• Journal of Korea Water Resources Association
• /
• v.30 no.4
• /
• pp.317-326
• /
• 1997

The Palmer Drought Severity Index has been ectensively used to quantitatively evaluate the drought severity at a location for both agricultural and water resources management purposes. In the present study the Palmer-type formula for drought index is drived for the whole country by analyzing the monthly rainfall and meteorological data at nine stations with a long period of records. The formula is then used to compute the monthly drought severity index at sixty-eight rainfall stations located throughout the country. For the past five significant drought periods the spatial variation of each drought is shown as a nationwide drought index map of a specified duration from which the relative severity of drought throughout the country is identifiable for a specific drought period. A comparative study is made to evaluate the relative severity of the significant droughts occurred in Korea since 1960's. It turned out that '94-'95 drought was one of the worst both in the areal extent and drought severity. It is found that the Palmer-type formula is a very useful tool in quantitatively evaluating the severity of drought over an area as well as at a point. When rainfall and meteorological forecast become feasible on a long-term basis the method could also be utilized as a tool for drought forecasting.

• Journal of Korea Water Resources Association
• /
• v.48 no.10
• /
• pp.831-843
• /
• 2015

This study estimates MODIS-derived evapotranspiration data quality by revised RS-PM algorithm in Seolmacheon test basin. We used latent flux with eddy covariance method to evaluate MODIS-derived spatial evapotranspiration and gap-filled these data by three methods (FAO-PM, MDV and Kalman Filter) and to quantify daily evapotranspiration. Gap-filled daily evapotranspiration data was used to evaluate evapotranspiration computed by revised RS-PM algorithm derived MODIS satellite images. For the water budget analysis, we used soil moisture content that is quantified to average individual soil moisture rate observed by TDR (Time Domain Reflectometry) sensor at soil depth. The soil moisture variation is calculated in consideration from initial to final soil moisture content. According to the result of this study, evapotranspiration computed by revised RS-PM algorithm is very larger than eddy covariance data gap-filled by three methods. Also, water budget characteristics is not closed. We could analysis that MODIS-derived spatial evapotranspiration does not represent actual evapotranspiration in Seolmacheon.

• The Journal of Engineering Geology
• /
• v.18 no.2
• /
• pp.191-196
• /
• 2008

This study is a case study for application of the RTI warning model to Korea which was previously developed to predict landslide potential and occurrence time during a rainfall event. The rainfall triggering index (RTI) is defined as the product of the rainfall intensity I (mm/hr) and the effective accumulated rainfall $R_t$ (mm). This index is used to evaluate the landslide and debris-flow occurrence potential at time t during a rainfall event. The upper critical value ($RTI_{UC}$) of RTI and the lower critical value ($RTI_{LC}$) of RTI can be determined by historical rainfall data of a certain area. When the rainfall intensity exceeds the upper critical value, there are high potential to occur land-slides. The analysis result can predict landslide occurrence time of an area during a rainfall event as well as land-slide potential. The result can also be used as an important data to issue early-warning of landslides. In order to apply the RTI warning model to Korea this study analyzed rainfall data and landslides data in Inje county, Gangwon province, Korea from July 13 to July 19, 2006. According to the analysis result, the rainfall intensity exceeded the upper critical value 23 hours ago, 11 hours ago, and 9 hours ago from 11:00 in the morning, July 16. Therefore, landslide warnings would be issued three times for people evacuation for avoiding or reducing hurts and dam-ages from landslides in mountainous areas of Inje.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.104-104
• /
• 2018

