Developing reliable soil moisture prediction techniques at agricultural regions is a pivotal issue for sustaining stable crop productions. In this study, a physically-based SWAP(Soil-Water-Atmosphere-Plant) model was suggested to estimate soil moisture dynamics at the study sites. ROSETTA was also integrated to derive the soil hydraulic properties(α, n, θr, θs, Ks) as the input variables to SWAP based on the soil information(Sand, Silt and Clay-SSC, %). In order to predict the soil moisture dynamics in future, the mid-term TIGGIE(THORPEX Interactive Grand Global Ensemble) and long-term S2S(Subseasonal to Seasonal) weather forecasts were used, respectively. Our proposed approach was tested at the six study sites of RDA(Rural Development Administration). The estimated soil moisture values based on the SWAP model matched the measured data with the statistics of Root Mean Square Error(RMSE: 0.034∼0.069) and Temporal Correlation Coefficient(TCC: 0.735∼0.869) for validation. When we predicted the mid-/long-term soil moisture values using the TIGGE(0∼15 days)/S2S(16∼46 days) weather forecasts, the soil moisture estimates showed less variations during the TIGGE period while uncertainties were increased for the S2S period. Although uncertainties were relatively increased based on the increased leading time of S2S compared to those of TIGGE, these results supported the potential use of TIGGE/S2S forecasts in evaluating agricultural drought. Our proposed approach can be useful for efficient water resources management plans in hydrology, agriculture, etc.
Pollutant Delivery Ratio of Okdong-cheon Watershed Using HSPF Model
이현지 Lee Hyunji , 김계웅 Kim Kyeung , 송정헌 Song Jung-hun , 이도길 Lee Do Gil , 이한필 Rhee Han-pil , 강문성 Kang Moon Seong
The primary objective of this study was to analyze the delivery ratio using Hydrological Simulation Program - Fortran (HSPF) in Okdong-cheon watershed. Model parameters related to hydrology and water quality were calibrated and validated by comparing model predictions with the 8-day interval filed data collected for ten years from the Korea Ministry of Environment. The results indicated that hydrology and water quality parameters appeared to be reasonably comparable to the field data. The pollutant delivery loads of the watershed in 2015 were simulated using the HSPF model. The delivery ratios of each subwatershed were also estimated by the simple ratio calculation of pollutant discharge load and pollutant delivery load. Coefficients of the regression equation between the delivery ratio and specific discharge were also computed using the delivery ratio. Based on the results, multiple regression analysis was performed using the discharge and the physical characteristics of the subwatershed such as the area. The equation of delivery ratio derived in this study is only for the Okdong-cheon watershed, so the larger studies are needed to apply the findings to other watersheds.
Analysis of Drought Risk in the Upper River Basins based on Trend Analysis Results
정일원 Il Won Jung , 김동영 Dong Yeong Kim , 박지연 Jiyeon Park
This study analyzed the variability of drought risk based on trend analysis of dry-seasonal dam inflow located in upper river basins. To this, we used areal averaged precipitation and dam inflow of three upper river dams such as Soyang dam, Chungju dam, and Andong dam. We employed Mann-Kendall trend analysis and change point detection method to identify the significant trends and changing point in time series. Our results showed that significant decreasing trends (95% confidence interval) in dry-seasonal runoff rates (= dam inflow/precipitation) in three-dam basins. We investigated potential causes of decreasing runoff rates trends using changes in potential evapotranspiration (PET) and precipitation indices. However, there were no clear relation among changes in runoff rates, PET, and precipitation indices. Runoff rate reduction in the three dams may increase the risk of dam operational management and long-term water resource planning. Therefore, it will be necessary to perform a multilateral analysis to better understand decreasing runoff rates.
