• Journal of Korean Society on Water Environment
• /
• v.22 no.5
• /
• pp.856-864
• /
• 2006

For estimating the minimum discharge to maintain a river, low flow analysis is required and long term runoff records are needed for the analysis. However, runoff data should be estimated to run a hydrologic model for ungaged river basin. For the reason, parameter estimation is crucial to simulate rainfall-runoff events for those basins using Tank model. In this study, only runoff data recorded for dry season are used for parameter estimation, which is different to other methods based on runoff data recorded for wet and dry seasons. The Harmony Search algorithm is used to determine the optimum parameters for Tank model. The coefficient of determination ($R^2$) is served as the objective function in the Harmony Search. In cases that recorded data are insufficient, the recording interval is changed and Empirical CDF is adopted to analyze the estimated parameters. The suggested method is applied to Yongdam dam, Soyanggang dam, Chungju dam and Seomjingang dam basins. As results, the higher $R^2s$ are obtained when the shorter recording interval, the better recorded data quality, and the more rainfall events recorded along with certain rainfall amount is. Moreover, when the total rainfall is higher than the certain amount, $R^2$ is high. Considering the facts found from this study for the low flow analysis, it is possible to estimate the parameters for Tank model properly with the desired confidence level.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.6
• /
• pp.143-151
• /
• 2009

Extreme hydrologic events cause serious disaster, such as flood and drought. Many researchers have an effort to estimate design rainfalls or discharges. This study evaluated parameter estimation methods to estimate probability rainfalls with low uncertainty which will be used in design rainfalls. This study collected rainfall data from Incheon, Gangnueng, Gwangju, Busan, and Chupungryong gage station, and generated synthetic rainfall data using ARMA model. This study employed the maximum likelihood method and the Bayesian inference method for estimating parameters of the Gumbel and GEV distribution. Using a bootstrap resampling method, this study estimated the confidence intervals of estimated probability rainfalls. Based on the comparison of the confidence intervals, this study recommended a proper parameter estimation method for estimating probability rainfalls which have a low uncertainty.

• Korean Journal of Hydrosciences
• /
• v.6
• /
• pp.81-98
• /
• 1995

A linear reservoir rainfall-runoff system was developed as a rainfall-runoff event simulation model. It was achieved from large modification of runoff function method. There are six parameters in the model. Hydrologic losses consist of some quantity of initial loss and some ratio of rainfall intensity followed by initial loss. The model has analytical routing equations. Hooke and Jaeves algorithm was used for model calibration. Parameters were estimated for flood events from '84 to '89 at Seomyeon and Munmak stream gauges, and the trends of major parameters were analyzed. Using the trends, verifications were performed for the flood event in September 1990. Because antecedent rainfalls affect initial loss, future researches are required on such effects. The estimation method of major parameters should also be studied for real-time forecasting.

• Proceedings of the Korea Contents Association Conference
• /
• 2014.06a
• /
• pp.83-84
• /
• 2014

For hydrologic applications, lake levels is very important. As a first step in developing a remote-sensing based approach, lake stage estimation using remote sensing was proposed with the SRTM data from February 2000, which was providing a one-time snapshot. After several steps using contouring, masking, and CED, it was found that iterative contour fitting to a lake outline provided the outstanding result with the operator's decision. If the lake size is large enough, a constant meter of the difference removal due to bias found by Bhang et al. (2007) might be useful for more accurate estimations for the methods. A lake-level snapshot using SRTM data could provide estimates within 0.5 m level of accuracy for large lakes (> $10km^2$) with contouring. Also, even if the processing algorithm is complex, the accuracy was reliable. Overall, we confirmed that this study would provide useful information to ameliorate the quality of the SAR-derived DEMs specifically for water areas and if more expanded, SAR images can fruit result in water monitoring.

