• Journal of Korea Water Resources Association
• /
• v.42 no.2
• /
• pp.149-160
• /
• 2009

The objective of this study is to suggest parameter regionalization scheme which is integrated two multivariate statistical methods: principal components analysis(PCA) and hierarchical cluster analysis(HCA). This technique is to apply semi-distributed rainfall-runoff model on ungauged catchments. 7 catchment characteristics (area, mean altitude, mean slope, ratio of forest, water content at saturation, field capacity and wilting point) are estimated for 109 mid-sized sub-basins. The first two components from PCA results account for 82.11% of the total variance in the dataset. Component 1 is related to the location of the catchments relevant to the altitude and Component 2 is connected with the area of these. 103 ungauged catchments are clustered using HCA as the following 6 groups: Goesan 23, Andong 6, Imha 5, Hapcheon 21, Yongdam 4, Seomjin 44. SWAT model is used to simulate runoff and the parameters of the model on the 6 gauged basins are estimated. The model parameters were regionalized for Soyang, Chungju and Daecheong dam basins which are assumed as ungauged ones. The model efficiency coefficients of the simulated inflows for these three dams were at least 0.8. These results also mean that goodness of fit is high to the observed inflows. This research will contribute to estimate and analyze hydrologic components on the ungauged catchments.

• Journal of Korea Water Resources Association
• /
• v.46 no.8
• /
• pp.833-842
• /
• 2013

The quantile mapping is utilized to reproduce reliable GCM(Global Climate Model) data by correct systematic biases included in the original data set. This scheme, in general, projects the Cumulative Distribution Function (CDF) of the underlying data set into the target CDF assuming that parameters of target distribution function is stationary. Therefore, the application of stationary quantile mapping for nonstationary long-term time series data of future precipitation scenario computed by GCM can show biased projection. In this research the Nonstationary Quantile Mapping (NSQM) scheme was suggested for bias correction of nonstationary long-term time series data. The proposed scheme uses the statistical parameters with nonstationary long-term trends. The Gamma distribution was assumed for the object and target probability distribution. As the climate change scenario, the 20C3M(baseline scenario) and SRES A2 scenario (projection scenario) of CGCM3.1/T63 model from CCCma (Canadian Centre for Climate modeling and analysis) were utilized. The precipitation data were collected from 10 rain gauge stations in the Han-river basin. In order to consider seasonal characteristics, the study was performed separately for the flood (June~October) and nonflood (November~May) seasons. The periods for baseline and projection scenario were set as 1973~2000 and 2011~2100, respectively. This study evaluated the performance of NSQM by experimenting various ways of setting parameters of target distribution. The projection scenarios were shown for 3 different periods of FF scenario (Foreseeable Future Scenario, 2011~2040 yr), MF scenario (Mid-term Future Scenario, 2041~2070 yr), LF scenario (Long-term Future Scenario, 2071~2100 yr). The trend test for the annual precipitation projection using NSQM shows 330.1 mm (25.2%), 564.5 mm (43.1%), and 634.3 mm (48.5%) increase for FF, MF, and LF scenarios, respectively. The application of stationary scheme shows overestimated projection for FF scenario and underestimated projection for LF scenario. This problem could be improved by applying nonstationary quantile mapping.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.14 no.1
• /
• pp.1-10
• /
• 2011

