• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1880-1884
• /
• 2007

The Natural Resource Conservation Service Curve Number(NRCS-CN) method is one of the widely used methods for computation of runoff from a basin. However, NRCS-CN method has weak point in that the spatial land use distribution characteristics are ignored by using area weighted CN value. This study developed a program which can estimate runoff by considering spatial distribution of CN and flow accumulation at the outlet of the watershed by appling Moglen's method. Comparisons between the results from NRCS-CN method and this study showed good agreement with measured data of experimental watersheds. The developed program predicted lower runoff than the conventional NRCS-CN method. As a conclusion, this study proposes a new design direction which can simulate real runoff phenomena. And the developed program could be applied into runoff minimization design for a basin development.

• Journal of Korean Society for Geospatial Information Science
• /
• v.12 no.1 s.28
• /
• pp.39-44
• /
• 2004

The SCS-CN method was known to have difficulties to the applied to the mountainous area like Korean river basins. This study focused to develop a distributed SCS-CN method considering river basin slopes from GIS data. For the purpose, the method was applied to Sulma river and compared with area weighted average method and distributed SCS-CN method using GIS. According to the results, SCS-CN method considering river basin slopes provided better effects on the estimating effective rainfall on the other methods. The necessity of the generalization of the results to the other rivers was discussed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.2
• /
• pp.493-503
• /
• 2014

The NRCS-CN method is generally applied for estimating effective rainfalls in practice, in which the basin-averaged CN is normally used. In order to develop a more appropriate method for estimating effective rainfalls in a basin, this study compared estimated effective rainfalls from two distinct methods with the observed direct runoff. The first method is to estimate the basin-representative effective rainfall using the basin-averaged CN (hereafter, effective rainfall I), whereas the second method to estimate the basin-averaged effective rainfall through areal-averaging sub-area effective rainfalls corresponding to the soil type and landuse type (hereafter, effective rainfall II). The overall results indicated that the effective rainfall II was higher than the effective rainfall I and closer to the observed direct runoff. The study also performed error analyses to verify that the effective rainfall II can be applied in practice in a basin as more accurate estimate of basin-representative effective rainfall.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.4
• /
• pp.1171-1180
• /
• 2014

The NRCS-CN method is generally used to estimate effective rainfalls in a basin. However, since the curve number which plays a critical role in the NRCS-CN method was originally developed for US watersheds, it is limited to be directly applied to other basins outside the United States. Therefore various modifications have been suggested to revise the NRCS-CN for specific watershed condition. This study introduced the weighted average method and the slope-based CN to estimate effective rainfalls available for Korean watersheds and compared with the observed direct runoff. The overall results achieved from this study indicated that the adjusted slope-based CN considerably increases effective rainfalls in general and makes the duration of effective storm longer. Based on the statistical error analysis performed for various modifications of NRCS-CN, the weighted average method with the adjusted slope-based CN has highest precision with the observed direct runoff. In addition, after analyzing the relation between the initial loss estimated from rainfall-runoff observations and the potential maximum retention from GIS-based data, it turns out that the assumption of linear relationship between the initial loss and the potential maximum retention is not available for Korean watersheds.

• Journal of Korean Society on Water Environment
• /
• v.26 no.4
• /
• pp.590-597
• /
• 2010

NRCS Curve Number (CN) method is widely used for practical purposes in the field by engineers and researchers to calculate direct runoff from total rainfall. However, CN is obtained from antecedent moisture condition and soil characteristics and so it has some problems due to its uncertainty. Therefore this study estimated CN of a watershed using asymptotic CN method which can estimate CN by rainfall and runoff data and compared the result with representative CN given by WAMIS. And we performed runoff simulation for rainy season of Bocheong stream by CN regression equation. From the result, we showed that it could be more reasonable to simulate direct runoff using watershed CN regression equation than WAMIS CN. Furthermore, we knew that the equation is more sensitive to small rainfall event.

• Natural Product Sciences
• /
• v.14 no.4
• /
• pp.254-259
• /
• 2008

An easy and reliable HPLC method was developed to determine allantoin in Dioscorea Rhizoma using cyano columns. Qualitative and quantitative analyses of allantoin were performed successfully by cyano columns (YMC-Pack CN column, Zorbax SB-CN column and Discovery$^{(R)}$ Cyano column). The intraday precision were 0.58 - 3.33% for YMC-Pack CN, 0.41 - 2.20 for Zorbax SB-CN and 0.45 - 1.93% Discovery$^{(R)}$ Cyano columns, while interday variations were 0.09 - 1.84%, 0.04 - 2.59% and 0.87 - 5.18% for YMC-Pack CN, Zorbax SB-CN and Discovery$^{(R)}$ Cyano columns. The recoveries of allantoin were in the range at 98.8 - 102.6% (RSD 1.1 - 1.6%) for YMC-Pack CN column, 99.7 - 110.5% (RSD 1.3 - 4.9%) for Zorbax SB-CN column, and 97.2 - 110.1% (RSD 1.8 - 5.7%) for Discovery$^{(R)}$ Cyano column. The contents of allantoin in four Dioscorea Rhizoma samples were determined by cyano columms and ranged at 4.1-7.1 mg/g dry weight. The present study indicated that HPLC method using cyano column for determining allantoin is a reliable method and this method can be applied to verify allantoin in Dioscorea Rhizoma.

