• Journal of Korea Water Resources Association
• /
• v.34 no.5
• /
• pp.511-519
• /
• 2001

Global warming has begun since the industrial revolution and it is getting worse recently. Even though the increase of greenhouse gases such as $CO_2$is thought to be the main cause for glogal warming, its impact on global climate has not been revealed clearly in rather quantitative manners. The objective of this research is to predict the hydrological environment changes in the Daechung Dam basin due to the global warming. A mesoscale atmospheric/hydrologic model (IRSHAM96 model) is used to predict the possible changes in precipitation and temperature in the Daechun Dam basin. The simulation results of IRSHAM96 model and a conceptual water balance model are used to analyze the changes in soil moisture, evapotranspiration and runoff in the Daechung Dam basin. From the simulation results using the water balance model for 1x$CO_2$and 2x$CO_2$situations, it has been found that the runoff would be decreased in dry season, but increased in wet season due to the global warming. Therefore, it is predicted that the frequency of drought and flood occurrences in the Daechung Dam basin would be increased in 2x$CO_2$condition.

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

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.6
• /
• pp.579-582
• /
• 2012

Removing residual water in a fuel cell is a critical operational process for managing its performance and controlling its lifetime. Understanding the mechanism of water transport in fuel cells is essential for the design of the water removal process. In this study, an experimental method for measuring the water evaporation rate through a gas diffusion layer, which is a porous medium, under steady-state conditions was developed. Experimental bench tests were conducted to apply the developed method. Then, the effects of various parameters of the drying gas and the gas diffusion layer were experimentally measured. The water evaporation rate increased as the humidity of the drying gas decreased and the flow rate of the drying gas increased. In addition, a thinner gas diffusion layer yielded a higher water evaporation rate.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1614-1618
• /
• 2007

분포형 수문모형은 유역을 격자단위로 세분화하여 매개변수를 부여하고, 증발산, 침투, 지표면유출, 중간유출, 지하수유출, 하도흐름 등 여러 가지 수문요소를 해석하는 종합적인 수문모형이다. 지표면에 내린 강우의 증발 및 침투, 유출은 토양수분의 함량에 크게 의존하게 된다. 따라서 토양수분에 대한 적절한 모의가 분포형 수문모형의 정확도를 좌우하는 핵심이라 할 수 있다. 토양수분은 식물의 생장 및 가용수자원 산정 등에 있어서 중요한 요소로서 토양층 상부의 수 미터 내에 존재하는 수분의 양을 일컫는다. 토양수분의 공간적 시간적 특성들은 증발, 침투, 지하수 재충전, 토양침식, 식생분포 등을 지배하는 매우 중요한 요소라 할 수 있다. 강우로 인한 지면과 지표하에서의 순간적인 포화공간의 형성 및 유출의 생성을 포함하는 과정과 증발산 등은 모두 비포화대(vadose zone) 혹은 토양층에서의 토양수분의 함량에 크게 의존하게 된다(이가영 등, 2005) 본 연구에서는 토양수분에 대한 정밀측정 자료가 있는 설마천 유역 범륜사 사면에 대하여 분포형 수문모형의 토양수분 해석 능력을 평가하고자 하였다. 토양수분 모의에 사용된 격자기반의 분포형 수문모형은 미공병단에서 개발한 GSSHA(USACE, 2006) 모형이다. 모형의 입력자료는 정밀토양도와 현장측정에 의한 토양매개변수를 반영하여 구축하였고, 강우 및 기상자료는 2003년 1월 1일 ${\sim}$ 2004년 12월 31일의 1시간 자료를 이용하였다. 모의기간 중 2003년은 초기 토양수분값 등 초기조건의 영향을 줄이기 위한 웜업 (Warm-up)기간으로 설정하였고, 2004년의 모의결과를 토양수분 관측값과 비교하였다.업지역, 상업지역 등과 같이 지형적 특성에 따른 유량측정망을 구축하는 것이다.의 의사결정 지원 도구가 될 것이다. 따라서, 본 연구에서는 도시유역의 물순환 해석을 위한 일련의 과정, 즉 자료의 조사 및 취득에서부터 물순환 해석 모형을 이용한 정량적 현황파악, 물순환 개선 기법 및 평가를 수행함에 있어 주요 착안점 및 실무에서의 기술적 가이드를 제공하고자 하였으며, 보다 세밀한 도시유역의 물순환 해석을 위하여 우리나라와 일본에서 적용이 활발한 물리적 기반의 분포형 모형(WEP, SHER, SWMM)의 적용사례를 통하여 국내 도시하천의 물순환 해석에 활용함에 있어서의 실질적인 적용절차 등을 제시하고자 하였다. 한다.호강유역의 급격한 수질개선을 알 수 있다.世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와 동년대에 동일한 목적으로 찬술되었음을 알 수 있다. $\ulcorner$경상도실록지리지$\lrcorner$(慶尙道實錄地理志)에는 $\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와의 비교를 해보면 상 중 하품의 통합 9개소가 삭제되어 있고, $\ulcorner$동국여지승람$\lrcorner$(東國與地勝覽) 에서는 자기소와 도기소의 위치가 완전히 삭제되어 있다. 이러한 현상은 첫째, 15세기 중엽 경제적 태평과 함께 백자의 수요 생산이 증가하자 군신의 변별(辨別)과 사치를 이유로 강력하게 규제하여 백자의 확대와 발전에

