• Journal of Soil and Groundwater Environment
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• v.23 no.6
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• pp.37-45
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• 2018

The source of Chusan Spring water in the Ulleungdo is the precipitation in the Nari caldera basin, which permeates in the Trachitic pumice and tuff area and moves downward, outflowing at the lithologic boundary between the trachyte and Nari tuff. It is known that the discharge rate of the Chusan Spring is large enough to be used for the small hydroelectric power generation, but the exact discharge rate and hydrogeologic characteristics have not been known. The discharge rates of the Spring were measured 11 times, which ranged from $15,220m^3/d$ to $36,278m^3/d$. The discharge rates, measured by the automatic level recorder, for two-year period, were $20,000{\sim}38,000m^3/d$. The variation of discharge rates did not coincide with rainfall event, but showed daily increases of $3,000{\sim}5,000m^3/d$. The annual discharge rate excluding the evapotranspiration and the surrounding stream discharge corresponded to 70.6% of the annual precipitation of the recharge area. Therefore, meteorological observations at the Nari basin, rather than the Ulleung-do meteorological station, are more appropriate to properly interpret the discharge characteristics of the Chusam Spring and the recharge rate of the basin.

• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.405-420
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• 2007

This study is intended to analyze and evaluate the effects of Seomjingang Dam and Soyanggang Dam Catchment on water circulation in order to examine water balance change of watershed by climate change. Obviously, air temperature and precipitation showed a gradually increasing trend for the past 30 years; evapotranspiration vary in areas and increasing annual average air temperature is not always proportional to increasing evapotranspiration. Based on Penman-FAO24, climatic water balance methods and measured values are shown to be significantly related with each other and to be available in Korea. It is certainly recognized that increasing annual rainfall volume leads to increasing annual runoff depth; for fluctuation in annual runoff rates, there are some difference in changes in measured values and calculated values. It is presumably early to determine that climate changes has a significant effect on runoff characteristic at dam catchment. It is widely known that climate changes are expected to cause many difficulties in water resources and disaster management. To take appropriate measures, deeper understanding is necessary for climatological conditions and variability of hydrology and to have more careful prospection and to accumulate highly reliable knowledge would be prerequisites for hydrometric network.

• Journal of Korea Water Resources Association
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• v.37 no.2
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• pp.133-144
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• 2004

A Tank Model composed of 4 tanks with soil moisture structure was applied to Daecheong Dam and Soyanggang Dam watersheds. Calibration and verification were repeated 332 and 472 times for each watershed using SCE-UA global optimization method for different calibration periods and objective functions. Four different methods of evapotranspiration calculation were used and evaluated. They are pan evaporation, 1963 Penman, FAO-24 Penman-Monteith, and FAO-56 Penman-Monteith methods. Tank model with soil moisture structure showed better results than the standard tank model for daily rainfall-runoff simulation. Two types of objective function for model calibration were found. Proper calibration period are 3 years, in which dry year and flood year are included. If a calibrationperiod has an inadequate runoff rate, the period should be more than 8 years. The four methods of eyapotranspiraton computation showed similar results, but 1963 Penman method was slightly inferior to the other methods.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.260-269
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• 1986

This experiment was conducted to investigate the effect of mulching materials on the emergence rate, root dry weight and grain weight of sesame using variety Poong Nyun Ggae and also their effects on physical properties of soil, evapotranspiration and weed growth on the respective plots were studied. The effect of soil water holding capacity at mulching with polyethylene film and straw increased 5.4%, 2.8% to non-mulched plot respectively. The maximum soil temperature was raised up to 4$^{\circ}C$ by applying clear film and was dropped down to 7$^{\circ}C$ by straw. The minimum soil temperature was raised up to 2$^{\circ}C$ by clear film and was dropped down to 3$^{\circ}C$ by straw. In the early stage, the soil physical properties of clear film mulching were better than those of non mulching, and so was in emergence rate. In the late stage, soil strength was high at non mulching, and soil porosity, soil aeration and water infiltration rate were high at film and straw mulchings. Total root dry weight was great at clear film mulching, and root dry weight was concentrated mainly in the upper 10 cm of soil profile. The amount of weeds collected was the least at black film mulching. There were of little difference in evapotranspiration among treatments. The grain yield of sesame was increased to 57% by polyethylene film and 25% by straw mulching.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.351-356
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• 2002

