농촌 소하천에서의 재폭기계수 추정

학위논문(석사)--서울대학교 대학원 :농공학과 농업토목전공,2001.Maste

Estimation of an Optimum Ecological Stream Flow in the Banbyeon Stream Using PHABSIM - Focused on Zacco platypus and Squalidus chankaensis tsuchigae -

The objective of this study was to estimate an optimum ecological flow rate in the Banbyeon stream based on the two representative fish species.Hydraulic stream environment was simulated with HEC-RAS for two water flow regimes and used for the PHABSIM hydraulic simulation. A dominantspecies of Zacco platypus and an endemic species of Squalidus chankaensis tsuchigae were selected as the representative fishes whose habitat conditionswere evaluated for the spawning and adult stages. Weighted usable area (WUA) was estimated based on habitat suitability index (HSI) and PHABSIMhabitat simulation. Overall deep water zone in the stream demonstrated greater WUA which implies better habitat status. The estimated WUA for Zaccoplatypus as the dominant species was about five times greater than Squalidus chankaensis tsuchigae at the stream flow of 12 m³/s. The optimumecological flow rates were 15 m³/s and 25 m³/s for the respective spawning and adult stages of Zacco platypus, while 5 m³/s was estimated for boththe life cycles of Squalidus chankaensis tsuchigae. Assuming that the dominant species may survive better in wider flow regimes, the optimumecological flow rate should be determined rater based on the endemic species and flow rate of 5 m³/s was suggested for the Banbyeon stream.N

Optimization of Storage Tank Installation Locations for Pipeline Water Supply Using Genetic Algorithm

Rice paddy has been actively converted into upland crop fields as more profitable upland crop cultivation are encouraged along with the decrease inrice consumption. However, the current water supply system remains mainly for paddy water supply, so research on pipeline water supply for uplandcultivation is needed. The objective of this study was to optimize storage tank installation locations for pipeline water supply in reservoir irrigationdistricts. Five of reservoir irrigation districts were selected as the study sites and gridded of 10×10 m in size. Then genetic algorithm was adopted toevaluate the effects of spatial storage tank allocation on total pipeline cost. The lengths of the main and branch pipelines were considered as theobjective cost function for the optimization of storage tank installation. Overall the shorter the branch pipeline and the longer the main pipeline, asthe number of storage tanks increase. The minimal pipeline cost, i.e., optimal condition was reached when approximately 10% of the storage tanknumbers to total upland plots were installed. The methodology presented in this study can be applied to determine the number and spatial arrangementof storage tanks for upland pipeline irrigation system design.N

Application of Drone Images to Investigate Biomass Management Practices and Estimation of CH4 Emissions from Paddy Fields

Rice paddy cultivation is one of the major sources in methane (CH4) emission of which accurate assessment would be a prerequisite for agriculturalgreenhouse gas management. Biomass treatment in paddy fields is an important factor that affects CH4 emissions and thus needs to be taken intoaccount. The objectives of this study were to apply drone images to investigate organic matter practices and to incorporate into the estimation of CH4emissions from paddy fields. Three study areas were selected by one from each of the three different regions of Yeongnam, Honam and Jungbu, whichare the most active region in paddy cultivation. The eBee drone was used to take images of the study sites twice a year; Jul mid-season for identifyingrice cultivation area; Jan for investigating rice straw management and winter crop cultivation. Based on biomass management practices, differentemissions factors were assigned on an individual paddy field and CH4 emmisions were estimated by multiplying respective areas. The ratios of ricestraw application and winter crop cultivation were 1.4% and 37.2% in Hapcheon, 1.3% and 19.8% in Gimje, and 0.0% and 0.5% in Dangjin,respectively. The CH4 emissions estimates for respective sites were 0.40 ton CH4/year/ha, 0.34 ton CH4/year/ha, and 0.29 ton CH4/year/ha. On average,estimated CH4 emissions of this study were 28.5% less than the current Tier 2 CH4 emission estimation method.N

Physical Habitat Assessment of Bokha Downstream Reach Considering Life Cycle Stages of Zacco platypus Using PHABSIM