• Journal of Korea Water Resources Association
• /
• v.34 no.4
• /
• pp.335-345
• /
• 2001

The objective of this research is to analyze the hydrological environment changes in Daechung Dam Basin due to the global warming. GCM simulation results are used to predict the possible changes in precipitation and temperature. The changes of potential evapotranspiration, soil moisture and runoff due to the changes of precipitation and temperature are analyzed using a conceptual water balance model. From the simulation results using the water balance model for lx$CO_2$ and 2x$CO_2$ situations, it has been found that the runoff would decrease in Winter, but increase in Summer and Fall due to the global warming. Therefore, it is predicted that the frequency of drought and flood occurrences in Daechung Dam Basin would be increased in 2x$CO_2$ condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.309-312
• /
• 2007

The cryogenic fluid is the propellant for the liquid rocket engine. The design of space launcher vehicle is guided by minimum size and weight criteria, so the turbo pump solicits high impeller speed. Such high speed results in a zone of pressure drop below vapor pressure causing caivtation around inducer blades. The cryogenic fluid has different characters from isothermal fluid like water. The cryogenic fluid has very sensible thermodynamic properties and the phase change undergoes evaporative cooling. So, the developed code has to be modified cavitation modeling and it is added the energy equation for temperature sensitivity.

• Journal of Korea Water Resources Association
• /
• v.53 no.11
• /
• pp.939-949
• /
• 2020

Currently, the demand for farmland is steadily decreasing due to changes in the agricultural environment and dietary life. In line with this, the government adopted an integrated water management with the enactment of the Framework Act on Water Management on June 2019. Therefore, it is required to take a closer look at agricultural water demand that accounts for 61% of water use for efficient water resources management. In this study, the overal process was evaluated for estimating agricultural water demand. More specifically, agricultural water demand for paddy field, which comprises 67% to 87% of agricultural water demand, was reviewed in detail. The biggest issue in estimating the paddy field water demand is the selection of the method for potential evapotranspiration. FAO recommends Penman-Monteith, but, currently, our criteria suggest a modified Penman equation that shows over estimation. Also, the crop coefficient, which is the main factor in evaluating evapotranspiration, has an issue that does not consider the current climate and crop varieties because it was developed 23 years ago. Comparing the Modified Penman and Penman-Monteith equations using the data from Jeonju National Weather Service, the modified Penman equation showed a big difference compared to the Penman-Monteith equation. When the crop coefficient was applied, the difference between late May and late August increased, where the amount of evapotranspiration was high. The estimation process was applied to four study reservoirs in Gimje. Comparing the estimated water demand with the supplied water record from reservoirs, the results showed that the estimation accuracy depends on not just the potential evapotranspiration, but also the standard water storing level in paddy fields.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.58-58
• /
• 2021