Groundwater recharge rate was estimated by applying the groundwater level fluctuation method utilizing Theis (1937) approach with specific yield estimation technique of Shevenell (1996) and the temperature method using observed data from National Groundwater Observation Stations. Results based on analysis of water level observation data of 10 alluvium wells reveal that the recharge rates for 5 wells of Kum river area range 3.7~25.0% and those for 5 wells of Nakdong river area range 3.6~21.7%. Results obtained from the temperature method based on water temperature data indicated that the upward flow resulted from evapotranspiration is dominant for 4 wells of the Kum river area and 5 wells of the Nakdong river area. The other wells showed the downward flow which is related to groundwater recharge in these areas.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.95-104
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• 1988

This study refers to the development of a hydrologic model simulating daily inflow and release rates for inigation reservoirs. A daily - based model is needed for adequate operation of an irrigation reservoir sufficing the water demand for paddy fields which is closely related to meteorological conditions. And the objective of this study is to develop a reservoir release rate model and then to calibrata the parameters. The release rates model considers daily water demands , water supply for transplanting, minmum release for maintaining canal flow, and maxirnun and regular flooding depth for determining effective rainfall on paddy fields. Each of the factors in the model was regarded as a lumped pararuter representing the average condition of a whole irrigated area. The water demand was estimated form the potential evapotranspiration by Penman method, the effective rainfall, and the infiltration on paddy fields. The release model was found to be capable of adequately simulating daily reservoir releases based on meteorological data.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.431-434
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• 2003

This research developed a method for the estimation of groundwater recharge by yielding daily soil moisture content and watershed evapotranspiration from the water balance concept of the unsaturated and saturated layers in rainfall-runoff model called DAWAST. The goal of the research is to estimate the groundwater recharge fulfilling conditions of the safe discharge for any season. To meet this goal, the data of groundwater level and stream flow rate have been monitored in a study area and used to validate the model.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.523-531
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• 2013

In this study, a method of simulating ephemeral stream runoff characteristics in Jeju watershed is newly suggested. The process based conceptual-physical scheme is established based on the SWAT-K and applied to Cheonmi-cheon watershed which shows the typical pattern of ephemeral stream runoff characteristics. For the proper simulation of this runoff, the intermediate flow and baseflow are controlled to make downward percolation should be dominant. The result showed that surface runoff simulated by using the modified scheme showed good agreement with observed runoff data. In addition, it was found that the estimated runoff directly affected the groundwater recharge rate. This conceptual model should be continuously progressed including rainfall interception, spatially estimated evapotranspiration and so forth for the reasonable simulation of the hydrologic characteristics in Jeju island.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.601-613
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• 2011

This study is focused on a climate data integrity to improve water quality assessment due to the social development projects. The study is in an attempt to calculate both extreme ranges of weather data measurements and partly provide means to assess qualification of data which fall within the extremes at the 23 meteorological weather stations. Generally speaking, maximum temperature, minimum temperature, relative humidity, dew point temperature are in the range of reasonable accuracy. However, there found some outliers of the brightness sunshine hours in Cheonan station. Also some years in Gwangju, Seoul, Wonju, Busan, and Jeju never reach to their upper limit and perhaps the calibration of the equipment is doubtful. The users need to take cautions in using the brightness sunshine hour data in preparation of water resources planning and management by estimating evapotranspiration and river discharge, and/or growth rate of the algae (phytoplankton).

• Journal of Environmental Science International
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• v.30 no.8
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• pp.613-619
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• 2021

Soil water enters the atmosphere via evapotranspiration, where it transforms into atmospheric water vapor and plays important role in the surface-atmosphere energy exchange. Soil conditions have a direct influence on the effective rainfall, and initial soil moisture conditions are important for quantitatively evaluating the effective rainfall in a watershed. To examine the sensitivity of the initial saturation to hydrologic outflow, a two-dimensional distributed FLO-2D hydrologic model was applied to a small watershed. The initial saturation was set to 0.3, 0.5, and 0.7 and the obtained results were compared. The Green-ampt model was chosen to calculate the penetration loss. Depending on the initial soil moisture, the peak flow rate varied by up to 60%, and the total water volume in the watershed by approximately 40%.