To understand characteristics of the water quality on the coastal boundary on tidal flat, field observations between 2008 and 2009 were undertaken twice a month at five coastal areas (Muan bay, Tando bay, Hampyeong bay, Shinan Jido and Yeongkwang coastal areas). Yearly water temperature difference was large with the range between $1.3^{\circ}C$ and $31.1^{\circ}C$. Salinity was about 32 but was the lower less than 20 for the heavy rainfall season. DO was high in winter and low in summer according to the variation of water temperature. pH represented the variation similar to DO. Suspended solid was averagely high over 100 mg/l in Yeongkwang coastal area, especially. COD did not revealed large variation with the value of about 1 mg/l. DIN and DIP concentration were high when freshwater was highly input in summer. DIN concentration was low for winter and early spring but DIP concentration did not show the seasonal variation with the continuous increase from July 2009 to December 2009. Chlorophyll a appeared high for spring with approximately $10\;{\mu}g/l$ and was higher for summer in Yeongkwang coastal area than other sites. The results of principal component analysis conducted to compare the characteristics of water quality observed in study areas showed the distinguishable features as follows. The freshwater input fluctuation appeared as the first factor in Muan and Tando bays, and the change of water temperature was the first factor in Shinan Jido and Yeongkwang coastal areas. The influence mixed with the variation of freshwater outflow and the change of water temperature in Hampyeong bay was to be the first factor.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.6 no.1
• /
• pp.119-131
• /
• 2003

Rainfall-runoff process is under the control of hydrologic parameters having temporal and spatial variety. Accordingly, it is difficult to efficiently deal them since many parameters and various information are required to perform hydrologic simulation. So the purposes of this study is to estimate the runoff volume by frequency using GIS techniques and NRCS method. The analysis of frequency rainfall is analyzed using FARD 2002 program and the result of goodness of fit test show that Log-pearson type III is suitable distribute type for the applied area. TOPAZ program used for the analysis of DEM data examining into geological characteristic. NRCS curve numbers estimated using landuse map and soil map for the estimation of effective rain fall in the basin. The storm Type II and Type III were used as the type for the application of NRCS. The result of application show that the runoff volumes above 80 years frequency in return period have similar patterns regardless of Type II and Type III. In addition, the results of comparison with runoff volumes by frequency in the report of river improvement master plan show that it have similar volumes as the relative errors for them of 80, 100 years frequency are each 7.65%, 5.33%.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.519-519
• /
• 2015

2007년 발간된 IPCC의 4차 평가보고서에서 자연재해, 환경, 해양, 농업, 생태계, 보건 등 다양한 부분에 미치는 기후변화의 영향에 대한 과학적 근거들이 제시되면서 기후변화는 현세기 범지구적인 화두로 대두되고 있다. 또한, 기후변화에 의한 지구 온난화는 대규모의 수문순환 과정에서의 변화들과 연관되어 담수자원은 기후변화에 대단히 취약하며 미래로 갈수록 악영향을 받을 것으로 6차 기술보고서에서 제시하고 있다. 특히 우리나라는 지구온난화가 전 지구적인 평균보다 급속하게 진행될 가능성이 높기 때문에 기후변화에 대한 담수자원 취약성이 더욱 클 것으로 예상된다. 따라서 지표수에 용수의존도가 높은 우리나라의 댐 저수지를 대상으로 기후변화에 따른 수환경 변화의 정확한 분석과 취약성 평가는 필수적이다. 본 연구에서는 SRES A1B 시나리오를 적용하여 기후변화가 주암호 저수지의 수환경 변화에 미치는 영향을 분석하였다. 지역스케일의 미래 기후시나리오 생산을 위해 인공신경망(Artificial Neural Network.,ANN)기법을 적용하여 예측인자(강우, 상대습도, 최고온도, 최저온도)에 대해 강우-유출모형에 적용이 가능한 지역스케일로 통계적 상세화를 수행하였으며, 이를 유역모델에 적용하여 저수지 유입부의 유출량 및 부하량을 예측하였다. 유역 모델의 결과를 토대로 저수지 운영모델에 저수지 유입부의 유출량을 적용하여 미래 기간의 방류량을 산정하였으며, 최종적으로 저수지 모델에 유입량, 유입부하량 및 방류량을 적용하여 저수지 내 오염 및 영양물질 순환 및 분포 예측을 통해서 기후변화가 저수지 수환경에 미치는 영향을 평가하였다. 기후변화 시나리오에 따른 상세기 후전망을 위해서 기후인자의 미래분석 기간은 (I)단계 구간(2011~2040년), (II)단계 구간(2041~2070년), (III) 단계 구간(2071~2100년)의 3개 구간으로 설정하여 수행하였으며, Baseline인 1991~2010년까지의 실측값과 모의 값을 비교하여 검증하였다. 강우량의 경우 Baseline 대비 미래로 갈수록 증가하는 것으로 전망되었으며, 2011년 대비 2100년에서 연강수량 6.4% 증가한 반면, 일최대강수량이 7.0% 증가하는 것으로 나타나 미래로 갈수록 집중호우의 발생가능성이 커질 것으로 예측되었다. 유역의 수문 수질변화 전망도 강수량 증가의 영향으로 주암댐으로 유입하는 총 유량이 Baseline 대비 증가 하였으며, 유사량 및 오염부하량도 증가하는 것으로 나타났다. 저수지 수환경 변화 예측결과 유입량이 증가함에 따라서 연평균 체류시간이 감소하였으며, 기온 및 유입수온 상승의 영향으로 (I)단계 구간대비 미래로 갈수록 상층 및 심층의 수온이 상승하는 것으로 나타났다. 연중 수온성층기간 역시 증가하는 것으로 나타났으며, 남조류는 (I)단계 구간 대비 (III)단계 구간으로 갈수록 출현시기가 빨라지며 농도 역시 증가하였다. 또한 풍수년, 평수년에 비해 갈수년에 남조류의 연평균농도 상승폭과 최고농도가 크게 나타나 미래로 갈수록 댐 유입량이 적은 해에 남조류로 인한 피해 발생 가능성이 높아질 것으로 예상된다.