Development of Hydroclimate Drought Index (HCDI) and Evaluation of Drought Prediction in South Korea
류재현 Ryu Jaehyun , 김정진 Kim Jungjin , 이경도 Lee Kyungdo
The main objective of this research is to develop a hydroclimate drought index (HCDI) using the gridded climate data inputs in a Variable Infiltration Capacity (VIC) modeling platform. Typical drought indices, including, Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and Self-calibrated Palmer Drought Severity Index (SC-PDSI) in South Korea are also used and compared. Inverse Distance Weighting (IDW) method is applied to create the gridded climate data from 56 ground weather stations using topographic information between weather stations and the respective grid cell (12 km x 12 km). R statistical software packages are used to visualize HCDI in Google Earth. Skill score (SS) are computed to evaluate the drought predictability based on water information derived from the observed reservoir storage and the ground weather stations. The study indicates that the proposed HCDI with the gridded climate data input is promising in the sense that it can help us to predict potential drought extents and to mitigate its impacts in a changing climate. The longer term drought prediction (e.g., 9 and 12 month) capability, in particular, shows higher SS so that it can be used for climate-driven future droughts.
Analysis of Baseflow using Future Land Use and Climate Change Scenario
최유진 Choi Yujin , 김종건 Kim Jonggun , 이동준 Lee Dong Jun , 한정호 Han Jeongho , 이관재 Lee Gwanjae , 박민지 Park Minji , 김기성 Kim Kisung , 임경재 Lim Kyoung Jae
Since the baseflow, which constitutes most of the river flow in the dry season, plays an important role in the solution of river runoff and drought, it is important to accurately evaluate the characteristics of the baseflow for river management. In this study, land use change was evaluated through time series data of land use, and then baseflow characteristics were analyzed by considering climate change and land use change using climate change scenarios. The results showed that the contribution of baseflow of scenarios considering both climate change and land use change was lower than that of scenarios considering only climate change for yearly and seasonal analysis. This implies that land use changes as well as climate changes affect base runoff. Thus, if we study the watershed in which the land use is occurring rapidly in the future, it is considered that the study should be carried out considering both land use change and climate change. The results of this study can be used as basic data for studying the baseflow characteristics in the Gapcheon watershed considering various land use changes and climate change in the future.
Short Term Drought Forecasting using Seasonal ARIMA Model Based on SPI and SDI - For Chungju Dam and Boryeong Dam Watersheds -
윤영선 Yoon Yeongsun , 이용관 Lee Yonggwan , 이지완 Lee Jiwan , 김성준 Kim Seongjoon
In this study, the SPI (Standardized Precipitation Index) of meteorological drought and SDI (Streamflow Drought Index) of hydrological drought for 1, 3, 6, 9, and 12 months duration were estimated to analyse the characteristics of drought using rainfall and dam inflow data for Chungju dam (6,661.8 km2) with 31 years (1986-2016) and Boryeong dam (163.6 km2) watershed with 19 years (1998-2016) respectively. Using the estimated SPI and SDI, the drought forecasting was conducted using seasonal autoregressive integrated moving average (SARIMA) model for the 5 durations. For 2016 drought, the SARIMA had a good results for 3 and 6 months. For the 3 months SARIMA forecasting of SPI and SDI, the correlation coefficient of SPI3, SPI6, SPI12, SDI1, and SDI6 at Chungju Dam showed 0.960, 0.990, 0.999, 0.868, and 0.846, respectively. Also, for same duration forecasting of SPI and SDI at Boryeong Dam, the correlation coefficient of SPI3, SPI6, SDI3, SDI6, and SDI12 showed 0.999, 0.994, 0.999, 0.880, and 0.992, respectively. The SARIMA model showed the possibility to provide the future short-term SPI meteorological drought and the resulting SDI hydrological drought.
Evaluation of Wind Load and Drag Coefficient of Insect Net in a Pear Orchard using Wind Tunnel Test
송호성 Song Hosung , 유석철 Yu Seok-cheol , 김유용 Kim Yu Yong , 임성윤 Lim Seong-yoon
Fruit bagging is a traditional way to produce high-quality fruit and to prevent damage from insects and diseases. Growing pears by non-bagging is concerned about the damage from insect, it can be controlled by installing a insect net facility. Wind load should be considered to design the insect net facility because it has the risk of collapse due to the strong wind. So we carried out wind tunnel test for measurement of drag force, where the insect net with porosity about 65% is selected as an experimental subject. As a result of the test, drag force was measured to be 244.14 N when insect net area and wind speed are 1 ㎡ and 22.7 m/s respectively. And, drag coefficients for the insect net were found to be about 0.55∼0.57, which may be used as the preliminary data to design the insect net facilities at the orchard.
