Air and water entrapment in the vicinity of the water table

A laboratory tank was used to study entrapment of water in coarse sand lenses above the water table and of air in coarse sand lenses below the water table. Monitoring of these experiments involved a combination of visual inspection, measurement of moisture content, and measurement of air/water pressure. The medium consisted of coarse sand lenses with various degrees of vertical connectivity embedded within a fine sand matrix. Experiments were performed under conditions of both drainage (from a fully saturated medium) and imbibition. Observations during drainage included: (1) water was trapped in the coarse sand zones above the water table at heights significantly greater than anticipated from consideration of capillary rise in the coarse sand; (2) rapid drainage of these same coarse zones occurred when air penetrated into these zones through the surrounding fine sands; and (3) prior to the time of penetration of the coarse sand by air, water pressure in the coarse zone dropped significantly below atmospheric pressure. Observations during imbibition included: (1) entrapment of air within coarse sands below the water table, (2) the pore fluids in these zones varied spatially from predominantly air to predominantly water, and (3) pressure in the trapped air phase was significantly greater than pressure in the water phase in the surrounding fine sand. Overall, these results demonstrated significant sensitivity to the geometry of the coarse sand inclusions, particularly the vertical connectivity of the coarse sand lens.     

Thermoremanent magnetization (TRM) of lunar samples

The TRM of the lunar breccia 10048-55 and the crystalline rocks 12053-47 and 14053-48 have been investigated. TRM is acquired linearly by 12053-47 and 10048-55 in fields of 100 to 1 oe. In contrast, the TRM of 14053-48 departs from linearity in the same range of fields. The AF stability of TRM acquired by the samples varies markedly. 10048-55 and 12053-47 are of intermediate hardness, such as would be expected for a TRM carried at least in part by fine grain particles of iron having high coercivity. 14053-48 has extremely soft TRM which is most probably carried predominantly by multidomain iron. Thermal demagnetization of the TRM of 10048-55 revealed well distributed blocking temperatures, but the TRM of 14053-48 has markedly bimodal blocking temperatures. Comparison of the characteristics of the NRM and the TRM of the three samples suggest that only the NRM of 14053-48 is likely to be primarily thermal in origin.     

GIS in Participatory Research: Assessing the Impact of Landmines on Communities in North-west Cambodia

The view of GIS, adopted by many, as an undemocratic and divisive technology is perhaps most poignant in settings where financial and skills‐based resources are limited, notably in lower‐income countries. Where those countries are also recovering from a period of military conflict there would at first sight seem to be little opportunity for employing GIS as part of a socially‐sensitive approach to ‘development’. This paper explores the potential for using GIS in participatory approaches to gathering and analysing geographical information on human‐environment interactions in post‐conflict settings. We discuss empirical work from northwest Cambodia where GIS and participatory methods have been integrated to assess risk to local communities from landmines and to develop priorities for landmine clearance. In juxtaposing ‘official’, spatially‐referenced data with indigenous geographical knowledge in this study we seek to privilege meaningful geographical understandings over conventional notions of spatial ‘accuracy’. In so doing we carry out a Participatory Mine Impact Assessment (PMIA) to explore spatial activities among local populations in mine‐contaminated communities and to help identify improved strategies for returning refugees in re‐establishing livelihoods.     

The Geography of Racisms in NSW: A theoretical exploration and some preliminary findings from the mid-1990s

The spatial variation of racisms is an under-researched field of inquiry, certainly in Australia. This paper explores the geographies of racism in New South Wales. Responses to three opinion polls conducted between 1994 and 1996 were used to construct patterns of racisms across NSW. Preliminary findings suggest a substantive degree of racism in NSW. There was little evidence of an urban-rural variation in terms of ethnocentrism. Examination of regional variations confounds this simple division. Social Constructionist theory is put forward as a spatially sensitive theory for understanding and responding to the geographies of racism. The identification of regional variations in racism is crucial to the development of regionally specific anti-racism campaigns. This paper highlights the need for more comprehensive analyses of the varying causes and remedies for racisms.     

Some factors affecting water yield from mountain ash (Eucalyptus regnans) dominated forests in south-east Australia

An experiment in mountain ash forests in Melbourne's water supply catchments in south-east Australia investigated the impact on long-term water yield of reducing forest density. Fifty-four per cent of basal area was removed from a 17 ha catchment (Black Spur 1) by patch cutting, and the patches were regenerated with mountain ash. A 50% reduction was implemented in Black Spur 3, an 8 ha catchment, through uniform thinning. Uniform thinning was shown to be more effective in enhancing streamflow than patch cutting. A streamflow increase of 25–30% (130–150 mm year⁻¹) was observed after treatment in both catchments. Eleven years later, a treatment effect of 15% was still evident in the selectively thinned catchment (Black Spur 3), but the effect had completely decayed in the patch cut catchment (Black Spur 1).

Research by Melbourne Water has established that streamflow is significantly influenced by forest age. It is hypothesised that this relationship, and the observed decay after patch cutting in Black Spur 1, is largely the result of variation in transpiration. To study the relationship between forest age and transpiration in detail, sap velocity was measured over two summers in four mountain ash plots using the heat-pulse method. The trees on these plots were 50, 90, 150 and 230 years old. On days when measurements were made, the mean sap velocity was not significantly different in the 50-, 90- 230-year-old stands, but was significantly smaller by 14% in the 150-year-old stand. Overstorey sapwood area gradually decreased with plot age, and was 57% lower in the 230-year-old plot than in the 50-year-old plot. When combined with the sap velocity measurements, these data indicated that over the six warmest months of the year, transpiration in the 50-year-old plot was 190 mm more than in the 230-year-old plot. These results support a hypothesis that differences in streamflow between 50-year-old and 230-year-old mountain ash forest can largely be accounted for by differences in transpiration. Further heat-pulse studies in young regrowth and in thinned and unthinned 1939 regrowth will be needed if the streamflow changes in Black Spur 1 and Black Spur 3 are to be fully explained.     

Resident action groups in Sydney: people power or rat‐bags?

This paper presents an analysis of a neglected area of study by geographers; that of resident action groups. During the 1980s there has been a significant increase in the number of resident action groups throughout Sydney. Resident activism has influenced local planning processes, the location of noxious facilities and subsequent urban form. This has initiated important reactions by government at both the local and State levels. Urban collective activisms have been hypothesised as single‐issue, self‐serving nimby groups. However, RAGs are also empowering forces, in which women and men are introduced to the political structures and become engaged in protest and resistance that can challenge the social and spatial order. RAGs can, either singularly or cumulatively, force a re‐aligning of existing power relations, and they can necessitate changed modes of governance (or govern‐mentality).     

Tree-top sampling from a helicopter - a new approach to gold exploration

Foliage from Douglas-fir (Pseudotsuga menziesii) tops was collected from 94 sites around the poorly exposed QR Au deposit in central British Columbia. Locally high concentrations of gold in ashed stems suggest a northwestward (down-ice) dispersion train of Au extending uphill for at least 500 m from the deposit. In addition, a down-slope, hydromorphic dispersion train is evident. All trees sampled are extremely rich in As, but the patterns of As distribution are less clearly related to the mineralization than those of Au enrichment. Summary statistics of analytical data for 35 elements are provided to serve as baseline information for any future studies.The sampling method, which is described in detail, is simple and cost-effective. In one hour the foliage of tree tops from about 50 sites, spaced at intervals of 200 m or more, can be collected by a three-person helicopter crew. The technique is particularly appropriate for rapidly screening rugged or heavily forested terrain, regardless of snow-cover, in order to establish priorities for ground follow-up exploration targets.