• Journal of Soil and Groundwater Environment
• /
• v.13 no.1
• /
• pp.77-91
• /
• 2008

In this study, we developed a technique of applying DRASTIC, which is the most widely used tool for estimation of groundwater vulnerability to the aqueous phase contaminant infiltrated from the surface, and a groundwater flow model jointly to assess groundwater contamination potential. The developed technique is then applied to Buyeo-eup area in Buyeo-gun, Chungcheongnam-do, Korea. The input thematic data of a depth to water required in DRASTIC model is known to be the most sensitive to the output while only a few observations at a few time schedules are generally available. To overcome this practical shortcoming, both steady-state and transient groundwater level distributions are simulated using a finite difference numerical model, MODFLOW. In the application for the assessment of groundwater vulnerability, it is found that the vulnerability results from the numerical simulation of a groundwater level is much more practical compared to cokriging methods. Those advantages are, first, the results from the simulation enable a practitioner to see the temporally comprehensive vulnerabilities. The second merit of the technique is that the method considers wide variety of engaging data such as field-observed hydrogeologic parameters as well as geographic relief. The depth to water generated through geostatistical methods in the conventional method is unable to incorporate temporally variable data, that is, the seasonal variation of a recharge rate. As a result, we found that the vulnerability out of both the geostatistical method and the steady-state groundwater flow simulation are in similar patterns. By applying the transient simulation results to DRASTIC model, we also found that the vulnerability shows sharp seasonal variation due to the change of groundwater recharge. The change of the vulnerability is found to be most peculiar during summer with the highest recharge rate and winter with the lowest. Our research indicates that numerical modeling can be a useful tool for temporal as well as spatial interpolation of the depth to water when the number of the observed data is inadequate for the vulnerability assessments through the conventional techniques.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.3
• /
• pp.265-271
• /
• 2020

Automotive radar that is one of the most important equipment in high-tech vehicles, is commonly used to detect the speed and range of objects such as cars. In this paper, in addition to objects detection, a method of retrieving precipitation information using the automotive radar data is proposed. The proposed method is based on the fact that the degree of attenuation of the returned radar signal differs depending on the precipitation intensity and the assumption that the distribution of precipitation is constant in short spatial and temporal observation. The purpose of this paper is to assesses the possibility of retrieving precipitation information using a vehicle radar. To verify the feasibility of the proposed method during actual driving, a method of estimating precipitation information for each time segment of various precipitation events was applied. From the results of driving field experiments, it was found that the proposed method is suitable for estimating precipitation information in various rainfall types.