The objectives of this study were to assess physical habitat suitability of fish species for different life cycle stages and to suggest appropriate ecologicalstream flows in a Bokha downstream reach. A dominant species of Zacco platypus was selected as the study fish of which three stages of spawning,juvenile and adult in life cycle were considered into assessment. The stream hydraulic environment was calibrated with HEC-RAS before the PHABSIMsimulation. The hydraulics of flow velocity and depth were used to estimate Weighted Usable Area (WUA) by multiplying respective habitat suitabilityindices with stream area. Overall the WUAs tend to be great in gentle slopes with relatively shallow water depth regions. Maximum WUAs, ie,candidate for ecological flow rates were 1 m3/s, 7 m3/s and 8 m3/s for the respective spawning, juvenile and adult stages of Zacco platypus. Sincethe ecological flow rates for juvenile and adult stages appeared to be is greater than the abundant flow rate (3.67 m3/s) for the study reach, additionalwater supply may be needed but should be cautious to avoid the spawning period of Apr through May from the stream water management perspective.N

Evaluation of Water Supply Stability for Upland Crop in Reservoir Irrigation Districts

As the agricultural land use shifts from paddy to upland, ensuring reservoir water supply stability for upland crop irrigation becomes essential. The objectives of this study were to estimate the irrigation water requirements considering the upland irrigation scenario and to evaluate the reliability of the water supply from the agricultural reservoir using resilience indexes. Two study sites, Sinheung and Hwajeong, were selected, and soybean and red peppers, the most water-intensive crops, were selected as study crops, respectively. For the irrigation scenario, two irrigation methods of traditional scheduling (which irrigates all sites at once) and rotational scheduling (which distributes irrigation by districts), along with the upland conversion rate, were considered. The net irrigation requirement was estimated through a water balance analysis. The stability of the reservoir was evaluated using resilience indexes based on the simulated 10-years reservoir water levels and drought criterion. Overall, the water supply of the reservoir was evaluated as stable during the simulated 10 years, except for the one year. Compared to the two irrigation methods, rotational scheduling resulted in lower irrigation water usage in both sites, with reductions of 1.6%, and 0.3%, respectively. As the upland conversion rate increases, the water deficit could be intensified in Hwajeong with a conversion rate exceeding 50%, showing the number of deficit(ND) over the one and a rapid increase in the deficit ratio(DR). It was confirmed that the reservoir operation criteria can be enhanced by incorporating resilience indicators along with crop growth information, thus, this will be a further study.N

Classification of Summer Paddy and Winter Cropping Fields Using Sentinel-2 Images

Up-to-date statistics of crop cultivation status is essential for farm land management planning and the advancement in remote sensing technology allowsfor rapid update of farming information. The objective of this study was to develop a classification model of rice paddy or winter crop fields basedon NDWI, NDVI, and HSV indices using Sentinel-2 satellite images. The 18 locations in central Korea were selected as target areas and photographedonce for each during summer and winter with a eBee drone to identify ground truth crop cultivation. The NDWI was used to classify summer paddyfields, while the NDVI and HSV were used and compared in identification of winter crop cultivation areas. The summer paddy field classification withthe criteria of –0.195<NDWI<0.15 was 90.9% accurate on average when compared with ground truth. Model performance for the winter crop fieldclassification was also excellent showing the accuracy greater than 98.2% on average for both models. However, cloud and greenhouses appeared todemonstrate optical similarity with paddy in the NDWI values, implying additional caution should be taken when removing cloud and greenhouseeffects. Overall the developed methods for paddy and winter crop classification performed reasonably well at the irrigation district level and furtherstudies are needed to investigate model performance at regional or national scales.N

Comparative Analysis of DTM Generation Method for Stream Area Using UAV-Based LiDAR and SfM

