Scenarios of the spread of a waste heat discharge in a river — Vistula River case study

The problem of two-dimensional mathematical modelling of heated cooling water discharges into running waters is considered in the paper. Two models — one for the evaluation of 2D turbulent velocity field and the other, developed by authors of the study, for 2D heat transport in open-channels — were used in the calculations. Relevant scenarios of the spread of heated water discharged from a designed gas-stem power plant to be constructed at the Vistula River were presented. Environmentally most friendly variant of the discharge of the thermal pollution was selected from among four various variants.     

Impacts of massive pumping on flood processes in polders—with a case study on Lannihu basin in the Dongting Lake District,China

Flooding risk in polders is dictated by not only rainfall, topography, and land use, but also massive pumping. Unfortunately, existing models are inadequate for resolving floods as water transfer due to pumping is insufficiently accounted for. Here an improved hydrological model (MGB-MP) is proposed under the framework of the large-scale hydrological model (MGB) based on the principle of water balance, explicitly incorporating massive pumping within a polder and also out to external rivers. The proposed model is calibrated and validated for the Lannihu basin, a typical polder with an area of 1353 km² and 126 pumping stations in the Dongting Lake District, China and surrounded by Xiangjiang River and Zishui River. The model performs fairly well, with Nash-Sutcliffe efficiencies concerning water levels over 0.76 for the calibration and over 0.73 for the validation. The model is applied to the Lannihu basin under different pumping station settings and rainfall scenarios to unravel how and to what extent massive pumping affects the flood processes as characterized by water levels and discharge hydrographs. It is shown that massive pumping considerably alters the discharge hydrographs and accordingly leads to substantial decrease in the water levels of rivers, which are independent unit-polders, due to water transfer between unit-polders within the basin and out of the basin. The closer the unit-polders are to pumping stations, the more the water levels in unit-polders decrease. The water levels in unit-polders away from a pumping station is affected by the pumping station capacity to a greater extent than the pumping station's threshold water level for initiating pumping.     

Internal structure and occurrence of accretionary lapilli — a case study at Laacher See Volcano

Accretionary lapilli are common in fine-grained pyroclastic flow and surge deposits and related co-ignimbrite/co-surge ash layers of Laacher See volcano. Two morphologically different types are distin-guished: (1) Rim-type lapilli are composed of a coarse-grained core surrounded by a fine-grained rim. Rims are internally graded or made up of several layers of alternating fine and very-fine grained ash. (2) Core-type lapilli lack fine-grained rims. Field relationships, internal, and grain-size characteristics are specific to accretionary lapilli from different types of tephra deposits. Accretionary lapilli may therefore be a helpful tool to infer the origin of tephra of different origin. In co-ignimbrite ashfall, accretionary lapilli are generally concentrated at the base, whereas pyroclastic flow and surge deposits contain lapilli in the upper parts of individual, thin-bedded layers. Rim-type lapilli are found in pyroclastic flow and surge deposits up to 4 km from the source. Core-type lapilli occur at greater distances or are associated with vesiculated tuffs where they are within 1 km from the vent. Accretionary lapilli from co-ignimbrite/co-surge ash show open framework textures and edge-to-face contacts of individual ash particles. Vesicularity is generally low but the overall porosity of 40% to 50% results in an average density of 1200 kg/m³. Accretionary lapilli in pyroclastic flow and surge deposits are more densely packed and platy particles are often in face-to-face contacts. Vesicularity of those from pyroclastic flow deposits is significantly higher; the overall porosity is about 30% to 40% and the average density 1600 kg/m³. Grain-size analyses show that the accretionary lapilli in co-ignimbrite/co-surge ashfall deposits are the most fine-grained with a median (Md) of 20 to 30 m and a maximum grain size of 250 to 350 m. Accretionary lapilli from pyroclastic flow deposits have intermediate Md-values of 30 to 50 m and a maximum grain size of 350 to 500 m. Those of surge deposits are the coarsest grained with Md-values of 30 to >63 m and a maximum grain size up to 2 mm.     