• Proceedings of the KAIS Fall Conference
• /
• 2011.05a
• /
• pp.151-154
• /
• 2011

$NO_x$ 제어 기술로는 크게 연소 전 탈질, 연소 개선 및 연소 후 탈질 기술로 구분할 수 있으며, 연소 후 탈질 기술에 속하는 SCR은 촉매를 사용하여 $NO_x$를 환원하는 대표적인 배연탈질기술이다. SCR의 $NO_x$ 저감 성능은 촉매 요인(촉매 구성물질, 형태, 공간속도 등)과 배가스의 온도, 유속 분포, 공정 운전 조건 등의 다양한 인자에 의해 좌우되는데 특히, 촉매층으로 유입되는 유동의 균일도는 가장 중요한 요소가 된다. 유동이 균일하지 않을 경우 촉매 전단에 편류가 발생하게 될 것이며 일정 촉매만 사용하게 되어 촉매 사용주기 감소 및 SCR 성능 저하를 초래할 수 있기 때문이다. 본 연구에서는 3차원 수치 해석 기법을 이용하여 설계 초기의 SCR 반응기 내 유동 특성을 모사하여 기류 균일도 여부를 확인하고, SCR 내 유동 균일도를 최적화시키기 위한 설계를 목적으로 설치하는 가이드 베인과 배플, 다공판이 반응기 내부 유동 및 촉매층의 기류 균일도에 미치는 영향에 대하여 연구를 수행하였다. 그 결과, 유동 개선을 위해 인입 덕트 곡관부에 가이드 베인을 설치하여 처리가스를 적절하게 배분시키고, 반응기 상단에 3단 배플을 설치한 결과 반응기 내부 유동의 편류 개선에 매우 효과적임을 알 수 있었다. 또한 다공판을 예비 촉매층 하단부 위치에 추가로 설치함에 따라 유동을 한번 더 완충시킬 수 있어 기류 균일도가 매우 양호해짐을 알 수 있었다.

• Economic and Environmental Geology
• /
• v.46 no.6
• /
• pp.545-559
• /
• 2013

Until now, research achievements of groundwater such as groundwater to depth distribution, usage, the available amount of development, water quality have been written in the watershed units($25{\sim}250km^2$). However, complex topography and geology, and the rivers of our country does not fit. And a clear management standards have not been able to present measures in groundwater quantity, water quality management such as rainfall, groundwater, utilization, water quality, pollution, etc. Therefore, in this study, the classification criterion of subwatershed unit($2.5{\sim}25km^2$), which is suitable for topography and geology of Korea, for rainfall-rating, groundwater level-rating, groundwater pollution-rating, groundwater quality-rating presented and proved its efficiency by applying in Hampyeong-Gun area.

• Journal of Korea Water Resources Association
• /
• v.44 no.5
• /
• pp.351-362
• /
• 2011

The soil moisture measurements and correlation analysis are presented to improve understanding the hydrological process at the hillslope scale. The rainfall events is a main driver of soil moisture variation, and its stochastic characteristic need to be properly treated prior to the correlation analysis between soil moisture measurements. Using field measurements for two designated periods during the late summer and autumn seasons in 2007 obtained from the Bumrunsa hillslope located at the Sulmachun watershed, prewhitened correlation analysis were performed for 8, 14, 7 and 7 relationships representing the vertical, lateral, recharge and return flows, for two designated periods, respectively. The analysis indicated both temporal and spatial variation patterns of hydrological processes, which can be explained by the relative contribution of matrix and macropore flows and the impact of transect topography, respectively.