이수안전도의 기준이 되는 갈수량에 대해 기후변화 시나리오에 따른 전망을 제시하였다. 충주 댐 유역을 대상으로 기준기간(1986~2000년)에서의 기상청의 관측 기상자료와 IPCC 보고서의 RCP 4.5/8.5 시나리오를 대상으로 CMIP5(Coupled Model Intercomparison Project Phase 5)에서 제공하는 기후변화 자료 중 5개의 모델(ACCESS1.3 CanESM2, CNRM-CM5, GFDL-ESM2G, HadGEM2-AO)의 기준기간과 미래기간(2011~2100년)의 기상자료를 수집하였다. 기후변화 자료는 정상성/비정상성 분위사상법과 베이지안 모델 평균기법을 통해 불확실성과 통계적 오차를 저감하였다. 미래기간에서, 강우는 RCP 4.5에서 1.74mm/year, RCP 8.5에서 3.22mm/year, 실제증발산은 RCP 4.5에서 1.09mm/year, RCP 8.5에서 1.78mm/year의 증가율을 보였다. 실제증발산을 입력자료로 활용할 수 있도록 IHACRES모델의 CMD(Catchment Moisture Deficit) 비선형 모듈의 매개변수를 변이하여 유효강우량 산정 과정을 개선하였다. 기준기간에서 관측유량자료와 IHACRES의 시뮬레이션을 통해 산정된 유량자료의 R-squared는 0.65이다. 기준기간에서의 매개변수를 고정하여 미래기간의 유량을 산정하고 유황분석을 통해 갈수량 전망하였다. 유량은 RCP 4.5에서 4.41MCM/year, RCP 8.5에서 9.66MCM/year의 증가율을 보였다. 갈수량은 RCP 4.5에서 0.30MCM/year, RCP 8.5에서 -0.47MCM/year의 증감율을 보였다. 연간 강수량 대비 실제증발산의 비율의 추세분석 결과, RCP 4.5에서는 홍수기에는 0.014%/year, 비홍수기에는 0.027%/year의 증가율을 보이며 거의 변화가 없는 추세를 확인할 수 있었다. RCP 8.5의 홍수기에는 -0.042%/year, 비홍수기에서는 0.167%/year의 증감율을 보이며 홍수기에는 실제증발산에 비해 강수량의 증가가 확연히 보였으며 비홍수기에는 강수량에 비해 실제증발산의 증가가 뚜렷이 확인되었다. RCP 8.5에서 비홍수기의 강수량 대비 실제증발산의 증가가 갈수량의 감소로 반영된 것을 확인할 수 있었다. 미래기간의 RCP 4.5/8.5에서 실제증발산의 증가로 인하여 강수량이 증가함에 따라 유입량이 증가함에도 불구하고 갈수량의 증가로 이어지지 않았다. 미래 갈수량의 감소는 하천의 건전성과 이수안전도의 위협이 될 수 있다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.32-32
• /
• 2018

최근 여러 가지 요인으로 가뭄이 빈발하고 있으며, 가뭄을 대비한 과학적 저수지 운영이 절실하다. 유입량, 관개용수량, 저수량, 하천유지유량 등 저수지 물수지를 반영하여 실제 가뭄 상황에 적용할 수 있는 시스템으로 개발하였다. 여기서, 하류 하천의 수량을 양수하여 저수량을 확보하는 양수저류를 고려하였고, 시기별 관개용수량을 간단관개, 절수관개 등의 실제 상황을 반영하도록 하였다. 또한 저수량의 장기간 변화를 관찰하여 저수지 운영의 가이드라인을 설정할 수 있도록 하였고, 하류 하천의 유량 변화도 평가할 수 있도록 하였다. 최근 수차례 가뭄을 겪은 충남 홍성에 위치한 대사저수지에 개발된 시스템을 적용하였다. 대사 저수지는 유역면적 $2.9km^2$, 유효저수량 137만$m^3$, 수혜면적 163ha에 이르며, 유역면적 $72.2km^2$인 하류하천의 와룡천으로부터 $0.057m^3/s$씩 양수하여 저수량을 확보하고 있다. 일별 저수율 자료가 있는 1991년부터 2016년까지 분석한 결과는 다음과 같다. 양수는 1월 15일부터 5월 31일까지 실시하는 것으로 하고 결과를 정리하였다. 첫째, 일 저수위를 모의하여 검증한 결과 일평균하여 관측 저수위는 EL.84.58m, 모의 저수위는 EL.85.87m이었다. 이 때 강우량은 연평균 1,275.2mm, 유입량은 718.0mm, 유출률 56.3%, 수면증발량 11.5만$m^3$, 관개용수 공급량 117.5만$m^3$, 월류량 148.9만$m^3$이었다. 둘째, 양수로 인한 유입량의 변화는 양수 전에는 연평균 209만$m^3$(유출률 56.3%)에서 양수 후 276만$m^3$(74.7%)로 증가하였고, 양수량은 67.5만$m^3$(연유입량의 32.3%)이었다. 셋째, 하류 와룡천의 유량은 양수 전에는 연평균 연유출량 5,200만$m^3$(유출률 56.5%)에서 양수 후 5,120만$m^3$(55.6%)으로 나타났다. 넷째, 양수 전에는 일평균 저수량이 47만$m^3$에서 양수 후 76만㎥으로 증가하였고, 양수저류로 인해 이수안전도는 15.4%에서 92.3%로 개선되었다. 또한 양수로 인해 저수지 유입량은 연평균 32.3% 증가하였고, 하류하천의 유량은 1.55% 감소하였다. 이상의 분석 결과로 양수저류는 가뭄대응에 상당한 효과가 있다고 평가할 수 있다. 또한 다양한 여건을 고려한 저수지 운영 가이드라인의 합리적 설정으로 보다 적극적인 가뭄대응이 필요하다고 본다. 물관리 현황은 지구별, 저수지별로 다양하다. 향후 현장 상황에 적합한 물관리 방법을 적극 모색해야 하며, 자연과 인간의 평등한 물 이용 환경조성에, 여기 개발한 도구가 일정 부분 유용할 것이라 판단한다.

