Wavelet analysis of soil moisture measurements for hillslope hydrological processes

Lee, Eunhyung,Kim, Sanghyun Elsevier 2019 Journal of hydrology Vol.575 No.-

<P><B>Abstract</B></P> <P>Spatial and temporal distributions of soil moisture are important for explaining hydrological processes at the hillslope scale. The fate of various hillslope flow paths can vary seasonally and their relationship with rainfall events can be nonstationary. We collected high resolution in situ soil moisture datasets at 30 points (10 locations in three depths) between March and November in a steep mountainous hillslope. The wavelet coherence analysis of eco-hydrometeorological factors and soil moistures indicated distinctive controls of rainfall and evapotranspiration over soil moisture at time scales of under a day. The vertical flow in upslope areas can be explained by significant wavelet coherence in soil moisture profiles. The appearance of lateral flow with vertical flow in the downslope is associated with even more significant wavelet coherence between identical depths. The wavelet coherence analysis between two soil moisture time series both along hillslope layers and depth profiles provided good spatial and temporal representations of hillslope hydrological processes in terms of their timing and scale. The distributions of soil moisture coherences showed distinctive characteristics for three different seasons. The seasonally distinctive role of vegetation to infiltration was apparent for the upslope area, but the combined impact of vegetation and topography controlled more complicated hydrological processes in the downslope area. The phase angle analysis was introduced to show the profile difference of hydrological processes on various time scales.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrological processes were explored through soil moisture wavelet analysis. </LI> <LI> Vegetation and topography controlled hydrological processes in the downslope area. </LI> <LI> Soil moisture coherence indicates distinct controls and seasonality upslope and downslope. </LI> </UL> </P>

Uncertainty assessment of future projections on water resources according to climate downscaling and hydrological models

Lee, Moon-Hwan,Bae, Deg-Hyo IWA Publishing 2018 Journal of hydroinformatics Vol.20 No.3

<P>Quantifying the uncertainty of future projection is important to assess the reliable climate change impact. In this sense, this study is aimed at investigating the uncertainty sources of various water variables (seasonal dam inflow, 1-day maximum dam inflow, and 30-day minimum dam inflow) according to downscaling methods and hydrological modeling. Five regional climate models (RCMs), five statistical post-processing methods and two hydrological models were applied for the uncertainty analysis. The changes for seasonal dam inflow are 0.1, 58.8, 5.1, and 1.1 mm for the SWAT model and 2.1, 76.1, −8.5, and −2.9 mm for the VIC model in spring, summer, autumn, and winter, respectively. The effects of the hydrological model is smaller than that of RCM for future projections of the seasonal dam inflow. The changes of annual 1-day maximum dam inflow vary according to the selection of RCM whereas the changes of annual 30-day minimum dam inflow are sensitive to the selection of hydrological model. The RCM is the dominant source of uncertainty of all seasonal dam inflow (except for winter) and high flow, whereas the hydrological model is the dominant source of uncertainty in winter dam inflow and low flow. Considering these results, the appropriate multi-model ensemble chain according to target variable will be necessary for reliable climate change impact assessment.</P>

GIS와 ASI 알고리듬을 이용한 광미댐 수문 분석 소프트웨어 개발

최요순,박형동,권현호 한국자원공학회 2011 한국자원공학회지 Vol.48 No.5

This paper presents new software for analyzing the hydrological characteristics of drainage systems around tailings dams. The Adaptive Stormwater Infrastructure(ASI) algorithm, which incorporates a priori information on man-made water-handling structures with a Digital Elevation Model(DEM), was modified to consider effective rainfall for grid-based hydrological analysis. The ArcObjects programing using Visual Basic.NET was carried out to implement the software as an extension toolbar in ArcMap(part of ArcGIS software package). Application of the software to the Sangdong tailings dam revealed that the software can analyze surface runoff patterns during rainfall by considering both surface and underground hydraulic structures. The software is superior to a conventional hydrological analysis tool used in previous studies in terms of providing more reasonable hydrological information on a watershed of tailings dam. It is expected that the software can be effectively utilized to support the design of hydraulic structures in tailings dams. 본 연구에서는 광미댐 인근 지역의 수문 분석을 위해 사용할 수 있는 새로운 소프트웨어를 개발하였다. 수치지형모델과 인공 수리 구조물에 대한 사전 정보를 결합할 수 있는 ASI 알고리듬을 개선하여 격자 기반의 수문 분석시 지역의 유효 유량 자료도 고려할 수 있도록 하였다. 소프트웨어 구현을 위해 Visual Basic.NET을 이용한 ArcObjects 프로그래밍을 수행하였으며, 그 결과 ArcGIS 소프트웨어의 제품군 중 하나인 ArcMap에서 확장 툴바 형태로 소프트웨어를 활용할 수 있었다. 개발된 소프트웨어를 상동광산 신광미댐에 적용한 결과 지형 뿐만 아니라 지상, 지하 배수시설을 함께 고려하여 수문 분석을 수행할 수 있으며, 기존 연구에서 사용되었던 일반적인 수문 분석 도구와 비교할 때 보다 합리적인 분석 결과를 얻을 수 있었다. 본 연구에서 개발한 소프트웨어가 광미댐 배수시설 설계를 지원할 수 있는 도구로서 유용하게 활용될 수 있을 것이라 기대한다.