• Journal of Radiation Protection and Research
• /
• v.21 no.3
• /
• pp.167-173
• /
• 1996

The calibration method for the detection efficiency of solid state track detector to alpha is presented, and the detection efficiency of CN-85 and LEXAN to alpha is measured by this method. The results are 97% and 57% in CN-85 and LEXAN, respectively. The reason for a better result in CN-85 in not only the high sensitivity but also the low energy dependency with comparing for LEXAN. The peak detection efficiency is 3MeV and 1.8MeV in CN-85 and LEXAN, respectively.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.215-215
• /
• 2017

NRCS-CN 방법은 총 강우량으로부터 유출량을 계산하는 방법으로, 국내에서는 설계홍수량 산정 시 NRCS-CN 방법의 사용을 권장하고 있다. CN값은 토지이용 및 피복, 토양특성, 수문학적 조건(AMC)에 따른 함수로 결정할 수 있으나, 보통의 경우 미국의 National Engineering Handbook (NEH-4)에서 제시한 표를 활용한다. 그러나, 우리나라의 토지피복 및 토지이용 현황은 미국과 다르기 때문에 현실 조건을 반영한 조정이 필요함에도 불구하고, 충분한 관측 자료가 확보되지 않아 이러한 조정이 어려운 실정이다. NRCS-CN 방법에서는 결과 값이 총 강수량보다 CN에 크게 의존적이기 때문에 부정확한 CN 값의 산정은 큰 오차를 야기할 수 있다. 또한 소유역에서는 초기손실량이 설계홍수량 산정에 큰 영향을 미치지만 우리나라는 초기손실률을 20%의 고정된 값을 일괄적으로 적용하고 있으며, 이는 제주도와 같은 특수한 투수성 지층에서는 적합하지 않다는 지적을 받아왔다. 여러 선행연구에서 강수량과 CN 사이에는 특정 관계식이 존재하며, 고정된 CN 값이 아닌 강수량에 따라 변화하는 값을 적용하는 것이 기존의 NRCS-CN 방법보다 더 정확한 결과를 나타낸다는 것이 확인된 바 있다. 본 연구에서는 NRCS-CN 방법의 CN 값과 초기손실률을 유역에 적합하게 개선하기 위해서 기존의 NRCS-CN 모형에 점근 유출곡선지수방법(Asymptotic CN Regression Method)을 통해 산정된 CN값과 각기 다른 초기손실률(0.01, 0.05, 0.10, 0.20, 0.40)을 적용하여 개선된 총 8개의 모형을 한강 권역 소유역에 적용하였다. RMSE, MAE 및 R-square 등의 지표를 이용하여 모형 검정을 수행하였으며, 최적의 모형 및 미개변수를 선정하였다. 그 결과 기존의 NRCS-CN 방법보다 점근 유출곡선지수방법을 적용했을 때 더 작은 오차를 나타내는 것을 확인하였으며, 대부분의 유역에서 0.01 또는 0.05 등 기존보다 더 작은 초기손실률을 채택 시 실측값과 가장 적은 오차를 나타냈다.

• Journal of Environmental Science International
• /
• v.15 no.3
• /
• pp.253-260
• /
• 2006

Groundwater recharge from precipitation is affected by the infiltration from ground surface and the movement of soil water. Groundwater recharge is directly related to the groundwater amount and flow in aquifers, and baseflow to rivers. Determining groundwater recharge rate for a given watershed is a prerequisite to estimate sustainable groundwater resources. The estimation of groundwater recharge rate were carried out for three subwatersheds in the Wicheon watershed and two subwatersheds in the Pyungchang River basin and for the period 1990-2000, using the NRCS-CN method and the baseflow separation method. The recharge rate estimates were compared to each other. The result of estimation by the NRCS-CN method shows the average annual recharge rate 15.4-17.0% in the Wicheon watershed and 26.4-26.8% in the Pyungchang River basin. The average annual recharge rates calculated by the baseflow separation method ranged 15.1-21.1% in the W icheon watershed, and 25.2-33.4% in the Pyungchang River basin. The average annual recharge rates calculated by the NRCS-CN method is less variable than the baseflow separation method. However, the average annual recharge rates obtained from the two methods are not very different, except NO. 6 subwatershed in Pyungchang River basin.

• Journal of Korea Water Resources Association
• /
• v.34 no.6
• /
• pp.735-743
• /
• 2001

CN procedure has been proven to be useful method for evaluating the effects of changes in land-use and treatment on hydrology. In this study, the use of Landsat multi-spectral image was investigated for analyzing the land-use distribution. From the Landsat data, forest areas were classified according to the density of trees. Watershed CN's were calculated to analyze the effects of the density of trees and soil cover types on direct runoff. According to the results, the density of trees had a little effect while soil cover types had a large effect on CN, From the comparison of estimated runoffs from CN method with observed runoffs, detailed soil cover map provides improved results.