• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.2
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• pp.27-35
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• 2022

Based on the current status of groundwater usage in the dry season through field surveys, this study tried to suggest countermeasures to reduce groundwater usage and to improve the water quality of baseflow from agricultural fields. For this purposes, basins with water curtain cultivation preceded were targeted where decreases of groundwater due to continuous use of groundwater in spring and winter annually observed. From monitoring groudwater usage of the study watershed, 130,058, 130,105 m³/day of water was pumped in during the water curtain cultivation period (October-February) in the Shindun, Seokwon watershed respectively. And the pilot application of the smart automated sensor-based water curtain cultivation system (smart WC system) developed in this study to reduce groundwater consumption has been conducted. As a result, the efficiency of the smart WC system when threshold temperature is set as 6.3 ℃ was 21.1% compared to conventional cultivation and efficiency increased as threshold temperature gets lower. Lastly, in this study, culvert drainage and Bio-filters were installed and rainfall monitoring was performed 15 times in order to analyze the baseflow securement and pollutant loads behavior. As a result, the test-bed with culvert drainage and Bio-filter installed together generated 61.4% more baseflow (4.974 m³) than the test-bed with only culvert drainage was installed (3.056 m³). However, the total pollutant load of all water quality contents (BOD, COD, T-N, TOC) except for the SS and T-P was found to be greater in the culvert drain and Bio-filter installed than in the culvert drain test-bed.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.65-71
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• 2010

This study was conducted to investigate the dynamics of nutrients such as total nitrogen (TN), nitrate nitrogen ($NO_3$-N) total phosphorous (TP), and phosphate phosphorous ($PO_4$-P) in outflow from a cabbage farmland in a mixed land-use watershed. The TN concentrations in groundwater showed twice peaks in late July 2006 and late March 2007 (3.8, 4.7 mg/L, respectively), when it rained shortly after fertilizer application, indicating that nitrogen leaching is greatly influenced by fertilization and rainfall. The mean concentrations of TN and $NO_3$-N in surface water were not significantly higher than those in groundwater, while the mean concentrations of TP and $PO_4$-P in surface water were significantly (p < 0.05) were higher than those in groundwater. The TN concentrations in groundwater were generally higher than those in surface water during fertilization and early growing season due to the effect of fertilization, but vice versa in the other periods. In contrast, the TP concentrations in groundwater were always lower than those in surface water due to the sorption of particulate phosphorous by soil. The ratio of TN load in baseflow to that in total TN load (39 %) was much greater than the TP ratio (7 %), suggesting that baseflow contribute to nitrogen export. Therefore, proper fertilization management should be taken to reduce nitrogen load through baseflow.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.31-43
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• 1988

The Purpose of this study is to develop the rainfall-delayed response model (RDR Model) which influences the baseflow proportion of rivers as a result of the antecedent precipitation of the previous several months. The assesment of accurate baseflows in the rivers is one of the most important elements for the planning of seasonal water supply for agriculture, water resources development, hydrological studies for the availability of water and design criteria for various irrigation facilities. The Palukan river gauging site which is located in the Pulukan catchment on Bali Island, Indonesia was selected to develop this model. The basic data which has been used comprises the available historic flow records at 19 hydrologic gauging stations and 77 rainfall stations on Bali Island in the study. The methology adopted for the derivation of the RDR model was the water balance equation which is commonly used for any natural catcbment ie.P=R+(catchment losses) -R+(ET+DP+DSM+DGW). The catchment losses consist of evapotranspiration, deep percolation. change in soil moisture, and change in groundwater storage. The catchment areal rainfall has been generated by applying the combination method of Thiessen polygon and Isohyetal lines in the studies. The results obtained from the studies may be summarized as follows ; 1. The rainfall-runoff relationship derived from the water balance equation is as shown below, assuming a relationship of the form Y=AX+B. Finally these two equations for the annual runoff were derived ; ARO$_1$=0.855 ARF-821, ARF>=l,400mm ARO$_2$=0.290ARF- 33, ARF<1,400mm 2. It was found that the correction of observed precipitation by a combination of Thiessen polygons and Isohyetal lines gave good correlation. 3. Analysis of historic flow data and rainfall, shows that surface runoff and base flow are 52 % and 48% (equivalent to 59.4 mm) of the annual runoff, respectively. 4. Among the eight trial RDR models run, Model C provided the correlation with historic flow data. The number of months over which baseflow is distributed and the relative proportions of rainfall contributing in each month, were estimated by performing several trial runs using data for the Pulukan catchment These resulted in a value for N of 4 months with contributing proportions of 0.45, 0.50, 0.03 and 0.02. Thus the baseflow in any month is given by : P$_1$(n) =0.45 P(n) +0.50 P(n-I ) +0.03 P(n-$_2$) +0.02 P(n-$_3$) 5. The RDR model test gave estimated flows within +3.4 % and -1.0 % of the observed flows. 6. In the case of 3 consecutive no rain months, it was verified that 2.8 % of the dependable annual flow will be carried over the following year and 5.8 % of the potential annual baseflow will be transfered to the next year as a result of the rainfall-delayed response. The results of evaluating the pefformance of the RDR Model was generally satisfactory.

