Ground Water Security and Drought in Africa: Linking Availability,Access, and Demand

Drought in Africa has been extensively researched, particularly from meteorological, agricultural, and food security perspectives. However, the impact of drought on water security, particularly ground water dependent rural water supplies, has received much less attention. Policy responses have concentrated on food needs, and it has often been difficult to mobilize resources for water interventions, despite evidence that access to safe water is a serious and interrelated concern. Studies carried out in Ghana, Malawi, South Africa, and Ethiopia highlight how rural livelihoods are affected by seasonal stress and longer-term drought. Declining access to food and water is a common and interrelated problem. Although ground water plays a vital role in buffering the effects of rainfall variability, water shortages and difficulties in accessing water that is available can affect domestic and productive water uses, with knock-on effects on food consumption and production. Total depletion of available ground water resources is rarely the main concern. A more common scenario is a spiral of water insecurity as shallow water sources fail, additional demands are put on remaining sources, and mechanical failures increase. These problems can be planned for within normal development programs. Water security mapping can help identify vulnerable areas, and changes to monitoring systems can ensure early detection of problems. Above all, increasing the coverage of ground water–based rural water supplies, and ensuring that the design and siting of water points is informed by an understanding of hydrogeological conditions and user demand, can significantly increase the resilience of rural communities to climate variability.     

Modelling dam-break flows over mobile beds using a 2D coupled approach

Dam-break flows usually propagate along rivers and floodplains, where the processes of fluid flow, sediment transport and bed evolution are closely linked. However, the majority of existing two-dimensional (2D) models used to simulate dam-break flows are only applicable to fixed beds. Details are given in this paper of the development of a 2D morphodynamic model for predicting dam-break flows over mobile beds. In this model, the common 2D shallow water equations are modified, so that the effects of sediment concentrations and bed evolution on the flood wave propagation can be considered. These equations are used together with the non-equilibrium transport equations for graded sediments and the equation of bed evolution. The governing equations are solved using a matrix method, thus the hydrodynamic, sediment transport and morphological processes can be jointly solved. The model employs an unstructured finite volume algorithm, with an approximate Riemann solver, based on the Roe-MUSCL scheme. A predictor–corrector scheme is used in time stepping, leading to a second-order accurate solution in both time and space. In addition, the model considers the adjustment process of bed material composition during the morphological evolution process. The model was first verified against results from existing numerical models and laboratory experiments. It was then used to simulate dam-break flows over a fixed bed and a mobile bed to examine the differences in the predicted flood wave speed and depth. The effects of bed material size distributions on the flood flow and bed evolution were also investigated. The results indicate that there is a great difference between the dam-break flow predictions made over a fixed bed and a mobile bed. At the initial stage of a dam-break flow, the rate of bed evolution could be comparable to that of water depth change. Therefore, it is often necessary to employ the turbid water governing equations using a coupled approach for simulating dam-break flows.     

中国城市群区域城际轨道交通布局模式

我国城市密集区与城市群的迅速发展,对交通网络化、现代化的需求日益迫切,而城际轨道交通是城市群发展的重要条件和前提。国外发达国家发展的经验表明,城际轨道交通是城市群客流运输最佳的交通方式选择,两者相互影响、互为促进,城市群区域和城际轨道交通之间的空间结构存在着必然的空间映射关系。基于此,本文根据我国城市群发展现状及其区域空间结构发展的5种模式,相应提出放射型、钟摆型、串珠型和网络型等4种城际轨道交通布局形式,并阐述各自特点。在未来一定时期,国内城际轨道交通将蓬勃发展,必须根据城市群区域空间结构发展模式,进行科学规划和布局形式的选择,以有效满足日益庞大的客流需求和推动城市群发展战略的实现。     

Assessing drought in the drylands of northeast Brazil under regional warming exceeding 4 °C

Natural Hazards - Historically, during periods of extreme drought, food security in the drylands of the semiarid region of Northeast Brazil (NEB) is under severe risk due to agricultural collapse....     

Radiometric dating of the Middle Palaeolithic tool industry and associated fauna of Pin Hole Cave,Creswell Crags,England

Uranium-series dating of derived speleothem suggests that the sediments enclosing a Middle Palaeolithic stone artefact assemblage in Pin Hole Cave probably accumulated after about 64 ka, and ¹⁴C dates indicate a likely age of > 40 ka for the large mammal fauna associated with it. Electron spin resonance data from the fauna conform with these age constraints and are consistent with accumulation between 38 and 50 ka. This evidence supports the view that Britain was recolonised by hominids during Oxygen Isotope Stage 3. Stratigraphically higher stone tool industries demonstrate the local presence of both early Upper and late Upper Palaeolithic cultures. © 1998 John Wiley & Sons, Ltd.     

Application of Multi-well Subsidence Analysis of the Beryl Embayment,Viking Graben, Northern North Sea

1 Introduction A series of studies have indicated that there were two extensional phases in the North Sea (Fig. 1). An earlier period (Late Permian-Early Triassic) of rifting occurred widely in these areas, with predominant extension direction of W-E (F?rseth, 1996; F?rseth et al., 1997). In contrast to the widely distributed Permo-Triassic extension, Jurassic extension in the North Sea were generally much more localized into the three main rift arms (Fig. 1): the Viking Graben, Moray…