물은 비, 눈의 형태로 지표면에 공급되며, 빗물이 땅속으로 침투, 저류되고 지표 및 지하흐름을 통해 강이나 바다로 유입되고 다시 증발산을 통해 순환 시스템을 이룬다. 또한, 물은 생명체의 생존에 필수적이며, 건강한 문순환 체계의 균형을 이루는 것이 안정적으로 물을 공급하는 것과 밀접한 관계가 있다. 최근 범지구적으로 기후변화 현상이 나타나고 있으며, 우리나라는 지난 50년간 도시화를 통해 수계와 임야를 제외한 전 국토에서 불투수면적이 22.4%를 차지한다(ME, 2016). 이와 같은 경향은 도시지역의 물순환 및 인프라에서 침수, 가뭄, 비점오염, 침투량 감소 등과 같은 수재해 문제의 우려가 있다. 이러한 문제를 해결하기 위해 물관리 일원화와 관련하여 다양한 정책들이 마련되고 있으며, 또한 도시개발 이전의 상태로 회복하기 위한 저영향개발 기술 및 도시지역의 현재 상태를 평가하기 위해 각 분야에 따른 지표 선정에 관한 다양한 연구가 진행되고 있다. 기존 연구사례에서는 대상 도시 내 물순환 체계 회복을 중점적으로 연구가 진행되었다. 물순환 체계는 수계별로 상·중·하류에 따라 인구밀도, 급경사에 따른 돌발홍수, 내수침수, 우수배제 등과 같은 문제가 도시별로 상이하게 발생하며, 추후 이와 관련된 연구가 필요하다. 본 연구에서는 우리 나라 수계에서 대표적인 한강, 낙동강, 금강, 영산강을 대상으로 각 도시에서는 입지특성에 따른 대응방법을 마련하기 위한 기초자료로써 4개의 수계로 구분하여 상·중·하류별로 위치한 도시지역의 물순환 및 인프라에 대해 분석하였다.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.698-703
• /
• 1998

The pervaporation experiments of aqueous solutions of trichloroethylene (TCE) and chlorobenzene (CB) through the silicone rubber (polydimethylsiloxane, PDMS) membrane were carried out and the effect of concentration polarization on the separation characteristics was investigated. The resistance-in-series model was used to explain the boundary layer resistance. It was clear that the concentration polarization phenomenon had a significant effect on the permeation behavior in the pervaporation separation of the trace organic chlorides from aqueous solutions. With the same membrane thickness, the permeation of TCE, which has a stronger affinity for the PDMS, appeared to be more influenced by the boundary layer resistance than that of CB. The effect of boundary layer resistance was reduced and the membrane resistance became dominant with increasing membrane thickness at a given hydrodynamic condition. The separation factor was increased to approach the intrinsic separation factor of the membrane with its thickness.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.43 no.4
• /
• pp.98-111
• /
• 2015

Urban environmental problems such as flooding, depletion of ground water, pollution of urban streams and the heat island effect caused by urban development and climate change can be mitigated by the improvement of the urban water cycle. For the effective planning of water cycle management it is necessary to establish aerial Hydrotope Maps, with which we can estimate the status and change of the water allowance for any site. The structure of the German water balance model BAGLUVA, which is based on soil and vegetation, was analyzed and the input data and boundary condition of the model was compared with Korean data and research results. The BAGLUVA Model consists of 5 Input categories (climate, land use, topography, soil hydrology and irrigation). The structure and interconnection of these categories are analyzed and new concepts and implementation methods of topographic factor, maximum evapotranspiration ratio, effective rooting depth and Bagrov n parameter was compared and analyzed. The relation of real evapotranspiration ($ET_a$)-maximum evapotranspiration ($ET_{max}$) - precipitation (P) was via Bagrov n factor represented. The aerial and land use oriented Hydrotope Map can help us to investigate the water balance of small catchment areas and to set goals for volume of rainwater management and LID facilities effectively in the city. Further, this map is a useful tool for implementing water resource management within landscape and urban planning.