• Journal of Soil and Groundwater Environment
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• v.22 no.3
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• pp.18-26
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• 2017

The increasing frequency of droughts has been increasing the necessity of utilizing subsurface dams as reliable groundwater resources in areas where it is difficult to supply adequate agricultural water using only surface water. In this study, we analyzed the current status and actual conditions of five agricultural subsurface dams as well as the effect of obtaining additional groundwater from subsurface dams operated as one aspect of the sustainable integrated water management system. Based on the construction methods and functions of each subsurface dam, the five subsurface dams are classified into three types such as those that derive water from rivers, those that prevent seawater intrusion, and those that link to a main irrigation canal. The classification is based on various conditions including topography, reservoir location, irrigation facilities, and river and alluvial deposit distributions. Agricultural groundwater upstream of subsurface dams is obtained from four to five radial collector wells. From the study, the total amount of groundwater recovered from the subsurface dam is turned out to be about 29~44% of the total irrigation water demand, which is higher than that of general agricultural groundwater of about 4.6%.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.3
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• pp.15-23
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• 2024

Subsurface drainage improves crop productivity in poorly drained soils but may also substantially contribute impairment of surface water quality due to excess leaching losses of nutrients like Nitrate-Nitrogen (NO₃-N). This research presents preliminary findings from a 3-years tile depth and spacing study in Illinois state that includes three drain spacings implemented in 2 plots. We found that the plot with the narrower subsurface drainage (Case 1) exported more drainage water compared to the plot with the narrower subsurface drainage system (Case 2). The total drainage water from Case 1 plot showed 57% more compared to Case 2 plot. Whereas we observed that the plot with narrower drain spacing (Case 1) exported only 9% more NO₃-N leaching losses compared to the wider plot (Case 2). The average corn yield was observed higher in plot Case 1 compared to Case 2. Especially, we observed about 7% higher corn yield in plot Case 1 compared to Case 2 plot in the relatively dried year (2022). The preliminary findings for this study suggest that subsurface drainage systems can be optimized to reduce nutrient losses while improving the crop productivity.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.2
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• pp.3-13
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• 2007

The primary objective of this study was to compare water use efficiencies between subsurface drip irrigation and furrow irrigation. The uniformity of used drip lines was tested to determine if clogging would be a threat to the long-term success of a subsurface drip irrigation system. Three crops, cantaloupe, lettuce, and bell pepper, were grown in four plots for each irrigation system. Significantly less water was applied with subsurface drip irrigation than with furrow irrigation (29.5 % less for cantaloupe and 43.2 % less for bell poppet) in order to produce similar crop yields. Water use efficiencies with subsurface drip irrigation were significantly higher than those with furrow irrigation fur cantaloupe (P-value = 0.018) and bell pepper (P-value ${\leq}$ 0.001). Drip-irrigated lettuce, a shallow-rooted crop, had moderately higher water use efficiency during the first two seasons, while no difference was observed in the third season. After the experiment, the uniformity of the drip lines was 92.1 % on average and classified as good. The high values fur water use efficiency and uniformity indicate that subsurface drip irrigation can be a sustainable method for conserving irrigation water.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1188-1191
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• 1998

Detailed estimation of subsurface resistivity distribution and accurate estimation of actual fault current coming into the grounding system are indispensible to optimun grounding system design. Especially, it is essential for efficient grounding design to estimate subsurface resistivity distribution quantitatively and logically. Accurate estimation of subsurface resistivity distribution has an absolute influence on calculating touch voltage, step voltage and ground potential rise (GPR) which are related with grounding design standard for human safety. In this study, thirty-three electrical sounding surveys were made in Yongdam Power Station to obtain detailed subsurface resistivity distribution and the sounding data were interpreted quantitatively using multi-layered model. The results of the quantitative resistivity models were adopted practically to calculate grounding resistance values. Analytical asymptotic equations and CDEGS program were used in grounding resistance calculation and the results were compared and reviewed in the study.

• Korean Journal of Agricultural Science
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• v.47 no.2
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• pp.263-273
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• 2020

With the change of the agricultural environment (increased rice production, decreased rice consumption, and rice production policies), converting paddy fields into upland fields is an increasing trend. In terms of conversion into upland fields, subsurface drainage is one of the most important factors for good field crop growth. This study evaluates the performance of a subsurface drainage culvert system in paddy fields and reclaimed lands. The obtained results are briefly summarized as follows: 1) After a comparative evaluation of several subsurface drainage culvert systems, including excavated subsurface drainage and non-excavated subsurface drainage types, type 3 (non-excavated, perforated drain pipe 50 mm, filter mat B50 cm, subsoiling 70 cm and culvert spacing 5 m) shows relatively high values among four types in terms of effectiveness (subsurface discharge capability) and economic efficiency (construction cost). 2) Type 3 has proven that it is suitable for design standards of discharge capacity through field tests performed in paddy fields (three sites: Gong-geom, Gae-san, Juk-san) and reclaimed lands (two sites: Gum-ho, Mi-am). 3) In the experiment of Sesamum indicum growth according to the existence of a drainage system, Sesamum indicum growth with a subsurface drainage culvert system had good value in terms of plant shoot and root length, shoot fresh and dry weight, and root fresh and dry weight).