A case study of the evolution of a Kelvin–Helmholtz wave and turbulence in noctilucent clouds

Bright and extensive noctilucent clouds (NLC) were observed in Århus (Denmark) on 3/4 July of 2008 with an automatic digital camera taking images every minute. This event was unique in the sense that bright NLC were seen at high elevation angles (more than 30°) that allowed observing the evolution of a Kelvin–Helmholtz (KH) wave, resulted in well-developed turbulence. In particular, coherent vortex structures of a horseshoe-shaped form were observed for the first time in noctilucent clouds. The turbulent diffusion coefficient and turbulent energy dissipation rate around the mesopause are estimated in the range 162–667 m²/s and 300–1235 mW/kg, respectively, representing a case of strong neutral air turbulence in noctilucent clouds. Turbulent structures were observed to be in the vicinity of breaking small-scale gravity waves that seems to be responsible for a high level of turbulence.At the same time, it has been demonstrated that it is of importance to take into account non-turbulent process such as the gravity wave motion that is always present in NLC layers. Unless non-turbulent process is taken into account, this certainly leads to overestimating of the value of the turbulent diffusion coefficient. More accurate characteristics of turbulence in NLC can be obtained by analyzing a sequence of high-resolution images with a high frame-rate high-resolution digital camera.     

Impact of climate and land-use changes on hydrological processes and sediment yield—a case study of the Be River catchment,Vietnam

Abstract

The impact of climate and land-use changes on hydrological processes and sediment yield is investigated in the Be River catchment, Vietnam, using the Soil and Water Assessment Tool (SWAT) hydrological model. The sensitivity analysis, model calibration and validation indicated that the SWAT model could reasonably simulate the hydrology and sediment yield in the catchment. From this, the responses of the hydrology and sediment to climate change and land-use changes were considered. The results indicate that deforestation had increased the annual flow (by 1.2%) and sediment load (by 11.3%), and that climate change had also significantly increased the annual streamflow (by 26.3%) and sediment load (by 31.7%). Under the impact of coupled climate and land-use changes, the annual streamflow and sediment load increased by 28.0% and 46.4%, respectively. In general, during the 1978–2000 period, climate change influenced the hydrological processes in the Be River catchment more strongly than the land-use change.

Editor Z.W. Kundzewicz; Associate editor Q. Zhang

Citation Khoi, D.N. and Suetsugi, T., 2014. Impact of climate and land-use changes on hydrological processes and sediment yield—a case study of the Be River catchment, Vietnam. Hydrological Sciences Journal, 59 (5), 1095–1108.     

Spatial-temporal characteristics of epidemic spread in-out flow——Using SARS epidemic in Beijing as a case study

For better detecting the spatial-temporal change mode of individual susceptible-infected-symptomatic-treated-recovered epidemic progress and the characteristics of information/material flow in the epidemic spread network between regions,the epidemic spread mechanism of virus input and output was explored based on individuals and spatial regions.Three typical spatial information parameters including working unit/address,onset location and reporting unit were selected and SARS epidemic spread in-out flow in Beijing was defined based on the SARS epidemiological investigation data in China from 2002 to 2003 while its epidemiological characteristics were discussed.Furthermore,by the methods of spatial-temporal statistical analysis and network characteristic analysis,spatial-temporal high-risk hotspots and network structure characteristics of Beijing outer in-out flow were explored,and spatial autocorrelation/heterogeneity,spatial-temporal evolutive rules and structure characteristics of the spread network of Beijing inner in-out flow were comprehensively analyzed.The results show that(1)The outer input flow of SARS epidemic in Beijing concentrated on Shanxi and Guangdong provinces,but the outer output flow was disperse and mainly includes several north provinces such as Guangdong and Shandong.And the control measurement should focus on the early and interim progress of SARS breakout.(2)The inner output cases had significant positive autocorrelative characteristics in the whole studied region,and the high-risk population was young and middle-aged people with ages from 20 to 60 and occupations of medicine and civilian labourer.(3)The downtown districts were main high-risk hotspots of SARS epidemic in Beijing,the northwest suburban districts/counties were secondary high-risk hotspots,and northeast suburban areas were relatively safe.(4)The district/county nodes in inner spread network showed small-world characteristics and information/material flow had notable heterogeneity.The suburban Tongzhou and Changping districts were the underlying high-risk regions,and several suburban districts such as Shunyi and Huairou were the relatively low-risk safe regions as they carried out minority information/material flow.The exploration and analysis based on epidemic spread in-out flow help better detect and discover the potential spatial-temporal evolutive rules and characteristics of SARS epidemic,and provide a more effective theoretical basis for emergency/control measurements and decision-making.     