• Water for future
• /
• v.28 no.1
• /
• pp.133-144
• /
• 1995

The subject of the paper is the selection of the number and location of rainguage stations among existing ones, which will be part of real-time data collection system, for the computation of mean areal precipitation and for use as input of real-time flow forecasting models. The weighted average method developed by National Weather Service was used to compute MAP. Two different searching methods were used to find local optimal solutions as a function of the number of rainguages. An operational rainfall-runoff model was used to determine the optimal location and number of stations for flow prediction.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.583-587
• /
• 2005

At present, various methods are available to analyze storm runoff data. Among these, application of Z-transform is comparatively simple and new, and the technique can be used to identify rainfall and unit hydrograph from analysis of a single storm runoff. The technique has been developed under the premise that the rainfall-runoff process behaves as a linear system for which the Z-transform of the direct runoff equals the product of the Z-transforms of the transfer function and the rainfall. In the hydrologic literatures, application aspects of this method to the rainfall-runoff process are lacking and some of the results are questionable. Thus, the present study provides the estimation of Z-transform technique by analyzing the application process and the results using hourly runoff data observed at the research basin of International Hydrological Program (IHP), the Pyeongchanggang River basin. This study also provides the backgrounds for the problems that can be included in the application processes of the Z-transform technique.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.535-539
• /
• 2009

Evapotranspiration (ET) is one of the main factor to understand the hydrologic cycle on land surfaces of entire globe. It accounts for about 65% of precipitation returning to the atmosphere. Accurate estimation of the ET is essential to many applications of water resources management, hydrology, meteorology, climatology, and agriculture. Over the past few decades, there have been extensive efforts to develop and validate a number of ET models. Priestley-Taylor (P-T) and Food and Agriculture Organization Penman-Monteith (P-M) models are generally recognized as simple, but great operational approaches to estimate ET over different land cover types. In this study, we compare/validate different models of increasing complexity, P-T, P-M, and Common Land Model (CLM) in croplands, IA.

• Water for future
• /
• v.12 no.1
• /
• pp.21-27
• /
• 1979

Ground water stored in the alluvium and the rocks provides the vase flow of the streams and can be withdraw from wells and infiltration galleries. And it is also recharge naturallyby precipitation. The amount of ground water in the four major basins it is estimated to be about 137,000 million cubiv meters(Table1), while nationwide ground water storage to be about 232,000 million cubic meters. The estimation of storage volume has been made on the basis of assumed thickness of the saturated zone of the different rocks and assumed porosities of those rocks. The values of the porosity of alluvium and saprolite were assumed to be 25% and 40% respectivvely which are based on tests made of similar materials in Georgia, U.S. The volume of water in storage is believed to be a conservative estimate. Detailed geologic and hydrologic investigation should be made where and when water resources are needed.

• Journal of Korean Society of Rural Planning
• /
• v.9 no.4 s.21
• /
• pp.1-7
• /
• 2003

This study was conducted to seek the effective water management method of the irrigation reservoirs. Joongpyong reservoir was selected for the hydrologic monitoring, and investigated from May in 1999 to December in 2001. The water level and amount of outlet discharge were measured, the stage discharge equation as a rating curve was induced, and which were compared to the irrigation water requirements calculated by a daily simulation model. The water balance of Joongpyong reservoir was analyzed, mainly on the reservoir storage ratio during irrigation period. Comparing the observed storage and simulation data, the results of the simulation were well agreed with the measured data.

• Current Research on Agriculture and Life Sciences
• /
• v.29
• /
• pp.29-35
• /
• 2011

The relationship between hydrologic processes and scale is one of the more complex issues in surface water hydrology. Disturbances that change vegetation and/or soil properties have been known to subsequently alter the landscape. The primary objective of this study was to estimate the grain size of soils with different properties from the hydraulic conductivity using pedotransfer functions. The double ring infiltrometer method was used to measure the vertical hydraulic conductivity of three soils under different soil planar surface treatments. Seven selected pedotransfer functions were used to estimate percentile diameters and the reduction in infiltration caused by compaction was misconstrued as caused by changes in percentile diameter. Results showed that compaction on the sandy loamy foot paths reduced the hydraulic conductivity by about 50%. The study showed that perceptual models of infiltration processes and appreciation of scale problems in modeling are far more sophisticated than normally presented in texts. Hydraulic measurement methods are still relevant and will provide significant information of grain size of the soils.