Singular Spectrum Analysis를 이용한 수문 시계열 예측에 관한 연구

권현한(Kwon Hyun-Han),문영일(Moon Young-Il) 대한토목학회 2006 대한토목학회논문집 B Vol.26 No.2B

본 연구에서는 기존 매개변수적 수문시계열 예측모형을 보완하고자 Singular Spectrum Analysis(SSA)와 Linear Recurrent Formula를 결합한 모형을 제안하였다. SSA는 주로 시계열에 내재해 있는 구성성분을 추출하기 위한 목적으로 많이 이용되고 있다. 이러한 관점에서 본 연구에서는 엘니뇨 및 라니냐 등의 기상현상과 수문사상의 상관성 분석에 주로 적용되고 있는 SSA와 시계열 예측을 위해서 Linear Recurrence Formula를 결합한 예측 모형을 월단위의 수위와 유입량 시계열 자료를 대상으로 적용성 및 타당성을 검토해 보았다. 모형을 통해 수문시계열을 모의한 결과 전체적인 통계적인 특성 및 시각적인 검토에서 실측자료와 매우 유사한 모의가 가능하였으며 실측 자료를 바탕으로 Blind Forecasting을 실시한 결과 2가지 예에서 모두 1년 정도의 예측구간에서 합리적인 결과를 제시하여 주었다. 따라서 단기예측을 수문모형으로서 적용이 가능할 것으로 사료된다. We have investigated the properties of the Singular Spectrum Analysis (SSA) coupled with the Linear Recurrent Formula which made it possible to complement the parametric time series model. The SSA has been applied to extract the underlying properties of the principal component of hydrologic time series, which can often be identified as trends, seasonalities and other oscillatory series, or noise components. Generally, the prediction by the SSA method can be applied to hydrologic time series governed (may be approximately) by the linear recurrent formulae. This study has examined the forecasting ability of the SSA-LRF model. These methods were applied to monthly discharge and water surface level data. These models indicated that two of the time series have good abilities of forecasting, particularly showing promising results during the period of one year. Thus, the method presented in this study suggests a competitive methodology for the forecast of hydrologic time series.

호주 오트웨이 프로젝트 염수층 내 CO₂ 주입에 따른 수리-역학적 연계거동 분석

박정욱(Jung-Wook Park),신영재(Young Jae Shinn),Jonny Rutqvist,천대성(Dae-Sung Cheon),박의섭(Eui-Seob Park) 한국암반공학회 2016 터널과지하공간 Vol.26 No.3

본 연구에서는 TOUGH-FLAC 연동 해석기법을 이용하여 호주 오트웨이 실증프로젝트 염수층 내 이산화탄소 주입을 수치적으로 모델링하고 주변 지층에 야기되는 수리-역학적 거동 특성을 살펴보았다. 대상 부지의 물리검층, 시추코어 분석 및 지구통계기법을 통해 구현된 3차원 추계학적 지질모델을 바탕으로 해석모델을 작성하였으며, 이산화탄소의 주입과 이에 따른 수리-역학적 연계거동을 분석하였다. 총 30,000톤의 이산화탄소를 200일 동안 주입하는 경우, 주입공 주변의 압력 변화는 0.5 MPa 이하로 나타났으며, 주입 5일 경과 시 압력이 수렴하는 경향을 보였다. 지층 내 역학적 거동에는 큰 영향을 미치지 않을 것으로 판단되며, 주변 단층대로의 유동도 미미한 수준으로 나타났다. The present study numerically simulated the CO2 injection into the saline aquifer of CO2CRC Otway pilot project and the resulting hydrological-mechanical coupled process in the storage site by TOUGH-FLAC simulator. A three-dimensional numerical model was generated using the stochastic geological model which was established based on well log and core data. It was estimated that the CO2 injection of 30,000t over a period of 200 days increased the pressure near the injection point by 0.5 MPa at the most. The pressure increased rapidly and tended to approach a certain value at an early stage of the injection. The hydrological and mechanical behavior observed from the CO2 flow, effective stress change and stress-strength ratio revealed that the CO2 injection into the saline aquifer under the given condition would not have significant effects on the mechanical safety of the storage site and the hydrological state around the adjacent fault.