Life Cycle CO2 Assessment and Domestic Applicability Evaluation of the Drainage Material for Reclaimed Land Using Oyster Shell
전지훈 Jeon Jihun , 손영환 Son Younghwan , 김동근 Kim Donggeun , 김태진 Kim Taejin
The objective of this study is to assess the environmental effect of the reclaimed land drainage method using oyster shell through the Life cycle CO2 assessment, and to evaluate the applicability in South Korea. In this Study, the life cycle CO2 emissions of oyster shell (OS) and crushed stone (CS, as avoided product) were assessed and compared. The Life Cycle Assessment method was used for quantitative evaluation of direct or indirect environmental effects of OS recycling. CO2 was selected as the evaluation target material, and the scope of assessment includes the acquisition of materials, processing, transportation, construction phases. Compared to using CS, 77.0% of CO2 emissions in acquisition and processing, 47.0% in transportation and 6.5% in construction phase were reduced, respectively by using of OS. The maximum transportation distance of OS was estimated according to transportation distance of CS. OS has environmental advantages than CS within about 26 - 101 km from the source. OS was found to be applicable to reclaimed lands up to 810 ha, 3,910 ha from Tongyeong and Yeosu, respectively. In addition, the amount of OS that could be used as drainage material for reclaimed land was much higher than annual OS production of South Korea. Therefore, it is considered that OS is sufficient to be used as drainage material for reclaimed land in South Korea.
Estimating Reference Crop Evapotranspiration Using Artificial Neural Network and Temperature-based Climatic Data
이성학 Lee Sung-hack , 김마가 Kim Maga , 최진용 Choi Jin-yong , 방재홍 Bang Jehong
Evapotranpiration (ET) is one of the important factor in Hydrological cycle and irrigation planning. In this study, temperature-based artificial neural network (ANN) model for daily reference crop ET estimation was developed and compared with reference crop evapotranpiration (ET0) from FAO-56 Penman-Monteith method (FAO-56 PM) and parameter regionalized Hargreaves method. The ANN model was trained and tested for 10 weather stations (5 inland stations and 5 costal stations) and two input climate factors, maximum temperature (Tmax), minimum temperature (Tmin), and extraterrestrial radiation (RA) were used for training and validation of temperature-based ANN model. Monthly reference ET by the ANN model also compared with parameter regionalized Hargreaves method for ANN model applicability evaluation. The ANN model evapotranspiration demonstrated more accordance to FAO-56 PM evapotranspiration than the ET0 from parameter regionalized Hargreaves method(R-Hargreaves). The results of this study proposed that daily reference crop ET estimated by the ANN model could be used in the condition of no sufficient climate data.
Outlier Detection of Real-Time Reservoir Water Level Data Using Threshold Model and Artificial Neural Network Model
김마가 Kim Maga , 최진용 Choi Jin-yong , 방재홍 Bang Jehong , 이재주 Lee Jaeju
Reservoir water level data identify the current water storage of the reservoir, and they are utilized as primary data for management and research of agricultural water. For the reservoir storage management, Korea Rural Community Corporation (KRC) installed water level stations at around 1,600 agricultural reservoirs and has been collecting the water level data every 10 minutes. However, various kinds of outliers due to noise and erroneous problems are frequently appearing because of environmental and physical causes. Therefore, it is necessary to detect outlier and improve the quality of reservoir water level data to utilize the water level data in purpose. This study was conducted to detect and classify outlier and normal data using two different models including the threshold model and the artificial neural network (ANN) model. The results were compared to evaluate the performance of the models. The threshold model identifies the outlier by setting the upper/lower bound of water level data and variation data and by setting bandwidth of water level data as a threshold of regarding erroneous water level. The ANN model was trained with prepared training dataset as normal data (T) and outlier (F), and the ANN model operated for identifying the outlier. The models are evaluated with reference data which were collected reservoir water level data in daily by KRC. The outlier detection performance of the threshold model was better than the ANN model, but ANN model showed better detection performance for not classifying normal data as outlier.
