Hydrological dynamics of prairie pothole wetlands: Dominant processes and landscape controls under contrasted conditions

Numerous studies have examined the impact of prairie pothole wetlands on overall watershed dynamics. However, very few have looked at individual wetland dynamics across a continuum of alteration status using subdaily hydrometric data. Here, the importance of surface and subsurface water storage dynamics in the prairie pothole region was documented by (1) characterizing surface fill–spill dynamics in intact and consolidated wetlands; (2) quantifying water‐table fluctuations and the occurrence of overland flow downslope of fully drained wetlands; (3) assessing the relation (or lack thereof) between intact, consolidated or drained wetland hydrological behaviour, and stream dynamics; and (4) relating wetland hydrological behaviour to landscape characteristics. Focus was on southwestern Manitoba, Canada, where ten intact, three consolidated, seven fully drained wetlands, and a nearby creek were monitored over two years with differing antecedent storage conditions. Hourly hydrological time series were used to compute behavioural metrics reflective of year‐specific and season‐specific wetland dynamics. Behavioural metrics were then correlated to wetland physical characteristics to identify landscape controls on wetland hydrology. Predictably, more frequent spillage or overland flow was observed when antecedent storage was high. Consolidated wetlands had a high degree of water permanence and a greater frequency of fill–spill events than intact wetlands. Shallow and highly responsive water tables were present downslope of fully drained wetlands. Potential wetland–stream connectivity was also inferred via time‐series analysis, while some landscape characteristics (e.g., wetland surface, catchment area, and storage volume) strongly correlated with wetland behavioural metrics. The nonstationarity of dominant processes was, however, evident through the lack of consistent correlations across seasons. This, therefore, highlights the importance of combining multiyear high‐frequency hydrometric data and detailed landscape analyses in wetland hydrology studies.     

Assessment of Some Hydraulic Properties of Slime Slurries from Sand Mining Pits Using a Modified Triaxial Cell

The generation of massive volume of slimes from sand mining industry ascertains the need for effective waste treatment. The application of slimes in landfill barrier construction works has been identified as one of the processes that can be used to reduce their volume, enabling in this way the rehabilitation of dangerous sites. This article presents a modified triaxial cell specially built to investigate high water content soils and discusses the results obtained from the investigation of the hydraulic properties of two slimes. The results of laboratory filter cake tests show that the slimes have reasonably good sealing capacities due to the formation of a cake layer on other porous materials upon draining. A relatively low hydraulic conductivity (1.5–3 × 10⁻⁹ m/s) was achieved, once the cake layer was formed. This is close to the prescribed 1 × 10⁻⁹ m/s required by the local environmental governmental authority for a landfill hydraulic barrier material, indicating their potential suitability as landfill barrier.     

Mechanical Behaviour of Reservoir Rock Under Brine Saturation

Acoustic emissions (AE) and stress–strain curve analysis are well accepted ways of analysing crack propagation and monitoring the various failure stages (such as crack closure, crack initiation level during rock failure under compression) of rocks and rock-like materials. This paper presents details and results of experimental investigations conducted for characterizing the brittle failure processes induced in a rock due to monocyclic uniaxial compression on loading of two types of sandstone core samples saturated in NaCl brines of varying concentration (0, 2, 5, 10 and 15 % NaCl by weight). The two types of sandstone samples were saturated under vacuum for more than 45 days with the respective pore fluid to allow them to interact with the rocks. It was observed that the uniaxial compressive strength and stress–strain behaviour of the rock specimens changed with increasing NaCl concentration in the saturating fluid. The acoustic emission patterns also varied considerably for increasing ionic strength of the saturating brines. These observations can be attributed to the deposition of NaCl crystals in the rock’s pore spaces as well some minor geo-chemical interactions between the rock minerals and the brine. The AE pattern variations could also be partly related to the higher conductivity of the ionic strength of the high-NaCl concentration brine as it is able to transfer more acoustic energy from the cracks to the AE sensors.     

Ion-temperature-gradient driven modes in dust-contaminated plasma with nonthermal electron distribution and dust charge fluctuations

The effect of nonthermal electrons on ion-temperature-gradient (ITG) driven modes is investigated in the presence of variable dust charge and ion shear flow. The dust charge fluctuating expression is obtained in the presence of kappa distributed electrons. A dispersion relation is derived and analyzed numerically by choosing space plasma parameters of Jupiter/Saturn magnetospheres. It is found that the presence of nonthermal electrons population reduces the growth rate of ITG mode driven instability. The effects of ion temperature, electron density and magnetic field variation on the growth rate of ITG instability are presented numerically. It is also pointed out that the present results will be useful to understand the ITG driven modes with variable dust charge and kappa distributed electrons, present in most of the space plasma environments.     