Gaining an accurate 3D stream geometry has become feasible with Unmanned Aerial Vehicle (UAV), which is crucial for better understanding streamhydrodynamic processes. The objective of this study was to investigate series of filters to remove stream vegetation and propose the best method forgenerating Digital Terrain Models (DTMs) using UAV-based point clouds. A stream reach approximately 500 m of the Bokha stream in Icheon citywas selected as the study area. Point clouds were obtained in August 1st, 2023, using Phantom 4 multispectral and Zenmuse L1 for Structure fromMotion (SfM) and Light Detection And Ranging (LiDAR) respectively. Three vegetation filters, two morphological filters, and six composite filters whichcombined vegetation and morphological filters were applied in this study. The Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) wereused to assess each filters comparing with the two cross-sections measured by leveling survey. The vegetation filters performed better in SfM, especiallyfor short vegetation areas, while the morphological filters demonstrated superior performance on LiDAR, particularly for taller vegetation areas. Overall,the composite filters combining advantages of two types of filters performed better than single filter application. The best method was the combinationof Progressive TIN (PTIN) and Color Indicies of Vegetation Extraction (CIVE) for SfM, showing the smallest MAE of 0.169 m. The proposed methodin this study can be utilized for constructing DTMs of stream and thus contribute to improving the accuracy of stream hydrodynamic simulations.N

Economic Analysis of Upland Crop Irrigation Between Individual and Collective Well Water Supply

밭은 논에 비해 수익성이 높고 경작면적도 증가 추세에 있어 적절한 용수공급의 중요성이 커지는데도, 밭 용수기반은 부족한 상황이다. 본 연구의 목적은 밭 재배지의 공간분포에 따른 개별관정과 집단관정에 의한 밭 용수공급의 경제성을 비교 평가하는데 있다. 노지 밭작물 중 고추, 배추, 사과, 콩 네 작물에 대해 충청권역에서 각 작물의 주요 생산지역인 청양군, 당진시, 예산군, 괴산군을 대상지역으로 선정하였다. 경제성 분석 결과, 고추, 배추, 사과 콩의 B/C ratio는 개별관정 시나리오에서 1.49, 1.36, 1.90, 0.71, 집단관정 시나리오에서 1.45, 1.20, 1.91, 0.65로 산정되어 콩을 제외한 고추, 배추, 사과는 밭 용수공급시설의 개발이 경제적 타당성이 있는 것으로 나타났다. 특히 작물의 가치가 큰 사과와 고추재배의 경우 밭용수 공급의 효과가 커서 작물가치가 관정개발의 중요한 인자로 나타났다. 작물 총수입에 대하여 민감도 분석을 수행한 결과 작물의 총수입이 낮은 작물일수록 가격변동이 경제성에 미치는 영향이 큰 것으로 나타났다. 집단관정 개발을 위한 필지 수에 따라 경제성 분석을 수행한 결과 고추와 배추의 경우 밭의 공간분포가 밀집되지 않아 집단관정 개발 시 규모의 경제 효과가 나타나지 않았으며, 사과와 콩의 경우 20개 이상의 필지를 집단화한 경우 규모의 경제의 효과가 나타났다. 결론적으로, 관정을 이용한 용수개발은 작물가치가 큰 사과나 고추 작물에 유리하고, 집단관정의 효과는 실제 작물 재배의 공간분포자료를 바탕으로 추가적인 분석이 요구된다. Profitability of upland crops is better than paddy crops and proportion of upland is increasing. However, there is a lack of infrastructures for upland irrigation. The object of this study were to develop water supply scenarios using individual and collective agricultural wells to evaluate economic feasibility to consider geographical analysis of upland farms and water supply facilities. Cheongyang, Dangjin, Yesan, and Goesan were selected as study areas where four different crops of red pepper, chinese cabbage, apple, and bean, respectively, were mainly produced in Chungcheong province. As a result, B/C ratio was estimated as 1.49, 1.36, 1.90, and 0.71 in using individual wells scenario, and 1.45, 1.20, 1.91, and 0.65 in using collective wells scenario for red pepper, chinese cabbage, apple, and bean. It turned out that change of price effected on economic feasibility a lot for crops with low production income. As a result of evaluating economic feasibility by number of plots for developing collective well, there was no effect of economy of scale for red pepper and chinese cabbage. In case of collectivizating more than 20 upland plots, effect of economy of scale appeared for apple and bean. In conclusion, development of water using high value crops including red pepper and apple, and effect of collective well requires additory analysis of .spatial distribution of farms.N