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81.
Dong Jiing Doong Shen Hsien Chen Chia Chuen Kao Beng Chun Lee Sun Pei Yeh 《Ocean Engineering》2007,34(2):234-246
Field oceanographic and meteorological data are required for ocean engineering. In response to the requirement of field data, an operational coastal ocean monitoring network was established around Taiwan coast, including nine deep-water data buoys, one shallow-water pile station, 10 coastal weather stations and 10 tide stations. Data quality check procedures are necessary to ensure the accuracy of measurements. This paper presents the data quality check procedures on ocean wave data which includes automatic and manual check procedures. The checking criteria are derived using statistical theory in this paper. In addition, a sea-state-dependent algorithm is presented in this study in order to derive checking criteria of time-continuity check. It is showed to have better performance of picking up suspicious data than using fixed threshold process. This data quality check program is now used on the operational monitoring network. 相似文献
82.
Zhixue Zhao Xiaoguang Wang Yonghong Hao Tongke Wang Abderrahim Jardani Herve Jourde Tian‐Chyi Jim Yeh Ming Zhang 《水文研究》2019,33(19):2551-2560
The study on the hydraulic properties of coastal aquifers has significant implications both in hydrological sciences and environmental engineering. Although many analytical solutions are available, most of them are based on the same basic assumption that assumes aquifers extend landward semi‐infinitely, which does not necessarily reflect the reality. In this study, the general solutions for a leaky confined coastal aquifer have been developed that consider both finitely landward constant‐head and no‐flow boundaries. The newly developed solutions were then used to examine theoretically the joint effects of leakage and aquifer length on hydraulic head fluctuations within the leaky confined aquifer, and the validity of using the simplified solution, which assumes the aquifer is semi‐infinite. The results illustrated that the use of the simplified solution may cause significant errors, depending on joint effects of leakage and aquifer length. A dimensionless characteristic parameter was then proposed as an index for judging the applicability of the simplified solution. In addition, practical application of the general solution for the constant‐head inland boundary was used to characterize the hydraulic properties of a leaky confined aquifer using the data collected from a field site at the Seine River estuary, France, and the versatility of the general solution was further justified. 相似文献
83.
Identifying the key factors controlling groundwater chemical evolution in mountain-plain transitional areas is crucial for the security of groundwater resources in both headwater basins and downstream plains. In this study, multivariate statistical techniques and geochemical modelling were used to analyse the groundwater chemical data from a typical headwater basin of the North China Plain. Groundwater samples were divided into three groups, which evolved from Group A with low mineralized Ca-HCO3 water, through Group B with moderate mineralized Ca-SO4-HCO3 water, to Group C with highly saline Ca-SO4 and Ca-Cl water. Water-rock interaction and nitrate contamination were mainly responsible for the variation in groundwater chemistry. Groundwater chemical compositions in Group A were mainly influenced by dissolution of carbonates and cation exchange, and suffered less nitrate contamination, closely relating to their locations in woodland and grassland with less pronounced human interference. Chemical evolution of groundwater in Groups B and C was gradually predominated by the dissolution of evaporites, reverse ion exchange, and anthropogenic factors. Additionally, the results of the inverse geochemical model showed that dedolomitization caused by gypsum dissolution, played a key role in the geochemical evolution from Group A to Group B. Heavy nitrate enrichment in most groundwater samples of Groups B and C was closely associated with the land-use patterns of farmland and residential areas. Apart from the high loads of chemical fertilizers in irrigation return flow as the main source for nitrate contamination, the stagnant zones, flood irrigation pattern, mine drainage, and groundwater-exploitation reduction program were also important contributors for such high mineralization and heavy NO3− contents in Group C. The important findings of this work not only provide the conceptual framework for the headwater basin but also have important implications for sustainable management of groundwater resources in other headwater basins of the North China Plain. 相似文献
84.
85.
Two coupled general circulation models, i.e., the Meteorological Research Institute (MRI) and Geophysical Fluid Dynamics Laboratory (GFDL) models, were chosen to examine changes in mixed layer depth (MLD) in the equatorial tropical Pacific and its relationship with ENSO under climate change projections. The control experiment used pre-industrial greenhouse gas concentrations whereas the 2 × CO2 experiment used doubled CO2 levels. In the control experiment, the MLD simulated in the MRI model was shallower than that in the GFDL model. This resulted in the tropical Pacific’s mean sea surface temperature (SST) increasing at different rates under global warming in the two models. The deeper the mean MLD simulated in the control simulation, the lesser the warming rate of the mean SST simulated in the 2 × CO2 experiment. This demonstrates that the MLD is a key parameter for regulating the response of tropical mean SST to global warming. In particular, in the MRI model, increased stratification associated with global warming amplified wind-driven advection within the mixed layer, leading to greater ENSO variability. On the other hand, in the GFDL model, wind-driven currents were weak, which resulted in mixed-layer dynamics being less sensitive to global warming. The relationship between MLD and ENSO was also examined. Results indicated that the non-linearity between the MLD and ENSO is enhanced from the control run to the 2 × CO2 run in the MRI model, in contrast, the linear relationship between the MLD index and ENSO is unchanged despite an increase in CO2 concentrations in the GFDL model. 相似文献
86.