암반공동 열에너지저장소 주변 암반의 열-수리-역학적 연계거동 분석

박정욱(Jung-Wook Park),Jonny Rutqvist,류동우(Dongwoo Ryu),신중호(Joong-Ho Synn),박의섭(Eui-Seob Park) 한국암반공학회 2015 터널과지하공간 Vol.25 No.1

본 연구에서는 TOUGH2-FLAC3D 연계해석기법을 이용하여 암반공동에 고온의 열에너지를 30년간 저장하는 경우 주변 암반에 야기되는 열-수리-역학적 연계거동을 살펴보았다. 열에너지저장에 따른 암반의 거동 특성 및 환경 영향을 예측하고 이에 대한 제어기준을 수립하기 위한 기초 연구로서, 저장소 주변 암반에서 발생하는 열-수리 흐름과 역학적 거동의 상호작용에 대하여 검토하였다. 기본해석으로서 결정질 암반 내 원통형 공동에 350℃의 대용량 열에너지를 저장하는 경우를 모델링하였으며, 열에너지저장소의 단열성능은 고려하지 않았다. 암반 내 열전달의 주요 메카니즘은 암반의 전도에 의한 것으로 판단되며, 암반의 역학적 거동은 수리적 요소보다는 열적 요소에 지배적인 영향을 받는 것으로 나타났다. 암반과 지하수 가열에 따른 유효응력 재분포 양상과 열팽창으로 인한 암반 변위 및 지표 융기를 검토하였으며, 주변 암반에서의 전단파괴 위험도를 정량적인 수치를 통해 제시하였다. 암반 가열에 따른 열팽창으로 인하여 지표면에서 수 cm의 융기가 발생하였으며, 저장공동 상부에 인장응력이 크게 발달하면서 전단파괴의 위험도가 증가하는 것으로 나타났다. The thermal-hydrological-mechanical (T-H-M) behavior of rock mass surrounding a high-temperature cavern thermal energy storage (CTES) operated for a period of 30 years has been investigated by TOUGH2-FLAC3D simulator. As a fundamental study for the development of prediction and control technologies for the environmental change and rock mass behavior associated with CTES, the key concerns were focused on the hydrological-thermal multiphase flow and the consequential mechanical behavior of the surrounding rock mass, where the insulator performance was not taken into account. In the present study, we considered a large-scale cylindrical cavern at shallow depth storing thermal energy of 350℃. The numerical results showed that the dominant heat transfer mechanism was the conduction in rock mass, and the mechanical behavior of rock mass was influenced by thermal factor (heat) more than hydrological factor (pressure). The effective stress redistribution, displacement and surface uplift caused by heating of rock and boiling of ground-water were discussed, and the potential of shear failure was quantitatively examined. Thermal expansion of rock mass led to the ground-surface uplift on the order of a few centimeters and the development of tensile stress above the storage cavern, increasing the potential of shear failure.

산림특성에 따른 강우유출수 유출특성 및 상관관계 분석

정우진 ( Woojin Chung ),장순웅 ( Soonwoong Chang ) 한국환경과학회 2016 한국환경과학회지 Vol.25 No.7

Environmental policy implementation has been strengthened to protect the source waters in Korea and to improve their water quality. Increasing of non-point source caused water quality problem continuously. Research on runoff from forests, which occupy over 65% of the land in korea, is insufficient, and studies on the characteristics and influences of storm runoff are necessary. In this study, we chose to compare the effects of land use in the form of two types of forest distribution and then gathered data on storm characteristics and runoff properties during rainfall events in these areas. Furthermore, the significance and influences of the discharges were analyzed through correlation analysis, and multilateral runoff characteristics were examined by deducing a formula through COD(Mn) and TOC regression analysis. At two forest points, for which the basin areas differed from each other, flow changed according to storm quantity and intensity. The peak discharge at point A, where the basin area was big, was high, whereas water-quality fundamental items (BOD, COD(Mn), and SS) and TOC density were high at point B where the slope and storm intensity were high. Effects of dissolved organic matter were determined through correlation analysis, and the regression formulas for COD(Mn) and TOC were deduced by regression analysis. It is expected that the data from this study could be useful as basic information in establishing forest management measures.