• Journal of Korea Water Resources Association
• /
• v.52 no.4
• /
• pp.301-312
• /
• 2019

The importance of the dual drainage system model has increased as the urban flood damage has increased due to the increase of local storm due to climate change. The dual drainage model is a model for more accurately expressing the phenomena of surface flow and conduit flow. Surface runoff and pipe runoff are analyzed through the respective equations and parameters. And the results are expressed visually in various ways. Therefore, inundation analysis results of dual drainage model are used as important data for urban flood prevention plan. In this study, the applicability of the COBRA model, which can be interpreted by combining the dual drainage system with the natural watershed and the urban watershed, was investigated. And the results were compared with other dual drainage models (XP-SWMM, UFAM) to determine suitability of the results. For the same watershed, the XP-SWMM simulates the flooding characteristics of 3 types of dual drainage system model and the internal flooding characteristics due to the lack of capacity of the conduit. UFAM showed the lowest inundation analysis results compared with the other models according to characteristics of consideration of street inlet. COBRA showed the general result that the flooded area and the maximum flooding depth are proportional to the increase in rainfall. It is considered that the COBRA model is good in terms of the stability of the model considering the characteristics of the model to simulate the effective rainfall according to the soil conditions and the realistic appearance of the flooding due to the surface reservoir.

• Korean Journal of Soil Science and Fertilizer
• /
• v.15 no.4
• /
• pp.213-220
• /
• 1982

Soil water changes in lysimeters with four different soils and two different available soil depths were monitored during the growing seasons of the soybean-barley cropping from 1977 to 1980 in Suweon to evaluate evapotranspiration (ET) as a function of available soil water and evaporative demand of the atmosphere. ET was calculated with soil water profile and water balance. Soil water content was measured with a neutron moisture depth gauage and The evaporative demand of the atmosphere was estimated with a class A pan evaporation. Rainfall. solar radiation, and wind speed were observed to examine heat and water balances. The average ET of soybeans ranged from 1.6 mm/day at seedling to 6.5 mm/day at flowering, and that of barley ranged from 0.5 mm/day at the regrowth stage to 4.6 mm/day at heading; however, a large variability was observed. The ratio of ET to pan evaporation ($ET/E_o$) ranged from 0.5 to 1.1 for soybeans and 0.4 to 1.2 for barley. The soil evaporation factor ($K_e$) of the $ET/E_o$ component decreased as the soil water depleted and the canopy developed. The crop transpiration factor ($K_t$), another component of $ET/E_o$, also was a function of time and the soil water. $K_t$ was constant when the available soil water fraction (f) in the root zone was greater than a threshold value, and $K_e$ was decreased linearly when f was lower than this threshold. The threshold was 0.7 for the moderate evaporative demand days, 0.4 to 0.5 for the low evaporative demand days, and 0.9 to 0.96 for the high evaporative demand days. Conclusively, the ET can be estimated from the evaporative demand of the atmosphere, $E_o$, $K_e$ and $K_t$, and the available soil water content in the root zone.