87.
Gour-Tsyh Yeh Yilin Fang Fan Zhang Jiangtao Sun Yuan Li Ming-Hsu Li Malcolm D. Siegel 《Computational Geosciences》2010,14(1):149-170
Subsurface contamination problems of metals and radionuclides are ubiquitous. Metals and radionuclides may exist in the solute
phase or may be bound to soil particles and interstitial portions of the geologic matrix. Accurate tools to reliably predict
the migration and transformation of these metals and radionuclides in the subsurface environment enhance the ability of environmental
scientists, engineers, and decision makers to analyze their impact and to evaluate the efficacy of alternative remediation
techniques prior to incurring expense in the field. A mechanistic-based numerical model could provide such a tool. This paper
communicates the development and verification of a mechanistically coupled fluid-flow thermal-reactive biogeochemical-transport
model where both fast and slow reactions occur in porous and fractured media. Theoretical bases, numerical implementations,
and numerical experiments using the model are described. A definition of the “rates” of fast/equilibrium reactions is presented
to come up with a consistent set of governing equations. Two example problems are presented. The first one is a reactive transport
problem which elucidates the non-isothermal effects on heterogeneous reactions. It also demonstrates that the rates of fast/equilibrium
reactions are not necessarily greater than that of slow/kinetic reactions in the context of reactive transport. The second
example focuses on a complicated but realistic advective–dispersive–reactive transport problem. This example exemplifies the
need for innovative numerical algorithms to solve problems involving stiff geochemical reactions. It also demonstrates that
rates of all fast/equilibrium reactions are finite and definite. Furthermore, it is noted that a species-versus-time curve
cannot be used to characterize the rate of homogeneous fast/equilibrium reaction in a reactive transport system even if one
and only one such reaction is responsible for the production of this species. 相似文献
88.
89.
The effect of the variation of river water levels on the estimation of groundwater recharge in the Hsinhuwei River,Taiwan 总被引:1,自引:1,他引:0
Jung-Wei Chen Hsun-Huang Hsieh Hsin-Fu Yeh Cheng-Haw Lee 《Environmental Earth Sciences》2010,59(6):1297-1307
Land subsidence is a serious problem in Taiwan’s Yunlin area due to groundwater overpumping. There are safety risks in the
high-speed railway structures in the areas of Siluo, Huwei, Tuku, and Yuanchang towns that run from north to south in the
Yunlin area. Therefore, it is important to increase the groundwater recharge and to remedy the land subsidence in this area.
The purpose of this study is to use the stream-flow estimation model (SF) and the groundwater flow numerical software MODFLOW
(MF) to estimate the stream infiltration with consideration to the variation of the river water level in the Hsinhuwei River.
The Ferris analytical model (FA) and MF are used to estimate the increased stream infiltration after the water level of the
river rises. The hydraulic parameters required for each model are obtained from field observations and laboratory experiments.
The results indicate that the assessment of the stream infiltration obtained through the SF and MF models are 264.2 × 104 and 170.9 × 104 m3/year, respectively. When the river water level increases by about 2.5 m, the annual stream infiltration obtained through
the FA and MF models significantly increases by 31.6 × 104 and 26.4 × 104 m3/year, respectively. Taken together, the stream storages estimated using these two models indicate that an increasing efficiency
of groundwater recharge is within the range of 10.0–18.5%. 相似文献
90.
Many civil infrastructures are located near the confluence of two streams, where they may be subject to inundation by high flows from either stream or both. These infrastructures, such as highway bridges, are designed to meet specified performance objectives for floods of a specified return period (e.g. the 100 year flood). Because the flooding of structures on one stream can be affected by high flows on the other stream, it is important to know the relationship between the coincident exceedence probabilities on the confluent stream pair in many hydrological engineering practices. Currently, the National Flood Frequency Program (NFF), which was developed by the US Geological Survey (USGS) and based on regional analysis, is probably the most popular model for ungauged site flood estimation and could be employed to estimate flood probabilities at the confluence points. The need for improved infrastructure design at such sites has motivated a renewed interest in the development of more rigorous joint probability distributions of the coincident flows. To accomplish this, a practical procedure is needed to determine the crucial bivariate distributions of design flows at stream confluences. In the past, the copula method provided a way to construct multivariate distribution functions. This paper aims to develop the Copula‐based Flood Frequency (COFF) method at the confluence points with any type of marginal distributions via the use of Archimedean copulas and dependent parameters. The practical implementation was assessed and tested against the standard NFF approach by a case study in Iowa's Des Moines River. Monte Carlo simulations proved the success of the generalized copula‐based joint distribution algorithm. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献