Irrigation Water Requirements for Upland Crops Using Rainfall Data and Water Management Guidelines
최용훈 Choi Yonghun , 김영진 Kim Youngjin , 김용원 Kim Yongwon , 김민영 Kim Minyoung , 전종길 Jeon Jonggil
The purpose of this study is to determine the amount of irrigation water for upland crop growth based on the 30 year of historical rainfall data and the water management guidelines as a reference. Five regions and ten crops were selected by their cultivation size. The changes of soil moisture contents were calculated using daily mean rainfall and irrigation demand. This study assumed that crops are irrigated when the soil moisture contents fell below of the field capacity for more than 5 days, which is the drought condition defined by RDA. The maximum irrigation water requirements was 167.2 mm for chinese cabbage during the growing season, which was followed by corn (112.0 mm), daikon (102.3 mm), spinach (66.1 mm), lettuce (56.7 mm), pepper (46.5 mm), potato (33.9 mm), sweet tomato (27.4 mm), peanut (11.5 mm) and bean (10.3 mm), The results of this study could contribute to providing valuable data to determine the capacity of irrigation facilities and to establish the emergency operation plans under extreme unfavorable weather condition (heat wave, etc.) for crop growth.
Determination of Hydrophyte Index of Native Plant on the Downstream Slope of Earth Fill Dam
김현수 Kim Hyun Soo , 류범희 Ryu Bum Hee , 박승기 Park Seung Ki
The purpose of study was to determine the hygrophyte index of each plant(HIP) considering the moisture environment condition (MEC) of the native plants on the downstream slope of the fill dam and evaluate its applicability which to develop a method to search for leaks and saturated zones of the fill dam for status evaluation of precision safety diagnosis. The HIP was weighted average and consisted of 19 ranks. The weighted average was calculated according to the following three procedures: First, the linear assumption was made according to the actual habitat environmental conditions, the second one was weighted to 10% of the optimal habitat condition, and finally the average value of the distribution range values. The Hygrophyte index of vegetation at each plot (HIV) was obtained from the Sinheung reservoir (Yesan-gun, Chungcheongnam-do) using the results of vegetation survey of the Sinheung reservoir with precision safety diagnosis and suggested the use of the hygrophyte index of the cultivated vegetation. The average HIP range of plant species that emerged in 50 survey sites on the downstream slope of the Sinheung reservoir is 2.99 to 3.56. The coefficient of variation showed a large difference depending on the appearance of the leakage indicator plant(LIP) species. The range of HIV is 2.80 to 4.26, the mean value is 3.37, standard deviation is 0.37 and the coefficient of variation is 9.7%. As a result, the value of the coefficient of variation showed a large difference depending on the appearance of the plant species.
Comparative Evaluation of Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) for Meteorological Drought Detection over Bangladesh
모하마드캄루자먼 Kamruzzaman M. , 조재필 Cho Jaepil , 장민원 Jang Min-won , 황세운 Hwang Syewoon
Comparative Evaluation of Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) for Meteorological Drought Detection over Bangladesh
모하마드캄루자먼 Kamruzzaman M. , 조재필 Cho Jaepil , 장민원 Jang Min-won , 황세운 Hwang Syewoon
A good number of drought indices have been introduced and applied in different regions for monitoring drought conditions, but some of those are region-specific and have limitations for use under other climatic conditions because of the inherently complex characteristics of drought phenomenon. Standardized Precipitation Index (SPI) indices are widely used all over the world, including Bangladesh. Although newly developed, studies have demonstrated The Effective Drought Index (EDI) to perform better compared to SPIs in some areas. This research examined the performance of EDI to the SPI for detecting drought events throughout 35 years (1981 to 2015) in Bangladesh. Rainfall data from 27 meteorological stations across Bangladesh were used to calculate the EDI and SPI values. Results suggest that the EDI can detect historical records of actual events better than SPIs. Moreover, EDI is more efficient in assessing both short and long-term droughts than SPIs. Results also indicate that SPI3 and the EDI indices have a better capability of detecting drought events in Bangladesh compared to other SPIs; however, SPI1 produced erroneous estimates. Therefore, EDI is found to be more responsive to drought conditions and can capture the real essence of the drought situation in Bangladesh. Outcomes from this study bear policy implications on mitigation measures to minimize the loss of agricultural production in drought-prone areas. Information on severity level and persistence of drought conditions will be instrumental for resource managers to allocate scarce resources optimally.