Erosion and aggradation on persistently active volcanoes—a case study from Semeru Volcano,Indonesia

Erosion processes on active volcanoes in humid climates result in some of the highest sediment yields on Earth. Episodic sediment yields after large eruptions have been evaluated, but not the long-term and continuous patterns on persistently active volcanoes. We have used high-spatial resolution satellite imagery and DEMs/DSMs along with field-based geologic mapping to assess accurately sediment budgets for the active Semeru Volcano in Java, Indonesia. Patterns of aggradation and degradation on Semeru differ from that of other active volcanoes because (1) both episodic pyroclastic density currents (PDC) and continuous supplies of tephra generate pulses of sediment, (2) sediment is transferred via cycles of aggradation and degradation that continue for >15 years in river channels after each PDC-producing eruption, and (3) rain-triggered lahars remove much greater material than fluvial transport during long, intense rainfall events. The geomorphic response of two of Semeru’s rivers to volcanic sediment migration indicates that (1) each river experiences alternating aggradation and degradation cycles following PDC-producing eruptions and (2) spatial patterns of sediment transfer are governed by geomorphic characteristics of the river reaches. Usually high degradation in the steep source reach is followed by a long bypassing middle reach. Aggradation predominates in the depositional reaches further down valley on the ring plain. Average sediment yields (10³–10⁵ t/km²/year) at persistently active volcanoes are two to three orders of magnitude lower than sediment yields after large and infrequent eruptions, but the continuous and steady sediment transfer in rivers removes more sediment on a mid-term (10 years) to long-term (30 years) basis. In contrast to the trend observed on composite cones after large and infrequent eruptions, decay of sediment yields is not exponential and river channels do not fully recover at steadily active volcanoes as episodic inputs from BAF eruptions, superimposed on the background remobilization of daily tephra, have a greater cumulative effect.     

Flood management and a GIS modelling method to assess flood-hazard areas—a case study

Abstract

This paper presents a viable approach for flood management strategy in a river basin based on the European Floods Directive. A reliable flood management plan has two components: (a) a proper flood management strategy, and (b) the determination of the flood-hazard areas. A method to evaluate the benefits of a flood warning system is presented herein, as well as a method to estimate the flood-hazard areas. Six factors were considered in order to estimate the spatial distribution of the hazardous areas: flow accumulation, slope, land use, rainfall intensity, geology and elevation. The study area was divided into five regions characterized by different degrees of flood hazard ranging from very low to very high. The produced map of flood-hazard areas identifies the areas and settlements at high risk of flooding. The proposed methodology can be applied to any river basin and here was applied to the Koiliaris River basin in Greece.

Citation Kourgialas, N. N. & Karatzas, G. P. (2011) Flood management and a GIS modelling method to assess flood-hazard areas—a case study. Hydrol. Sci. J. 56(2), 212–225.     

