• Environmental Engineering Research
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• v.11 no.4
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• pp.194-200
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• 2006

Recently, the population growth, industrial and agricultural development are rapidly undergoing in the Lower Rio Grande Valley (LRGV) in Texas. The Lower Rio Grande Valley (LRGV) composed of the 4 counties and three of them are interesting for Non-point and point source pollutant modeling: Starr, Cameron, and Hidalgo. Especially, the LRGV is an intensively irrigation region, and Texas A&M University Agriculture Program and the New Mexico State University College of Agriculture applied irrigation district program, projects in GIS and Hydrology based agricultural water management systems and assessment of prioritized protecting stream network, water quality and rehabilitation based on water saving potential in Rio Grande River. In the LRGV region, where point and non-point sources of pollution may be a big concern, because increasing fertilizers and pesticides use and population cause. This project objective seeks to determine the accumulation of non-point and point source and discuss the main impacts of agriculture and environmental concern with water quality related to pesticides, fertilizer, and nutrients within LRGV region. The GIS technique is widely used and developed for the assessment of non-point source pollution in LRGV region. This project shows the losses in $kg/km^2/yr$ of BOD (Biological Oxygen Demand), TN (total Nitrogen) and TP (total phosphorus) in the runoff from the surface of LRGV. Especially, farmers in Cameron County consume a lot of fertilizer and pesticide to improve crop yield net profit. Then, this region can be created as larger nonpoint source area for nutrients and the intensity of runoff by excess irrigation water. And many sediment and used irrigation water with including high nutrients can be discharged into Rio Grade River.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.21-28
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• 2013

The objective of the study was to investigate the effect of rice straw mat, rice straw mat with PAM (Polyacrylamide) and gypsum addition on surface runoff and sediment discharge in field. Six experimental plots of $5{\times}22m$ in size and 3 % in slope prepared on gravelly sandy loam soil were treated with control, rice straw mat cover with gypsum and rice straw mat cover with gypsum and PAM. Radish in Spring and Chinese cabbage in autumn growing seasons were cultivated. Non point source (NPS) pollution discharge was monitored and compared among the treatments. Rainfall of the 10 monitored events ranged from 17.0 mm to 93.5 mm. Runoff coefficient of the events was 0.005~0.239 in control plot, 0~0.176 in rice straw plot with gypsum and 0~0.046 in rice straw mat plot with gypsum and PAM. When compared to the control plot, the runoff amount was reduced by 10.4~100 % (Ave. 60.8) in rice straw plot with gypsum and 80.7~100 % (Ave. 96.7 %) in rice straw mat plot with gypsum and PAM. The reduction of NPS pollution load was 54.6 % for BOD5, 71.5 % for SS, 41.6 % for TN and 61.4 % for T-P in rice straw with gypsum plot and 91.9 % for BOD5, 92.0 % for SS, 88.0 % for TN and 88.5 % for T-P in rice straw mat with gypsum and PAM plot. This research revealed that rice straw mat cover with soil amendments on the soil surface could not only increase the crop yield but also reduce the NPS pollution loads substantially.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.114-114
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• 2017

하천의 유사량 자료는 하상변동 예측, 저수지 퇴사량 추정, 유사조절 계획 수립 등 유역과 하천관리 그리고 하천 시설물 관리를 위해 필요하다. 최근 4대강 사업구간에 대한 담수용 보로 유입되는 유사량과 하천 유사의 종횡단적 분포와 하상변동량 등의 산정에 기초자료로 활용하고자 유사량 관측망이 구축되어 있다. 본 연구에서는 하천 유사량에 영향을 미치는 유역특성인자에 대한 군집분석을 통해 유사 발생 유역을 분류하고자 한다. 체계화된 유량 및 유사량 측정 방법에 의해 신뢰할만한 유량-총유사량 관계식을 갖는 유량조사사업단의 35개 유역을 대상으로 한다. 유역 군집분석을 수행하고자 유역과 하천에 대한 지형인자, 토양인자, 토지이용 등의 유역특성 매개변수 자료를 수집하였고, 매개변수별 유사도거리 산정에 오류를 줄이기 위해 매개변수를 무차원화 하였다. 유역의 비유사량은 유역면적, 유역경사, 토성, 토지이용 등에 영향을 받았다. K-means 기법에 의해 군집분석을 수행한 결과 유사량 측정 유역은 A, B, C, D 4개의 그룹으로 분류되었다. B그룹 유역은 첨두홍수량이 크고 발생시간이 짧은 유역 및 하천 조건을 가지고 있었으며, 직접유출이 증가하는 지표조건과 침식이 활발한 토양조건을 갖는 것으로 파악되었다. 그룹별로 실측 비유사량을 검토한 결과 B그룹에 포함된 유역의 유사량이 다른 유역에 비해 상대적으로 크게 발생하였다. 이러한 결과는 유역특성 매개변수의 군집분석을 통한 유역의 군집분류가 유역과 하천의 유사관리 측면에서 유용한 관리방안으로 활용될 수 있음을 의미한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.200-200
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• 2017