시나리오 중립 접근법을 활용한 기후변화 시나리오에 따른 보령시 가뭄의 수문학적 위험도 평가

김지영,한영만,서승범,김대하,김태웅 한국수자원학회 2024 한국수자원학회논문집 Vol.57 No.3

기후위기에 선제적으로 대비하기 위해서는 기후변화에 따른 영향을 예측 및 분석하고, 이를 바탕으로 기후위기 적응과 관련한 정책과 전략을 수립할 필요가 있다. 이를 위해 기후변화를 고려해야 하나, 기존 연구 방법인 시나리오 리드 접근법에서 연구자들은 기후변화 대표 시나리오를 선택하여 활용하기 때문에, 예측된 결과의 불확실성이 크고 신뢰도가 낮다. 이러한 연구 결과는 기후변화 관련된 수자원 정책 및 설계기준에 반영되는 데 한계가 있다. 따라서 기후변화로 인해 발생가능한 변화 범위를 고려하는 시나리오 중립 접근법을 활용할 필요가 있다. 본 연구에서는 보령시를 대상으로 총 343개의 기후스트레스 시계열을 생성한 뒤 이변량 가뭄빈도분석을 통해 재현기간을 산정하고 가뭄에 대한 수문학적 위험도를 산정하였다. 분석결과, SSP1-2.6 18개 및 SSP5-8.5에 18개에 대해 최대 재현기간의 가뭄이 20년 내에 발생할 수문학적 위험도는 0.15±0.025, 50년 내에 발생할 수문학적 위험도는 0.3125±0.0625 사이로 나타났다. 따라서 보령시에서는 해당 범위의 수문학적 위험도를 고려하여 가뭄 정책 및 대책 수립이 필요하다. To prepare for the impending climate crisis, it is necessary to establish policies and strategies based on scientific predictions and analyses of climate change impacts. For this, climate change should be considered, however, in conventional scenario-led approach, researchers select and utilize representative climate change scenarios. Using the representative climate change scenarios makes prediction results high uncertain and low reliable, which leads to have limitations in applying them to relevant policies and design standards. Therefore, it is necessary to utilize scenario-neutral approach considering possible change ranges due to climate change. In this study, hydrologic risk was estimated for Boryeong after generating 343 time series of climate stress and calculating drought return period from bivariate drought frequency analysis. Considering 18 scenarios of SSP1-2.6 and 18 scenarios of SSP5-8.5, the results indicated that the hydrologic risks of drought occurrence with maximum return period ranged 0.15±0.025 within 20 years and 0.3125±0.0625 within 50 years, respectively. Therefore, it is necessary to establish drought policies and countermeasures in consideration of the corresponding hydrologic risks in Boryeong.

연구논문 : 산지습지의 수문지형분석 방법론의 개발

장은세 ( Eun Se Jang ),이은형 ( Eun Hyung Lee ),김상현 ( Sang Hyun Kim ) 한국환경과학회 2015 한국환경과학회지 Vol.24 No.11

In this study, a digital terrain analysis had been performed for a mountainous watershed having wetlands. In order to consider the impact for wetland in the flow determination algorithm, the Laplace equation is implemented into the upslope accounting algorithm of wetness computation scheme. The computational algorithm of wetland to spatial contribution of downslope area and wetness was also developed to evaluate spatially distributed runoff due to the presence of wetland. Developed schemes were applied to Wangpichun watershed located Chuncuk mountain at Ulzingun, South Korea. Both spatial distribution of wetness and its histogram indicate that the developed scheme provides feasible consideration of wetland impact in spatial hydrologic analysis. The impact of wetland to downslope propagation pattern is also useful to evaluate spatially distributed runoff distribution.

초기 변동수위를 고려한 제방 월류에 따른 안정성 분석

김진영,김재홍,김태헌,김유성 한국지반공학회 2015 한국지반공학회논문집 Vol.31 No.8

It is not possible to provide resonable evidence for embankment (or dam) overtopping in geotechnical engineering, and conventional analysis by hydrologic design has not provided the evidence for the overflow. However, hydrologic design analysis using Copula function demonstrates the possibility that dam overflow occurs when estimating rainfall probability with rainfall data for 40 years based on fluctuating water level of a dam. Hydrologic dam risk analysis depends on complex hydrologic analyses in that probabilistic relationship needs to be established to quantify various uncertainties associated with modeling process and inputs. The systematic approaches to uncertainty analysis for hydrologic risk analysis have not been addressed yet. In this paper, the initial level of a dam for stability of a dam is generally determined by normal pool level or limiting the level of the flood, but overflow of probability and instability of a dam depend on the sensitivity analysis of the initial level of a dam. In order to estimate the initial level, Copula function and HEC-5 rainfall-runoff model are used to estimate posterior distributions of the model parameters. For geotechnical engineering, slope stability analysis was performed to investigate the difference between rapid drawdown and overtopping of a dam. As a result, the slope instability in overtopping of a dam was more dangerous than that of rapid drawdown condition.