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1582-1596
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• 2005

Groundwater flow and behavior have to be investigated based on heterogeneous subsurface formation since the homogeneity assumption of this formation is not valid. Over the past twenty years, stochastic approach and Monte Carlo technique have been utilized very efficiently to understand the groundwater flow behavior. However, these techniques require lots of computational and numerical efforts according to the various researchers' comments. Therefore, utilizing new techniques with much less computational efforts such as Artificial Neural Network (ANN) in the prediction of the stochastic behavior for the groundwater based on heterogeneous subsurface formation is highly appreciated. The current paper introduces the ANN technique to investigate and predict the stochastic behavior of a well draw down in a confined aquifer based on subsurface heterogeneous hydraulic conductivity. Several ANN models are developed in this research to predict the unsteady two dimensional well draw down and its stochastic characteristics in a confined aquifer. The results of this study showed that ANN method with less computational efforts was very efficiently capable of simulating and predicting the stochastic behavior of the well draw down resulted from the continuous constant pumping in the middle of a confined aquifer with subsurface heterogeneous hydraulic conductivity.

• Current Research on Agriculture and Life Sciences
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• v.30 no.2
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• pp.97-104
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• 2012

Over the last century, drainage systems have become an integral component of agriculture. Climate observations and experiments using General circulation models suggest an intensification of the hydrologic cycle due to climate change. This study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage in Daegu, Republic of Korea. Historical and Long Ashton Research Station weather generator perturbed future climate data from 15 general circulation models for a field in Daegu were ran into a water management simulation model, DRAINMOD. The trends and variability in rainfall and Soil Excess Water ($SEW_{30}$) were assessed from 1960 to 2100. Rainfall amount and intensity were predicted to increase in the future. The predicted annual subsurface drainage flow varied from -35 to 40 % of the baseline value while the $SEW_{30}$ varied from -50 to 100%. The expected increases in subsurface drainage outflow require that more attention be given to soil and water conservation practices.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.167-176
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• 1998

On steep hillslopes, saturation zone formations and subsurface flows were monitored through the observation systems of observation wells, tensiometers and trenches. By the 103 mm rain which had fallen on the hillslope with dry soil moisture, the saturation zone began to be formed at the top of hillslope during the rain and developed to be formed within a few hours after the end of rain on all hillslope. Subsurface water outflowed mainly from the soil profile of 0-40 cm depth, but did not outflow from the one of 40-80 cm depth. This saturation zone seemed to be formed by partially saturation of soil. This resulted for two reasons. Firstly, the saturation zone was formed by a smaller amount of rain than that required. Secondly the soil at a certain depth below the water table was unsaturated. Saturation zones formed by pre-rains responded rapidly to rains and subsurface water outflowed mainly from the soil profile of 40-80 cm depth simultaneously with the rising of the water level. The rates of subsurface discharge from the soil profile of 40-80 cm depth to the precipitation were related to the antecedent precipitation although the maximum water levels of saturation zone formed by four rains were similar.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.181-192
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• 2009

In this study, the hydrological properties of permeable pavement were analyzed by the experiment and the numerical simulation. The numerical model used was a modified SWMM especially for considering the hydrological response of permeable pavement. The parameters of modified SWMM were revised by the experimental results, and then the practicability was evaluated through the comparison of the experimental and numerical simulation results. In the experiments, three different rainfall intensities such as 65 mm/hr, 90 mm/hr, 95 mm/hr were supplied for 4 hrs, and the hydraulic properties including surface outflow, subsurface outflow, ground water level, soil water contents were measured for 10 hrs. The results showed rainfall intensity effected directly on surface outflow volume and subsurface outflow volume was more effected by ground water level than rainfall intensity. The ground water level and the soil water contents were under estimated as compared with the experimental data except the portion of occurring direct runoff. The surface and subsurface outflow discharge were simulated very well in comparison with the experimental data. Consequently, the modified SWMM could be used very effectively to evaluate the hydrological property of permeable pavement.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.51-56
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• 2005

To understand the chemical changes in the streamwater and contribution of subsurface discharge during the storm event, we analyzed electric conductivity (EC), anions, and cations in Gwangneung deciduous and coniferous forest catchment. The stream water samples were collected three times in 2004 by using an auto-sampler: September 7-9 (E040907-D and -C; where D and C indicate deciduous and coniferous forest catchment, respectively), September 11-13 (E040911-D and -C), and September 16-18 (E040916-D and -C). We found a negative relationship between discharge intensity and EC in streamwater. The E040911 and E040916 showed slack change of stream discharge in comparison to E040907 due to contribution of base flow recharged by much precipitation. Moreover, NO/sub 3//sup -/ concentrations in E040911-C were highest, which may have resulted from forest management such as thinning in 2004. The relationship between pH and alkalinity in stream water showed that much of stream water have been recharged through subsurface. We conclude that subsurface discharge highly influences streamwater quality in a forested catchment, and the seperation of stream water discharge is therefore necessary to sustainable water management.