• Journal of Korean Society of Forest Science
• /
• v.33 no.1
• /
• pp.1-32
• /
• 1977

This study has been made to find out more effective way of vegetation establishment on severely denuded forest land from the viewpoint of soil moisture regimes. Various environmental factors were measured to estimate soil moisture conditions of different sites. Soil moisture influence on growth of over vegetations, water requirement and drought resistance were analyzed. The efficiency of water use was also reckoned at different fertility levels and different soil moisture conditions. This research is composed of field experiment and green house experiment. Field experiment includes height growth, survival and coverage analysis of cover vegetations (Robinia pseudoacacia L., Lespedeza bicolor Turcz, Arundinella hirta Tanaka var. ciliare Koidzumi.) with 4 fertility level treatments on 3 slopes (Steep: $37^{\circ}$, Moderate: $25^{\circ}$, Gentle; $17^{\circ}$) during dry season (1 April-30 June) and wet season (1 July-10 September). At the same time temperature, relative humidity and precipitation were measured to understand the environmental changes. Soil moisture conditions were measured with soil moisture meter with 24 soil cells. Green house experiment comprised height, fresh weight and dry weight measurements of cover vegetations with 4 fertility levels and 3 moisture conditions for 70 days. The results extracted from experiments are as follews. 1. Cover vegtations have 3 patterns of water requirement at the early stage of growth. a) Robinia type has high water requirement and weaker drought resistance. b) Lespedeza type has low water requirement and stronger drought resistance. c) Arundinella type has moderate water requirement and weaker drought resistance. 2. The vegetations have different optimum fertility levels in different soil moisture supply condition. a) Robinia needs a low fertility level in dry condition and a high level in wet condition. b) Lespedeza needs only low fertility level in all conditions. c) Arundinella needs a low fertility level in dry condition and a high level in wet condition. 3. The efficiency of water use (Water/1g dry weight) by fertility levels is different from one another. Robinia and Arundinella have a good efficiency at low fertility level in dry condition and at high fertility level in wet condition. Lespedeza has a good efficiency at low fertility level in all conditions. 4. $P_2O_5$ requirement of Robinia and Lespedeza is high, but that of Arundinella is low. Soil moisture condition has a great influence on $P_2O_5$ absorption in dendued forest land. Once Vegetations are established on suitable sites with optimum fertitity level according to different moisture condition, even the small amount of soil water in denuded land can he used with high efficiency and the effect of fertility treatment can be maximized.

• Korean Journal of Environmental Agriculture
• /
• v.22 no.1
• /
• pp.16-25
• /
• 2003

Manun Reservoir, located in Andong district has the capacity of 2 million tons in irrigation water supply with the drainage area of $23.8\;km^2$. Manun Reservoir is over fifty year old, and shallow in depth. The ratio of drainage area (DA) to reservoir surface area (SA) as an effective physical parameter on water quality was 56.1 and was higher than those of other agricultural reservoirs. The ratio of reservoir storage (ST) to SA in Manun Reservoir was 4.79, and the mean depth was below 8m. Both ratios of DS/SA, total area (TA)/ST and ST/SA in Manun Reservoir were relatively higher than those in other agricultural reservoir and natural lakes in Korea. These physical parameters in Manun Reservoir, however, had a eutropic potential significance. Average of COD, IN, and TP in Manun Reservoir were 11.1 mg/L 1.426 mg/L, 0.093 mg/L, respectively. In the inflow stream of Manun Reservoir, the TN ($1.426{\sim}3.809\;mg/L$) was higher than those in reservoir. Only Lyngbya spp. was dominant in phytoplankton for this study period and Gymnodinium spp., Peridinium spp., and Cryptomonas spp. were dominant in zooplankton. According to the Carlson's trophic status index, Mnnun Reservoir was eutrophic in 1996, 1997, and 1999, and hypertrophic in 1998.

• Water for future
• /
• v.28 no.6
• /
• pp.147-158
• /
• 1995

The purpose of this study is to establish a method of estimating the daily urban water demand using statistical model. This method will be used for the development of the efficient management and operation of the water supply facilities. The data used were the daily urban water use, the population, the year lapse and the weather conditions such as temperature, precipitation, relative humidity, etc. Kwangju city was selected for the case study area. The raw data used in this study were rearranged either by month or by season for the purpose of analysis, and the statistical analysis was applied to the data to obtain the regression model. As a result, the multiple linear regression model was developed to estimate the daily urban water use based on the seather condition. The regression constant and the model coefficients were determined for each month of a year. The accuracy of the model was within 3% of average error and within 10% of maximum error. The developed model was found to be useful to the practical operation and management of the water supply facilities.