Contribution of baseflow during dry spells in irregular channel cross section          下载免费PDF全文

Tae Beom Kim  Jeong‐Seok Yang 《水文研究》2017,31(5):1161-1173

The discharge and water level of a gaining stream are known to be maintained during dry spells by baseflow, which is defined as discharge from underground storage. However, the effect of baseflow on a real river is not well known because direct measurements of baseflow in field are difficult to conduct. Therefore, this study attempts to clarify the contribution of baseflow to streamflow and the extent to which the water level is maintained even during dry spells. A digital filter technique is applied to the records of daily mean streamflow in order to estimate the amount of baseflow, and the lateral distribution method is applied to irregular cross sections at observational sites to obtain the stage–discharge rate curve. Through a comparison of the observed data and calculation results, the amount of baseflow is estimated across the channel, in addition to the maximum water level retained during dry spells in relation to the baseflow. Finally, based on the results of an energy conservation model, this study proposes that the source of the amount of baseflow estimated across a channel section may be different from that of the water level maintained during dry spells.  相似文献   

The Heuksan mud belt on the tide-dominated shelf of Korea: a supply-driven depositional system?     

Tae Soo Chang  Hun Jun Ha 《Geo-Marine Letters》2015,35(6):447-460

  相似文献   

Influence of evaporation from the forest floor on evapotranspiration from the dry canopy     

Kenichi Daikoku  Shigeaki Hattori  Aiko Deguchi  Yu Aoki  Mari Miyashita  Kazuho Matsumoto  Junichi Akiyama  Shinichi Iida  Tae Toba  Yuji Fujita  Takeshi Ohta 《水文研究》2008,22(20):4083-4096

  相似文献   

Groundwater responses to the 2011 Tohoku Earthquake on Jeju Island,Korea     

Soo‐Hyoung Lee  Kyoochul Ha  Se‐Yeong Hamm  Kyung‐Seok Ko 《水文研究》2013,27(8):1147-1157

Groundwater responses at 15 monitoring wells on Jeju Island were observed in relation to the magnitude 9.0 Tohoku Earthquake off the Pacific coast of Honshu, Japan, on 11 March 2011, at 14:46:23 h local time (05:46:24 h UTC time). In coastal areas, the groundwater level responses to the earthquake were oscillatory at 12 wells, and the range of the maximum groundwater level changes was 3–192.4 cm. The response durations were approximately 1–62 min. The relationship between the maximum groundwater level changes and the response durations displayed a high correlation coefficient (r = 0.81). Groundwater temperature changes were also observed at 7 of 12 wells 3–10 min after the seismic wave arrived, and the range was from 0.01 °C to 1.20 °C. In mid‐elevation areas, the groundwater level changes appeared in three different forms: oscillatory, spiky and persistent. The groundwater temperature changes were also observed at two wells. One indicated decreasing and recovering temperatures, and the other exhibited rising and persistent temperatures. The primary temperature changes occurred 5–6 min after the earthquake and 2–3 min after the seismic wave arrived. In addition, the electrical conductivities at the depth of the transition zone were monitored, and the responses to the earthquake appeared at all three wells. Although the electrical conductivity and temperature changes were not well understood, groundwater inflow and mixing were likely caused by the earthquake, and the responses were various and site specific. The responses to the earthquake were closely related to the hydrogeological characteristics at each monitoring well, and a more detailed hydrogeological characterization is needed to understand the mechanisms related to earthquakes in general. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Construction of design hyetographs for locations without observed data     

Gwo‐Fong Lin  Ming‐Chang Wu  Guo‐Rong Chen  Shen‐Jung Liu 《水文研究》2010,24(4):481-491