Integrating facies-based Bayesian inversion and supervised machine learning for petro-facies characterization in the Snadd Formation of the Goliat Field,south-western Barents Sea

Seismic petro-facies characterization in low net-to-gross reservoirs with poor reservoir properties such as the Snadd Formation in the Goliat field requires a multidisciplinary approach. This is especially important when the elastic properties of the desired petro-facies significantly overlap. Pore fluid corrected endmember sand and shale depth trends have been used to generate stochastic forward models for different lithology and fluid combinations in order to assess the degree of separation of different petro-facies. Subsequently, a spectral decomposition and blending of selected frequency volumes reveal some seismic fluvial geomorphological features. We then jointly inverted for impedance and facies within a Bayesian framework using facies-dependent rock physics depth trends as input. The results from the inversion are then integrated into a supervised machine learning neural network for effective porosity discrimination. Probability density functions derived from stochastic forward modelling of endmember depth trends show a decreasing seismic fluid discrimination with depth. Spectral decomposition and blending of selected frequencies reveal a dominant NNE trend compared to the regional SE–NW pro-gradational trend, and a local E–W trend potentially related to fault activity at branches of the Troms-Finnmark Fault Complex. The facies-based inversion captures the main reservoir facies within the limits of the seismic bandwidth. Meanwhile the effective porosity predictions from the multilayer feed forward neural network are consistent with the inverted facies model, and can be used to qualitatively highlight the cleanest regions within the inverted facies model. A combination of facies-based inversion and neural network improves the seismic reservoir delineation of the Snadd Formation in the Goliat Field.     

Acoustic and petrophysical properties of mechanically compacted overconsolidated sands: part 1 – experimental results

This paper part one is set out to lay primary observations of experimental compaction measurements to form the basis for rock physics modelling in paper part two. P- and S-wave velocities and corresponding petrophysical (porosity and density) properties of seven unconsolidated natural sands with different mineralogical compositions and textures are reported. The samples were compacted in a uniaxial strain configuration from 0.5 up to 30 MPa effective stresses. Each sand sample was subjected to three loading cycles to study the influence of stress reduction on acoustic velocities and rock physical properties with the key focus on simulating a complex burial history with periods of uplift. Results show significant differences in rock physical properties between normal compaction and overconsolidation (unloaded and reloaded). The differences observed for total porosity, density, and P- and S-wave velocities are attributed to irrecoverable permanent deformation. Microtextural differences affect petrophysical, acoustic, elastic and mechanical properties, mostly during normal consolidation but are less significant during unloading and reloading. Different pre-consolidation stress magnitudes, stress conditions (isotropic or uniaxial) and mineral compositions do not significantly affect the change in porosity and velocities during unloading as a similar steep velocity–porosity gradient is observed. The magnitude of change in the total porosity is low compared to the associated change in P- and S-wave velocities during stress release. This can be explained by the different sensitivity of the porosity and acoustic properties (velocities) to the change in stress. Stress reduction during unloading yields maximum changes in the total porosity, P- and S-wave velocities of 5%, 25%, and 50%, respectively. These proportions constitute the basis for the following empirical (approximation) correlations: Δϕ ∼ ±5 ΔV_P and ΔV_P ∼ ±2ΔV_S. The patterns observed in the experiments are similar to well log data from the Barents Sea. Applications to rock physics modelling and reservoir monitoring are reported in a companion paper.     

Impacts of river bank erosion on population displacement in the lower Brahmaputra (Jamuna) floodplain

"This study has attempted to focus on dimensions and impacts of displacement by river bank erosion in the lower Brahmaputra (Jamuna) floodplain of Bangladesh. Based on a survey of 547 randomly selected households, it was observed that about two thirds of the floodplain inhabitants were displaced at least once in their life time." The socioeconomic consequences are discussed, and implications for development planning are considered.     

Climatic changes in Bahrain

Local and regional studies of climatic patterns confirm that temperatures are rising in the Arabian Gulf area. Further warming of the region, which is already unbearably hot is an environmental catastrophe on a new scale. It has potential to violently disrupt virtually every natural ecosystem and many of the structures and institutions that people depend on. It seems that the Arabian Gulf region is also a part of global warming or the green house effect. This paper analyzes temperatures, rainfall, humidity, sunshine, evaporation and wind speeds. The effect of the Gulf War or Desert Storm has also been included. The study confirms that temperature is rising at a rate of 1.4°C in 100 years. In the beginning a brief discussion of geography, culture, water resources and modern development in Bahrain is given to introduce the country.     

Perspectives of Natural Disasters in East and South Asia,and the Pacific Island States: Socio-economic Correlates and Needs Assessment

The regions of East and South Asia, and the Pacific Islands are among the most-hazardprone areas in the world. Because of this, during the last century, most of the humancasualties of `natural-triggered' disasters have taken place in this region. This circumstance therefore has become a major global humanitarian concern. Another major concern, specifically for the donor agencies, is the damage sustained by infrastructure resulting from environmental disasters. These recurrent loses take away a significant proportion of the cumulative economic gains accrued from development investments over many years.Stepwise multiple regression results substantiated the fact that many of the socio-economic and demographic variables significantly influence disaster-related deaths and injuries in this part of the world. A comparative temporal analysis has shown that, over the past two decades, demographic variables have become prominent predictors of disaster-loss in South, Southeast and East Asian and the Pacific states.Many countries of the region are lagging behind in understanding and recognizing thebroader scope of disaster mitigation and management. Emerging needs and awarenessamong the decision-makers and the general public, however, have prompted institutionsin many countries to initiate a critical review of the prevailing approaches. Thecountry-specific disaster-management capacities and needs in the region vary widely.There are many differences in historical courses, institutional and administrative settings, sociocultural characteristics, as well as political and economic systems. Development of a common institutional framework for the region, therefore, seems unfeasible. Based upon a regional review, it has become clear that the research calls for improving the understanding of the significance of disaster mitigation and management in light of sustainable development and the emerging global issues. In addition, aspects of human resource development to enhance institutional mitigation and response capacities are emphasized.