• The Journal of Engineering Geology
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• v.21 no.2
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• pp.107-116
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• 2011

Groundwater level data and flowrate data were collected by considering the distance between the groundwater-level gauge station and flowrate gauge station (< 10 km) in the Geum River watershed, Baseflow was separated from the collected flowrate data using the WHAT SYSTEM, which is a Web- and GIS-based tool developed for hydrological applications, Correlation analysis was performed for the separated baseflow and groundwater-level data collected from a site close to the flowrate gauge station, Twenty regions were selected and data sets were collected from 2002 to 2008. Twelve regions yielded a correlation coefficient of > 0.5, When the data sets were analyzed for each year for all 20 regions, we obtained a correlation coefficient of 0.5-0.6 for 8 cases, 0.6-0.7 for 5 cases, and > 0.7 for 12 cases. For individual regions, the correlation coefficient varied from year to year. There was a tendency toward weak correlation in the case of drought or flood, Therefore, under normal conditions (i.e., neither flood nor severe drought), it is possible to estimate the baseflow from nearby groundwater-level data for regions with a high correlation coefficient.

• Water for future
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• v.29 no.6
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• pp.131-139
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• 1996

The main goal of this study is a rainfall-runoff analysis using atopographically-based distributed model. It consists of two parts: one is a direct runoff submodel and the other is a baseflow submodel. The direct runoff submodel is a distributed model which routed through the drainage networks with a kinematic wave model. The baseflow submodel is considered as a lumped system. This model makes it possible to take the effect of areal and temporal distribution of storm into accout.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.181-188
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• 2002

Water flow rate into the tunnel usually determined by numerical analyses and mathematical formulas using water levels and permeability is obtained only a few limited districts of the whole tunneling site. However, underground is not a homogeneous but complicated mass. Therefore these methods can't reflect structural and geological aspects. In this study, assuming that the mountain stream in droughty season is to be the same as baseflow of its basin, hydrological method is applied to predict the constant water flow rate into the tunnel on construction field. Prediction of constant water inflow rate is performed on each section of tunnel construction field divided into 20 sections.

• Journal of Korea Water Resources Association
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• v.37 no.5
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• pp.397-406
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• 2004

It is necessary to estimate the groundwater recharge rate properly to evaluate the reasonable development amount of groundwater in a specific site. A small basin in Wicheon River Basin located in the Province of Kyungsangbuk-Do is selected to calculate the groundwater recharge rate. Average annual groundwater recharge rates are calculated from 1992 to 1997 because wet and draught year are contained during this period. In the calculation, baseflow separation method and SCS-CN method are applied to this area. As a result of estimation by baseflow separation method, the value of groundwater recharge ratio is varied between 11.9% and 18.7%. The average annual recharge rate is 14.5%. The average annual recharge rate calculated by SCS-CN method is varied between 7.9% and 20.9%. The average annual recharge rate in the calculation period is 15.1%. The results show that the average annual recharge amount from infiltration in the study basin is 141.6mm and 147.4mm in each estimation method. It appears that the average annual recharge amount calculated for the long period containing wet and draught year by the two methods is useful for groundwater development.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.79-84
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• 2003

