In order to get some basic data on environmental friendly function by Korean organic farming, the chemical characteristics of soil were determined on 100 farm cultivating site in Paldang watershed area of Great Seoul. The EC and content of $NO_3-N$ and Av. $P_2O_5$ in topsoil(0~30cm) showed $2.30dS\;m^{-1}$, $82mg\;kg^{-1}$, $918mg\;kg^{-1}$ in the soil cultivated chinese cabbage. $2.29dS\;m^{-1}$, $86mg\;kg^{-1}$, $954mg\;kg^{-1}$ in the soil of lettuce, $1.83dS\;m^{-1}$, $66mg\;kg^{-1}$, $1114mg\;kg^{-1}$ in the soil of crown daisy. These salt accumulation(EC) and the high concentration of mineral content in topsoil such as nitrate and phosphate showed the soils of organic farming were contaminated by practice of organic farming for the maintenance strategy of soil fertility. The $NO_3-N$ and Av. $P_2O_5$ in the subsoil(30~60cm) showed $75mg\;kg^{-1}$ and $641mg\;kg^{-1}$, $72mg\;kg^{-1}$ and $466mg\;kg^{-1}$, $42mg\;kg^{-1}$ and $873mg\;kg^{-1}$ in soil cultivated chinese cabbage, lettuce and crown daisy respectively. It indicates eventually the high concentration of nitrate and phosphate in topsoil caused penetration to subsoil, and the high concentration of mineral contents in subsoil indicate the potential risk of leaching of ground water by Korean organic farming. The positive correlation at 1% between EC and $NO_3-N$, $K_2O$, T-C, $P_2O_5$ and T-N show the salt accumulation in the both soil depth of Korean organic farming were caused by minerals such as $NO_3-N$, $K_2O$, T-C, $P_2O_5$ and T-N by overuse of organic fertilizer.

• Journal of Korea Water Resources Association
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• v.47 no.6
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• pp.501-511
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• 2014

The effects of initial conditions and input values of the rainfall-runoff model were studied in the applications of a lumped concept model for flood event data extension. For the initial conditions of the rainfall-runoff model, baseflow effects and spatial distributions of saturation points ($R_{sa}$) for the storage function methods (SFM) were analyzed. In addition, researches on the effects of rainfall data conditions as input values for the rainfall-runoff model were performed. The Chungju Dam watershed was selected and divided into 3 catchments including smaller size of 22 sub-catchments. The observed discharge and inflow amounts at Yeongwol 1, Chungju Dam, and Yeongwol 2 water level stations were individually operated as criteria for flood data extension in 30 flood events from 1993 to 2009. Direct and base flow were distinguished from a stream flow. In order to test capability of flood data extension, obtained base flow was applied to the rainfall-runoff model for three water level stations. When base flow was adopted in the model, the Nash-Sutcliffe Efficiency(NSE) was increased. The numbers of over satisfaction for model performance (>0.5) were increased over 10%. Saturation points ($R_{sa}$) which strongly influence the runoff amount when rainfall starts were optimized based on the runoff amount at three water level stations. The sizes of saturation points for three locations were similar which means saturation point size is not depending on the runoff amount. The effects of rainfall information for flood runoff were tested at 2002ev1 and 2008ev1. When increased the amount of rainfall information, the runoff simulations were closer to the simulations with full of rainfall information. However, the size of improvement was not substantial on rainfall-runoff simulations in terms of the size of total amount of rainfall.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.775-782
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• 2000

Water quality models can be applied to manage the regional water quality problems and to estimate the target and allowable pollution load in watershed effectively. Since the models such as QUAL2E, W ASP5 and HSPF need many data and are not easily applied in real systems, the water quality model, which would be simple and easily applicable, has been required. Thus, an Analytical Model of BOD(AMB) considering travel time of pollutant was developed for the total pollution load regulation in drainage basin. It was found that the main stream length of a sub-basin in the AMB should be shorter than 7km and the length of distributed pollutant load should also be shorter than 3.5km in a sub-basin. The basin in the AMB could be divided into sub-basins with almost same hydraulic characteristics and reaction rate constant satisfying the proposed stream length. The running results of the AMB in a small stream were very close to the results of QUAL2E, which is widely used one in the world. Therefore, the AlVIB can be used to regulate the total pollution load in drainage district by local government.rnment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.3
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• pp.31-42
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• 1986

The probabilistic model was developed to give a spatial simlation of precipitation series to solve the problem of future need of water resources. The simulation of daily precipitation series at the sub-base stations was induced from the spatial structure of rainfall occurrence probability between the base station and the sub-base stations in the watershed. In this study Hadong was chosen as the base station in Seomjin river basin and Imsil, Boseong, Soonchang, Dongbok, and Gurye were also selected as the sub-base stations. The results of this study are as follows; 1) The separation technique of spatial precipitation state showed effectiveness in the spatial simulation method because the occurrence probability by each precipitation state (Wet-Wet, Dry-Wet, Wet-Dry, and Dry- Dry system) represented the stable value. 2) The daily precipitation series of the sub-base stations which were simulated from those of the base station showed that the simulated annual mean precipitations were similar to the observed data, but the precipitations in summer were decreased slightly. 3) The correlogram and power spectrum of the simulated monthly precipitation for the sub-base stations showed those of the observed sample with good agreement.

• Journal of Korea Water Resources Association
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• v.48 no.11
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• pp.915-923
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• 2015

A method of estimating irrigation water need based on water balance and net water consumption concept is proposed, and applied to four watersheds in order to assess the regional and altitudinal characteristics of evapotranspiration and water need for upland crops in Jeju Island. Potential and actual evapotranspiration, and net water need were calculated during the period 1992 to 2013 using SWAT-K watershed model. The annual potential evapotranspiration decreased linearly with increasing elevation, while actual evapotranspiration showed increase with elevation to 400 m around and gradual decrease at higher elevation due to vegetation species, water availability, and cold limitation. Altitudinal pattern of net water need showed linear decrease with increasing elevation for three watersheds (Han-cheon, Cheonmi-cheon, and Oedo-cheon), and annual values of net water need for upland areas (below 200 m in elevation) were 559~680mm/yr. The comparison between actual pumping rate from wells and net water need for irrigation area showed that the amount of pumping water significantly increased during summer season (June to August), while net water need for crop cultivation relatively decreased during this period. To ensure these results, more water use data from pumping wells and additional watersheds should be investigated in the next study.