강우에 의한 토양 침식 및 토사유츨량은 하천 및 유역환경관리 관점에서 가장 중요한 인자 중 하나로 보고되고 있으며, 다양한 분야에서 이에 대한 연구를 수행 중에 있다. 일반적으로 유역에서 발생한 토양침식 및 물의 이동에 의한 토사유출량을 해석하기 위해 SWAT 등과 같은 많은 모형이 적용되고 있지만, 대부분 농업지역에서 이용하는 수평형태의 수문학적 개념에 따른 overland flow 개념을 이용하고 있다. 하지만, 우리나라는 약 70% 이상이 산림으로 이루어진 지역으로 유역환경 해석에 있어 수평적인 개념과 함께 사면내에서 lateral flow와 같은 지표하 흐름의 이동에 관한 개념 역시 필요하지만, 이의 영향에 대한 관련 연구는 부족하다. 최근 수문학의 발달과 더불어 수평적인 개념을 탈피한 사면수문학 개념이 전 세계적으로 발달하고 있으며, 많은 발전을 이루고 있다. 이를 통해 GIS를 기반으로 물리학기반의 GeoWEPP 모형이 미국을 중심으로 개발되었고, 이에 대한 많은 적용 및 평가가 이루어지고 있다. 본 연구에서는 전 세계적으로 평가받고 있는 process 기반의 SWAT 모형과 사면수문학 개념을 반영한 물리학기반의 GeoWEPP 모형을 이용하였다. 이 두 모형은 강우, 지형, 토양도, 토지피 복도 등 두 모형의 입력자료 역시 거의 동일하게 구성되어 있으며, 같은 FORTRAN CODE 및 ArcGIS에서 운영될 수 있도록 이루어져 있어 비교 분석하기 원활하다. 모형의 적용은 매년 심각한 조류가 발생하는 대청호 지류인 소옥천 유역내 중하류에 위치한 옥각교에서 관측된 모니터링 자료(토사유출량과 유출량)를 이용하여 모형의 정확성을 평가 후, 사면수문학 개념의 적용성에 대해 논하였다. 각각의 모형의 결과에 대한 정확성 평가는, Nash-Sutcliffee를 이용하여 실시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.172-172
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• 2020

In recent years, soil erosion has come to be regarded as an essential environmental problem in human life. Soil erosion causes various on- and off-site problems such as ecosystem destruction, decreased agricultural productivity, increased riverbed deposition, and deterioration of water quality in streams. To solve these problems caused by soil erosion, it is necessary to quantify where, when, how much soil erosion occurs. Empirical erosion models such as the Universal Soil Loss Equation (USLE) family models have been widely used to make spatially distributed soil erosion vulnerability maps. Even if the models detect vulnerable sites relatively well by utilizing big data related to climate, geography, geology, land use, etc. within study domains, they do not adequately describe the physical process of soil erosion on the ground surface caused by rainfall or overland flow. In other words, such models remain powerful tools to distinguish erosion-prone areas at the macro scale but physics-based models are necessary to better analyze soil erosion and deposition and eroded particle transport. In this study, the physics-based Surface Soil Erosion Model (SSEM) was upgraded based on field survey information to produce sediment yield at the watershed scale. The modified model (hereafter MoSE) adopted new algorithms on rainfall kinematic energy and surface flow transport capacity to simulate soil erosion more reliably. For model validation, we applied the model to the Doam dam watershed in Gangwon-do and compared the simulation results with the USLE outputs. The results showed that the revised physics-based soil erosion model provided more improved and reliable simulation results than the USLE in terms of the spatial distribution of soil erosion and deposition.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1994.07a
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• pp.184-215
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• 1994

The Hydrogeologic data of 455 water wells comprising geologic and aquifer test were analyzed to determine hydrogeoloic characteristics of Cheju island. The groundwater of Cheju island is occurred in unconsolidated pyroclastic deposits interbedded in highly jointed basaltic and andesic rocks as high level, basal and parabasal types order unconfined condition. The average transmissivity and specific yield of the aquifer are at about 29,300m$^2$/day and 0.12 respectively. The total storage of groundwater is estimated about 44 billion cubic meters(m$^3$). Average annual precipitation is about 3390 million m$^3$ among which average recharge amount is estimated 1494 million m$^3$ equivalent 44.1% of annual precipitation with 638 million m$^3$ of runoff and 1256 million m$^3$ of evapotranspiration. Based on groundwater budget analysis, the sustainable yield is about 620 million m$^3$(41% of annual recharge)and rest of it is discharging into the sea. The geologic logs of recently drilled thermal water wens indicate that very low-permeable marine sediments(Sehwa-ri formation) composed of loosely cemented sandy sat derived from mainly volcanic ashes, at the 1st stage volcanic activity of the area was situated at the 120$\pm$68m below sea level. And also the other low-permeable sedimentary rock called Segipo-formation which is deemed younger than former marine sediment is occured at the area covering north-west and western part of Cheju at the $\pm$70m below sea level. If these impermeable beds are distributed as a basal formation of fresh water zone of Cheju, most of groundwater in Cheju will be para-basal type. These formations will be one of the most important hydrogeologic boundary and groundwater occurences in the area.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.362-371
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• 1996