A design hyetograph which represents the time distribution of design rainfall depth corresponding to a duration and a return period is essential in hydrologic design. However, for locations without observed data (ungauged sites), construction of design hyetographs is a difficult task because of the lack of data. Hence, an approach based on self‐organizing map (SOM) is proposed in this paper to construct design hyetographs at ungauged sites. SOM, which is a special kind of artificial neural networks (ANNs), is a powerful technique for extracting and visualizing salient features of data and for solving classification problems. The proposed approach is composed of three steps: classification, assignment and construction. First, the SOM‐based classification is performed to analyse gauged sites' design hyetographs. Second, based on the concept of indicator kriging, a method is developed to assign an ungauged site of interest to a certain cluster. Third, based on the spatial information, the clustering results, and the design hyetographs of gauged sites, the design hyetograph at the site of interest is constructed using the reciprocal‐distance‐squared method. An application is conducted to assess the advantages of the proposed approach over the conventional approaches. Moreover, cross‐validation tests are applied to evaluate the performance of the accuracy and the robustness of the proposed approach. The results confirm the improvement in performance by using the proposed approach instead of conventional approaches. The proposed approach is useful for constructing design hyetographs at ungauged sites. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Estimation of mean water transit time on a steep hillslope in South Korea using soil moisture measurements and deuterium excess          下载免费PDF全文

Sanghyun Kim  Sungwon Jung 《水文研究》2014,28(4):1844-1857

A method for estimating daily mean transit time (DMTT) within a soil layer was proposed using field measurements of soil moisture. Vertical profiles of soil moisture time series were used for storage estimation. Water fluxes were evaluated through matrix and bypass flow. Variations in soil moisture and soil thickness were used to evaluate matrix flow. Exponential decay in depth of macropores was also used for bypass flow approximation. DMTT evaluation was compared to results obtained from a stable water isotope model using two years of data acquired on a steep granite hillslope in the Sulmachun watershed, South Korea. Various uncertainties in transit time evaluation such as model structure, non‐stationary assumption and data acquisition of existing approaches can be accounted for in the proposed methodology, and the flowpath contribution can be further configured in conjunction with hydrometric measurements. Probability density functions of isotope analyses were partially explained by transit time distributions that were based on soil moisture measurements. Supplementary sensitivity analyses for uncertainty configurations indicate that matrix flow is the primary process in determining transit time distribution while the impact of bypass flow is minor. The feasibility of a DMTT approach over isotope‐based methodologies highlights not only the strength of this proposed method, both in cost and time, but also its further application potential for existing soil moisture measurements. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Assessment of the impact of climate change on the flow regime of the Han River basin using indicators of hydrologic alteration     

Byung‐Sik Kim  Bo‐Kyung Kim  Hyun‐Han Kwon 《水文研究》2011,25(5):691-704

Most natural disasters are caused by water‐/climate‐related hazards, such as floods, droughts, typhoons, and landslides. In the last few years, great attention has been paid to climate change, and especially the impact of climate change on water resources and the natural disasters that have been an important issue in many countries. As climate change increases the frequency and intensity of extreme rainfall, the number of water‐related disasters is expected to rise. In this regard, this study intends to analyse the changes in extreme weather events and the associated flow regime in both the past and the future. Given trend analysis, spatially coherent and statistically significant changes in the extreme events of temperature and rainfall were identified. A weather generator based on the non‐stationary Markov chain model was applied to produce a daily climate change scenario for the Han River basin for a period of 2001–2090. The weather generator mainly utilizes the climate change SRES A2 scenario driven by input from the regional climate model. Following this, the SLURP model, which is a semi‐distributed hydrological model, was applied to produce a long‐term daily runoff ensemble series. Finally, the indicator of hydrologic alteration was applied to carry out a quantitative analysis and assessment of the impact of climate change on runoff, the river flow regime, and the aquatic ecosystem. It was found that the runoff is expected to decrease in May and July, while no significant changes occur in June. In comparison with historical evidence, the runoff is expected to increase from August to April. A remarkable increase, which is about 40%, in runoff was identified in September. The amount of the minimum discharge over various durations tended to increase when compared to the present hydrological condition. A detailed comparison for discharge and its associated characteristics was discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Multi‐species diffusion analysis in porous media under various dry density and temperature conditions: molecular dynamics simulation,homogenization analysis,and finite element method     

Jung Hae Choi  Katsuyuki Kawamura  Kazushi Kimoto  Yasuaki Ichikawa  Byung‐Gon Chae 《国际地质力学数值与分析法杂志》2014,38(16):1744-1760