Variations in solar radiation in the solar activity cycle: Response of Earth’s atmospheric parameters (numerical modeling and analysis of observational data)

The results of a three-dimensional numerical simulation of changes in the temperature and wind within a height range of up to 100 km caused by changes in fluxes in the solar ultraviolet (UV) radiation in the 23rd solar activity cycle (which was characterized by unusually low values of UV-radiation fluxes) and also of global changes in the ozone content are presented. The simulation results showed that the response of the temperature to variations in the UV radiation are substantially of a nonzonal character, which is caused by the presence in the model of sources of quasi-stationary waves corresponding to the observational data.     

Complexity analysis of precipitation using the Lempel–Ziv algorithm and a multi-scaling approach: a case study in Jilin province,China

Precipitation is an important part of the hydrologic cycle, and its complexity is closely related to surface runoff and changing groundwater dynamics, which in turn influences the accuracy of precipitation forecasts. In this study, we used the Lempel–Ziv algorithm (LZA) and a multi-scaling approach to assess precipitation complexity for 1958–2011 by analyzing time series data from 28 gauging stations located throughout Jilin province, China. The spatial distribution of normalized precipitation complexity was measured by LZA, a symbolic dynamics algorithm, and by a multi-scaling approach, which is described by fractals. In addition, the advantages and limitations of these two methods were investigated. The results indicate that both methods are applicable and consistent for calculating precipitation complexity, and that the degree of relief is a primary factor controlling precipitation complexity in the mountainous area; in the plain terrain, however, the prominent influencing factor is climate.     

Hydrodynamic characteristics of Wujiangdu Reservoir during the dry season—a case study of a canyon reservoir

With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs play a pivotal role in controlling the spatiotemporal distribution of physical and chemical properties of the stored water, hydrodynamic characteristics are of great importance in understanding biogeochemical cycles in those reservoirs. To further this understanding, a field campaign was conducted in the Wujiangdu Reservoir of Guizhou Province. It was found that from the reservoir inlet to the front of the dam, velocity(v) was negativelycorrelated and had a logarithmic relationship with distance along the ship track(s) under dry-season flow conditions[v =-0.104 ln(s) + 0.4756]. Analysis showed that dryseason flow velocity had no significant correlation with water temperature, p H, or dissolved oxygen(DO). However, when velocity decreased to 0.061 m/s, water depth increased abruptly. In addition, DO displayed a sudden drop and the trend in p H changed from increasing to decreasing, while water temperature showed an opposite trend, indicating the existence of a transition zone from the river to the reservoir.     

Fractal analysis applied to faults and earthquakes——A case study of China

Ｆｒａｃｔａｌａｎａｌｙｓｉｓａｐｐｌｉｅｄｔｏｆａｕｌｔｓａｎｄｅａｒｔｈｑｕａｋｅｓ———ＡｃａｓｅｓｔｕｄｙｏｆＣｈｉｎａＪＩＡＮＷＡＮＧ（王建）ＸＩＡＯＨＵＡＺＨＵ（朱晓华）ＹＯＮＧＨＵＩＸＵ（徐永辉）ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｇ...     

Comparison of 1D non-linear simulations to strong-motion observations: A case study in a swampy site of French Antilles (Pointe-à-Pitre,Guadeloupe)

Observations from many recent strong motion events have shown the importance of local soil conditions and non-linear soil behaviour on the seismic ground response (site effects). As demonstrated by previous seismic microzoning studies (Lebrun et al.) [1]), as well as by at least three historical major earthquakes, Pointe-à-Pitre is prone to strong site effects, due to the particular geology of the area. In this paper, we present a comparison between the strong-motion data available from the stations operating on the swampy site of Pointe-à-Pitre airport and the ground motions derived from 1D non-linear finite element simulations.Results show that, for moderate to strong ground motions, 1D simulations reproduce the main characteristics of site response in terms of duration, energy distribution, amplitude and frequency content. It also shows the importance of very superficial soft layers as peat or saturated mud in low frequency site effects simulations. This point is important for further engineering studies since such very soft formations overlain by stiffer landfills are commonly expected in the Antilles context. Our work also shows that Anderson's criteria, used to quantify the goodness-of-fit of simulated ground motions to the observed ones, appear to be an interesting diagnostic tool for testing the quality of numerical simulations from an engineering point of view.     