This study was conducted to investigate the biochemical properties of isolated bacteria, low temperature tolerant methanogens which were selected for use as inoculum for anaerobic fermentation of agricultural and livestock wasted at low temperature. The results, obtained were summarized as follows: Low temperature tolerant methanogens were isolated from the samples which showed the high methanogenesis rate by enrichment culture at low temperature in methanol medium. These methanogens, Methanobacterium M-251 and Methanobacterium M-253 were isolated from swampy sediment at latitude $56.9^{\circ}$, Methanosarcina mazei M-372 from lake sediment IV at latitude $55.0^{\circ}$ N, and Methanobacterium formicicum M-375 from tidal land soil at latitude $37.0^{\circ}N$, respectively. The isolated anaerobic bacteria could not use sugars as carbon sources. The optimum pH value for the growth of M-251 and M-375 was 6.8, but those for M-253 and M-372 6.5 and 7.0, respectively. The minimum growth temperature of isolated, M-251 and M-253 were $8^{\circ}C$ and the optimum temperature $30^{\circ}C$, while the minimum of M-392 and M-395 were $13^{\circ}C$ and the optimum $37^{\circ}C$. The growth rate of isolates at $17.5^{\circ}C$ were lower by 32-50% than that of $30^{\circ}C$. The isolated Methanobacterium strains such as M-251, M-253, and M-375 have lower cell yield, 0.38-1.21g/1M $CH_4$ than 1.14-1.51g/1M $CH_4$ of Methanosarcina mazei M-372.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.1
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• pp.31-36
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• 1981

This pot experiment was conducted to find out the optimal fertilization ratio of the anions (N : S : P) in various soil conditions. Soil samples were collected from uncultivated mountains and hills where development for grasslands is under consideration. The optimum ratios were computed by the $Hom{\grave{e}}s$ systematic variation technique. The results were summarized as follows : 1. The optimum fertilization ratios of the anions (N : S : P) for the high yields of grass - clover mixed sward at various areas were obtained (Table 5). 2. The grass yields in mixed sward were increased by the increase of specific soil characteristics, CEC, OM, T-N, avail-$P_2O_5$. However. it was not recognizable by the contents of the cations, the base saturation, and the pH. 3. The relatively high yields of clover were positively related to the Ca and Mg contents in soils, and it was a factor of the increased total yields of mixed sward. 4. The relatively high optimum fertilization ratios of S in volcanic ash soil in the Cheju district and P in sediment lithosol in Daegu should be taken into account in determing the fertilization rate for high yield of clover in mixed sward.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.965-974
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• 2013

Multiple debris flows occurred on July 27, 2012 in Mt. Umyeon, which resulted in 16 casualties and severe property demage. Accurate reproducing of the propagation and deposition of debris flow is essential for mitigating these disasters. Through applying FLO-2D model to these debris flows and comparing the results with field observations, we seek to evaluate the performance of the model and to analyse the rheological model parameters. Representative yield stress and dynamic viscosity back-calculated for the debris flows in the northern side of Mt. Umyeon are 1022 Pa and 652 $Pa{\cdot}s$, respectively. Numerical results obtained using these parameters reveal that deposition areas of debris flows in Raemian and Shindong-A regions are well reproduced in 63-85% agreement with the field observations. However, the propagation velocities of the flows are significantly underestimated, which is attributable to the inherent limitations of the model that can't take the entrainment of bed material and surface water into account. The debris flow deposition computed in Hyeongchon region where the entrainment is not significant appears to be in very good agreement with the field observation. The sensitivity study of the numerical results on model parameters shows that both sediment volume concentration and roughness coefficient significantly affect the flow thickness and velocity, which underscores the importance of careful selection of these model parameters in FLO-2D modeling.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.897-913
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• 2004

There has been continuous efforts to manage the water resources for the required water quality criterion at river channel in Korea. However, we could not obtain the partial improvement only for the point source pollutant such as, wastewater from urban and industrial site through the water quality management. Therefore, it is strongly needed that the Best Management Practice(BMP) throughout the river basin for water quality management including non-point source pollutant loads. This problem should be resolved by recognizing the non-point source pollutant loads from upstream river basin to the outlet depends on the land use and soil type characteristic of the river basin using the computer simulation by distributed parameter model based on the detailed investigation and the application of Geographic Information System(GIS). Used in this study, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) model is a tool suitable for long term evaluation of the effects of BMPs and can be used for un gauged watershed simulation of runoff and sediment yield. Now applications of model are in progress. So we just describe the limited result. However If well have done modeling and have investigated of propriety of model, well achieve our final goal of this study.