Estimating water balance components of tropical wetland lakes in the Pantanal dry season,Brazil

Abstract

Water balance studies with stable water isotopes have rarely been conducted in remote and tropical wetland areas. As such, little is known regarding the water balance and groundwater–surface water interaction in the Pantanal, one of the largest and most pristine wetlands in the world. We applied MINA TrêS, a water balance model utilizing stable water isotopes (δ¹⁸O, δ²H) and chloride (Cl^-) to assess the dry-season hydrological processes controlling groundwater–surface water interactions and the water balance of six floodplain lakes in the northern Pantanal, Brazil. Qualitatively, all lakes exhibited similarity in hydrological controls. Quantitatively, they differed significantly due to morphological differences in controlling groundwater inflow and lake volume. Our approach is readily transferable to other remote and tropical wetland systems with minimal data input requirements, which is useful in regions with sparse hydrometric monitoring.

Editor Z.W. Kundzewicz     

Horizontal rough fracture type curves for groundwater movement

Abstract

Type curves are derived analytically for radial flow in rough horizontal fractures toward a well. The basic assumptions are that there is no turbulent flow near the borehole and the well storage is ignored. The basis of the methodology is to write explicit expressions for the continuity and cubic law flow equations, which are combined using a Boltzmann transformation leading to a simple ordinary differential equation for groundwater movement. Solutions are presented as a set of type curves for different fracture apertures. It is observed that the solutions provide a method of uniquely identifying fracture hydraulic parameters when the fracture is smooth, but pose ambiguity for rough fracture parameter estimations. However, large time portions of these type curves appear as straight lines on semi-logarithmic paper, which provides a unique way for rough fracture parameter determination. Identification of the fracture parameters, namely, the aperture and relative roughness, is possible in a unique manner with the use of these lines and the dimensionless time drawdown concept. The cubic law is the asymptotic behaviour, either for large times or large fracture apertures. Prior to this asymptotic part, there is a non-cubic portion which gives rise to systematic deviations from the cubic law. The technique presented is useful, especially for evaluating pumping tests from a single major fracture isolated by packers.     

The impact of subsurface conceptualization on land energy fluxes

There is a significant body of work demonstrating the importance of hydrologic control on land energy feedbacks. Yet, quantitative data on aquifer conductivity can be difficult to assemble. Furthermore, how subsurface uncertainty propagates into land-surface processes is not well understood. This study analyzes the impact of aquifer characterization on land energy fluxes, using a coupled hydrology–land-surface model. Four gridded subsurface conductivity fields are developed for the Upper Klamath basin using two data sources and different levels of imposed heterogeneity. Each model is forced with the same transient, observed meteorology for 3 years prior to the final year presented here. Results are analyzed to quantify the impact of subsurface heterogeneity on groundwater surface water interactions and spatial patterns in hydrologic variables. Analysis shows that heterogeneity does not fundamentally alter the connection between groundwater and land surface processes. However, differences between scenarios impact the extent and location of the critical zone.     

Influence of capillary-pressure models on CO2 solubility trapping

The typical shape of a capillary-pressure curve is either convex (e.g., Brooks–Corey model) or S-shaped (e.g., van Genuchten model). It is not universally agreed which model reflects natural rocks better. The difference between the two models lies in the representation of the capillary entry pressure. This difference does not lead to significantly different simulation results for modeling CO₂ sequestration in aquifers without considering CO₂ dissolution. However, we observe that the van-Genuchten-type capillary-pressure model accelerates CO₂ solubility trapping significantly compared with the Brooks–Corey-type model. We also show that the simulation results are very sensitive to the slope of the van-Genuchten-type curve around the entry-pressure region. For the representative examples we study, the differences can be so large as to have complete dissolution of the CO₂ plume versus persistence of over 50% of the plume over a 5000-year period.The cause of such sensitivity to the capillary-pressure model is studied. Particularly, we focus on how the entry pressure is represented in each model. We examine the mass-transfer processes under gravity-capillary equilibrium, molecular diffusion, convective mixing, and in the presence of small-scale heterogeneities. Laboratory measurement of capillary-pressure curves and some important implementation issues of capillary-pressure models in numerical simulators are also discussed. Most CO₂ sequestration simulations in the literature employ one of the two capillary-pressure models. It is important to recognize that these two representations lead to very different predictions of long-term CO₂ sequestration.     

Geospatial predictive modelling of the Neolithic archaeological sites of Magnesia in Greece

Abstract

Sources of heterogeneous geospatial data such as the elevation, the slope, the aspect, the water network and the current settlements related to the known Neolithic archaeological sites of Magnesia, are used in an attempt to confirm the existence and allow for the prediction of other archaeological sites using predictive modelling theory. Predictive modelling allows the update of the problem solving strategy as soon as new data layers are available. The Dempster–Shafer Theory also commonly referred to as evidential reasoning (ER) is used to compose probability maps of areas of archaeological interest from physiographical and historical data. The advantage of this theory is that the ignorance is quantified and used to compose the probability maps named as belief, plausibility and belief interval for the archaeological sites. The final digital probability maps show that the Neolithic archaeological sites can be detected in the prefecture of Magnesia. This research study forms a methodological tool for the prediction of new archaeological sites in other areas of archaeological interest according to the physiographical and historical characteristics of the archaeological period being examined. It also contributes to the digital earth modelling and archaeological site protection, one of the most critical and challenging global initiatives.     