Modeling urban growth with GIS based cellular automata and least squares SVM rules: a case study in Qingpu–Songjiang area of Shanghai,China

A critical issue in urban cellular automata (CA) modeling concerns the identification of transition rules that generate realistic urban land use patterns. Recent studies have demonstrated that linear methods cannot sufficiently delineate the extraordinary complex boundaries between urban and non-urban areas and as most urban CA models simulate transitions across these boundaries, there is an urgent need for good methods to facilitate such delineations. This paper presents a machine learning CA model (termed MachCA) with nonlinear transition rules based on least squares support vector machines (LS-SVM) to simulate such urban growth. By projecting the input dataset into a high dimensional space using the LS-SVM method, an optimal hyper-plane is constructed to separate the complex boundaries between urban and nonurban land, thus enabling the retrieval of nonlinear CA transition rules. In the MachCA model, the transition rules are yes–no decisions on whether a cell changes its state or not, the rules being dynamically updated for each iteration of the model implementation. The application of the MachCA for simulating urban growth in the Shanghai Qingpu–Songjiang area in China reveals that the spatial configurations of rural–urban patterns can be modeled. A comparison of the MachCA model with a conventional CA model fitted by logarithmic regression (termed LogCA) shows that the MachCA model produces more hits and less misses and false alarms due to its capability for capturing the spatial complexity of urban dynamics. This results in improved simulation accuracies, although with only less than 1 % deviation between the overall errors produced by the MachCA and LogCA models. Nevertheless, the way MachCA model use in retrieving the transition rules provides a new method for simulating the dynamic process of urban growth.     

Parameterization of the Ångström–Prescott formula based on machine learning benefit estimation of reference crop evapotranspiration with missing solar radiation data

Accurately estimated reference evapotranspiration (ET₀) is essential to regional water management. The FAO recommends coupling the Penman–Monteith (P-M) model with the Ångström–Prescott (A-P) formula as the standard method for ET₀ estimation with missing R_s measurements. However, its application is usually restricted by the two fundamental coefficients (a and b) of the A-P formula. This paper proposes a new method for estimating ET₀ with missing R_s by combining machine learning with physical-based P-M models (PM-ET₀). The benchmark values of the A-P coefficients were first determined at the daily, monthly, and yearly scales, and further evaluated in R_s and ET₀ estimates at 80 national R_s measuring stations. Then, three empirical models and four machine-learning methods were evaluated in estimating the A-P coefficients. Machine learning methods were also used to estimate ET₀ (ML-ET₀) to compare with the PM-ET₀. Finally, the optimal estimation method was used to estimate the A-P coefficients for the 839 regular weather stations for ET₀ estimation without R_s measurement for China. The results demonstrated a descending trend for coefficient a from northwest to southeast China, with larger values in cold seasons. However, coefficient b showed the opposite distribution as the coefficient a. The FAO has recommended a larger a but a smaller b for southeast China, which produced the region's largest R_s and ET₀ estimation errors. Additionally, the A-P coefficients calibrated at the daily scale obtained the best estimation accuracy for both R_s and ET₀, and slightly outperformed the monthly and yearly coefficients without significant difference in most cases. The machine learning methods outperformed the empirical methods for estimating the A-P coefficients, especially for the sites with extreme values. Further, ML-ET₀ outperformed the PM-ET₀ with yearly A-P coefficients but underperformed those with daily and monthly ones. This study indicates an exciting potential for combining machine learning with physical models for estimating ET₀. However, we found that using the A-P coefficients with finer time scales is unnecessary to deal with the missing R_s measurements.     