In porous media, chemical species that dissolve in pore water can be transported via diffusion mechanisms or advective fluxes, close to or far away from where precipitation occurs. In the case of a high‐level radioactive waste disposal system, compacted bentonite is used in a buffer material in an engineering barrier system to minimize the amount of specific nuclides that breach into the surrounding host rock. To minimize breaching, it is very important to understand the transport mechanism of multiple chemical species in porous media. In the following research, we introduced FEM analysis methods using the results of the molecular dynamics simulation and homogenization analysis (MD/HA) method. First, the diffusion coefficients of ions (Cl^?, I^?, and Na⁺) in different water layers of Na‐beidellite were calculated using the MD/HA procedure under various dry density (1.2, 1.6, and 2.0 Mg/m³) and temperature (293, 323, and 363 K) conditions. Next, using FEM analysis that used the MD/HA results as input parameters, the diffusion behaviors of ions in porous media were calculated. The results indicate that the diffusion coefficients of the interlayer water in Na‐beidellite are different from the diffusion coefficients under dry density conditions. Further, the concentration profiles (C_t/C₀) of iodine and chloride are proportional to temperature but inversely proportional to dry density. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Holding capacity of suction caisson anchors embedded in cohesive soils based on finite element analysis     

Jaehun Ahn  Hanmin Lee  Yun‐Tae Kim 《国际地质力学数值与分析法杂志》2014,38(15):1541-1555

The foundations of offshore structures have been intensively studied to provide design guidelines for oil platforms. Recently, techniques developed for the oil industry have found new applications in the design of foundations for offshore wind turbines. There are simplified analytical solutions for the holding capacity of suction anchors, which are based on postulated failure mechanisms and are often compared with the results of finite element analyses. The merit of the results of a finite element analysis over the simplified solutions is that the finite element analysis satisfies all the basic equations in mechanics and does not require the assumption of reasonable failure mechanisms. The aim of this study is, based on the results of extensive finite element analyses, to provide a set of formulae for the estimation of the holding capacities of optimally loaded suction caisson anchors embedded in cohesive soils with a linear strength distribution. The bearing capacity factor and the depth of the optimal loading point are also estimated and reported. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Origin of Meso-Proterozoic post-collisional leucogranite suites (Kaokoveld, Namibia): constraints from geochronology and Nd, Sr, Hf, and Pb isotopes     

S. Jung  K. Mezger  O. Nebel  E. Kooijman  J. Berndt  F. Hauff  C. Münker 《Contributions to Mineralogy and Petrology》2012,163(1):1-17

Leucocratic granites of the Proterozoic Kaoko Belt, northern Namibia, now preserved as meta-granites, define a rock suite that is distinct from the surrounding granitoids based on their chemical and isotopic characteristics. Least evolved members of this ~1.5–1.6-Ga-old leucogranite suite can be distinguished from ordinary calc-alkaline granites that occur elsewhere in the Kaoko Belt by higher abundances of Zr, Y, and REE, more radiogenic initial ε_Nd values and unradiogenic initial ⁸⁷Sr/⁸⁶Sr. The leucogranites have high calculated zircon saturation temperatures (mostly > 920°C for least fractionated samples), suggesting that they represent high-temperature melts originating from deep crustal levels. Isotope data (i.e., ε_Ndi: +2.3 to –4.2) demonstrate that the granites formed from different sources and differentiated by a variety of processes including partial melting of mantle-derived meta-igneous rocks followed by crystal fractionation and interaction with older crustal material. Most fractionation-corrected Nd model ages (T_DM) are between 1.7 and 1.8 Ga and only slightly older than the inferred intrusion age of ca. 1.6 Ga, indicating that the precursor rocks must have been dominated by juvenile material. Epsilon Hf values of zircon separated from two granite samples are positive (+11 and +13), and Hf model ages (1.5 and 1.6 Ga) are similar to the U–Pb zircon ages, again supporting the dominance of juvenile material. In contrast, the Hf model ages of the respective whole rock samples are 2.3 and 2.4 Ga, demonstrating the involvement of older material in the generation of the granites. The last major tectonothermal event in the Kaoko Belt in the Proterozoic occurred at ca. 2.0 Ga and led to reworking of mostly 2.6-Ga-old rocks. However, the presence of 1.6 Ga “post-collisional” granites reflects addition of some juvenile mantle-derived material after the last major tectonic event. The results suggest that similar A-type leucogranites are potentially more abundant in crustal terranes but are masked by AFC processes. In the case of the Kaoko Belt, it is suggested that this rock suite indicates a yet unidentified period of mantle-derived crustal growth in the Proterozoic of South Western Africa.  相似文献