This study revealed the differences in runoff processes of granite drainage basins in Korea and Mongolia by hydrological measurements in the field. The experimental drainage basins are chosen in Korea (K-basin) and Mongolia (M-basin). Occurrence of intermittent flow in K-basin possibly implies that very quick discharge dominates. The very high runoff coefficient implies that most of effective rainfall quickly discharge by throughflow or pipeflow. The Hortonian overlandflow is thought to almost not occur because of high infiltration capacity originated by coarse grain sized soils of K- basin. Very little baseflow and high runoff coefficient also suggest that rainfall almost does not infiltrate into bedrocks in K-basin. Flood runoff coefficient in M-basin shows less than 1 %. This means that most of rainfall infiltrates or evaporates in M-basin. Runoff characteristics of constant and gradually increasing discharge imply that most of rainfall infiltrates into joint planes of bedrock and flow out from spring very slowly. The hydrograph peaks are sharp and their recession limbs steep. Very short time flood with less than 1-hour lag time in M-basin means that overland flow occurs only associating with rainfall intensity of more than 10 mm/hr. When peak lag time shows less than 1 hour for the size of drainage area of 1 to 10 km2, Hortonian overland flow causes peak discharge (Jones, 1997). The results of electric conductivity suggest that residence time in soils or weathered mantles of M-basin is longer than that of K-basin. Qucik discharge caused by throughflow and pipeflow occurs dominantly in K-basin, whereas baseflow more dominantly occur than quick discharge in M-basin. Quick discharge caused by Hortonian overlandflow only associating with rainfall intensity of more than 10 mm/hr in M-basin.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.648-657
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• 2006

Characteristics of water quantity and quality of the Anyangcheon were analyzed through many field measurements and the distributed hydrologic simulation model, Soil and Water Assessment Tool (SWAT). Event mean concentrations (EMCs) and baseflow mean concentrations were calculated from the data and the daily runoff were simulated by SWAT. The runoff was divided into the direct runoff and the baseflow. Using those values and quantity and quality data of release from the wastewater treatment plant (WWPT), unit loads of BOD, COD, SS, $NO_2-N$, $NO_3-N$, $NH_3-N$, and Dis-P were derived. EMCs of BOD and SS were even higher than the baseflow mean concentrations. The total runoff from October to April (7 months) of 2004 was just 13.5%, since the rainfall usually is concentrated in summer season. Futhermore BOD and SS were loaded during the event by 50.9% and 70.9%, respectively and over three quarters of total COD, $NO_2-N$, $NO_3-N$, $NH_3-N$, and Dis-P were flowed into the Anyangcheon during the remaining period. Therefore, the efficiency of WWPT for COD, $NO_2-N$, $NO_3-N$, $NH_3-N$, and Dis-P should be intensified from Oct. to Apr. and the runoff quality management of BOD and SS should be planned during the summer season.

• Journal of Korea Water Resources Association
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• v.32 no.4
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• pp.417-426
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• 1999

A series of numerical experiments is performed to compare the characteristics of outflow hydrograph using linear and nonlinear Muskingum-Cunge methods for two cases: (a) sinusoidal inflow hydrographs and (b) rainfall inputs. The nonlinear method shows the steepening of the rising limb, coupled with a corresponding flattening of the receding limb. The linear method conserves mass exactly. In contrast, the nonlinear method is subject to a gain and a loss of mass. The loss of mass and the subsidence of peak outflow increases with a mild slope, a small baseflow $q_b$ and a large peak inflow to baseflow ratio $q_p/q_b$. A shock wave and associated numerical instability results in the increase of mass for a steep slope and a large $q_p/q_b$ ratio. While the linear method depends on the reference flow per unit-width, the nonlinear method depends on a baseflow and the $q_p/q_b$ ratio. It is found that, unlike for the sinusoidal inflow, the outflow for the rainfall inputs conserves mass fairly exactly in the nonlinear method.