Web-based visualization of large 3D urban building models

Adaptive rendering of large urban building models has become an important research issue in three-dimensional (3D) geographic information system (GIS) applications. This study explores a way for rendering web-based 3D urban building models. A client–server hybrid rendering approach is presented for large 3D city models, stored on a remote server through a network. The approach combines an efficient multi-hierarchical building representation with a novel image-based method, 3D image impostor generated on demand by a remote server. This approach allows transferring complex scenes progressively while keeping high visualization quality. We also evaluated the rendering and data transferring performance of the proposed approach.     

Texture augmented detection of macrophyte species using decision trees

Image classification using multispectral sensors has shown good performance in detecting macrophytes at the species level. However, species level classification often does not utilize the texture information provided by high resolution images. This study investigated whether image texture provides useful vector(s) for the discrimination of monospecific stands of three floating macrophyte species in Quickbird imagery of the South Nation River. Semivariograms indicated that window sizes of 5 × 5 and 13 × 13 pixels were the most appropriate spatial scales for calculation of the grey level co-occurrence matrix and subsequent texture attributes from the multispectral and panchromatic bands. Of the 214 investigated vectors (13 Haralick texture attributes * 15 bands + 9 spectral bands + 10 transformations/indices), feature selection determined which combination of spectral and textural vectors had the greatest class separability based on the Mann–Whitney U-test and Jefferies–Matusita distance. While multispectral red and near infrared (NIR) performed satisfactorily, the addition of panchromatic-dissimilarity slightly improved class separability and the accuracy of a decision tree classifier (Kappa: red/NIR/panchromatic-dissimilarity – 93.2% versus red/NIR – 90.4%). Class separability improved by incorporating a second texture attribute, but resulted in a decrease in classification accuracy. The results suggest that incorporating image texture may be beneficial for separating stands with high spatial heterogeneity. However, the benefits may be limited and must be weighed against the increased complexity of the classifier.     

Investigating the land use characteristics of urban integration based on remote sensing data: experience from Guangzhou and Foshan

Abstract

Urban integration is an increasingly popular phenomenon. It is important to characterize the dynamic processes of urban integration from the perspective of geography. However, previous studies mainly focussed on the overall characteristics of a single entity and failed to consider inter-city influences. Therefore, this study aims to systematically investigate this phenomenon. Firstly, spatial clustering technique and landscape metric were used to analyze the temporal change of spatial layout. Secondly, we built multiple ring buffers of city boundary to reveal the directional differences in urban expansion. Lastly, we compared the observed land use data with the results simulated by cellular automata model. These experiments have shown that the urban expansion characteristics during the urban integration process are rather different from those of a single city, and the above methodology can effectively characterize the urban integration phenomenon. The successful example of Guangzhou–Foshan integration could also provide practical experience for other similar attempts.     

Space,time, and situational awareness in natural hazards: a case study of Hurricane Sandy with social media data

ABSTRACT

Various methods have been developed to investigate the geospatial information, temporal component, and message content in disaster-related social media data to enrich human-centric information for situational awareness. However, few studies have simultaneously analyzed these three dimensions (i.e. space, time, and content). With an attempt to bring a space–time perspective into situational awareness, this study develops a novel approach to integrate space, time, and content dimensions in social media data and enable a space–time analysis of detailed social responses to a natural disaster. Using Markov transition probability matrix and location quotient, we analyzed the Hurricane Sandy tweets in New York City and explored how people’s conversational topics changed across space and over time. Our approach offers potential to facilitate efficient policy/decision-making and rapid response in mitigations of damages caused by natural disasters.     

无机生油假说及其在中国的应用前景

无机生油假说认为,原油和天然气和近地表的生物物质没有根本联系,它们是生成于地幔内的非生物来源的碳氢化合物。因而油气不是一个不可再生资源,而是一个可再生资源。无机生油假说得到地质学、物理学和化学等三个基本学科的支持。在地质观察上,发现全球许多大油田的油气储藏与原始生物物质之间数量上有巨大落差,难于解释它们是由生物生成的。此外,有许多地区在结晶基底或变质基底内,或直接位于其上的沉积岩中发现石油。从生物生油假说来说,也是无法理解的。在化学上,早在二战期间,德国已由人工合成石油(费托合成),并生产了占德国战争中用油的9%的石油。无可争辩地说明,无机可以生成石油。根据化学(物理学)热力学理论分析确认,甲烷是唯一一种在标准温压条件(温度为298.15 K;压力为101325 Pa)下稳定的碳氢化合物,从甲烷形成正常烷属烃只有在压力>3×106kPa、温度>700°C时(相当于地下深度约100 km)才有可能。在地壳内的温压条件下由生物变质形成石油的假说,与化学热力学的基本原则相抵触。从氧化的有机分子,如碳水化合物(C6H12O6)形成较高的碳氢化合物在任何条件下都是不可能的。根据我国长期对深部构造的研究,笔者认为在中国东部及西太平洋蘑菇云岩石圈地幔发育的地区是寻找巨型无机油气田的有利地区,建议在发育蘑菇云岩石圈地幔地区开展无机油气田的勘探,并在无机油气田远景地区布置超深参数钻,以评价含油气远景。另外建议加强物探工作,尤其是研究地震勘探处理基底内三维含油气构造的技术。