Optimal contour mapping of groundwater levels using universal kriging—a case study

Abstract

Universal kriging is applied to the command area of a set of canal irrigation projects in north-western India to show its applicability for optimal contour mapping of groundwater levels. This command area faces the problem of a rising groundwater table and manifestation of waterlogging over the years at many places. With the use of measured elevations of the water table in September 1990 at 143 observation sites in an area of 4500 km², an omni-directional experimental semivariogram was constructed. The concave upward shape of omni-directional experimental semivariogram indicated the non-stationarity of the data and so the need for universal kriging. Directional semivariograms were calculated to find out the direction along which there is least drift. This directional semivariogram was considered as the underlying semivariogram and various theoretical semivariogram models were fitted to it. The drift order was estimated from the cross-validation procedure. The model and drift order finally selected were used to estimate the groundwater levels and corresponding estimation variances at the nodes of a square grid of 2 km × 2 km, and to develop the corresponding contour map.     

Fractal analysis applied to faults and earthquakes—A case study of China

The characteristics and correlation of faults and earthquakes are discussed based on fractal and statistical analysis of the earthquakes in the last 500 years and the active faults in China. It is found that fractal relationship exists between the frequency and the length of the active faults, and the fractal dimension is 1.70 in the continental region of China, and 1.40 in the northwest China. The fractal relationship also exists between the frequency and the scales of earthquakes during the last five centuries and the fractal dimension is 1.30 for the whole continental region of China and 1.08 for the northwest China. The differences of the fractal dimensions between the active faults and the earthquakes indicate that some of the active faults have not caused earthquakes during the last 500 years. The differences of fractal dimensions of the active faults and earthquakes between the northwest China and the whole continental region of China suggest that the frequency of strong earthquakes is greater in northwest China than that of the average level of China, because the number of longer active faults is larger in northwest China than that of the average in whole China. Thus, the fractal analysis is an effective method for studies of faults and earthquakes.     

Influence of attenuation and site on microearthquakes’ spectra in Shillong region, of Northeast, India: A case study

We examine the influence of attenuation and site on the spectra of microearthquakes having origin within the Shillong region. The ratios of spectral amplitudes at lower and higher frequencies are measured for three different stations at varying epicentral distances to estimate Q value for both P- and S-wave in near and sub-surface layer. The average estimates of Q _P and Q _S are found to be 178 and 195. The ratio of Q _S to Q _P emerges to be greater than unity in major parts of the Shillong area, suggesting dominance of dry crust prevailing in Shillong region. The variation in corner frequencies for these spectra is inferred to be characteristics of the site. Besides, the disparity in spectral content with reference to hard rock site yields the inference that the incoming seismic signals get amplified considerably while traversing from southern part to northeastern part of Shillong, best outlined at 2 to 5 Hz, which is well corroborated by the existing lithology.     

Fish predation on sympatric and allopatric prey—A case study of Ponto-Caspian gobies,European bullhead and amphipods

Due to the increasing number of biological invasions, more and more non-native species become components of already existing food chains and new interactions develop within communities. In our study, we checked whether (1) the predation preferences depended on sympatric or allopatric occurrence of predator and prey (a predator may choose the well-known prey or rather benefit from the naïvety of the novel one) and (2) fish preferences depended on prey susceptibility to fish predation (ability to hide, active predator avoidance) and/or on its palatability. We studied foraging efficiency of two species of Ponto-Caspian gobies (the round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris) and the European bullhead Cottus gobio on two species of amphipods—Ponto-Caspian Dikerogammarus villosus and non-invasive Gammarus fossarum, occurring in Central and Western Europe. The gammarids were offered to fish with or without shelters and as mobile individuals or immobilized to test the effect of their hiding ability, mobility and palatability on fish predation. Fish selectivity was exhibited only in trials with motile prey, where all tested predators preferred G. fossarum over D. villosus, showing that their selectivity was independent of prey origin. No selectivity was observed for immobilized amphipods. When shelters were present, the predation was lowest. Thus, predator preferences depended on prey behavioural traits (effective shelter utilization and/or activity reduction) rather than on their palatability. Effective predator preference of G. fossarum over D. villosus may be one of the reasons of the successful invasion of the latter to the European inland waters.