Dissertations / Theses on the topic 'Dryland salinity'

Australia is experiencing widespread ecosystem degradation, including dryland salinity, erosion and vegetation loss. Approximately 1 million hectares (5.5%) of the south-west agricultural zone of Western Australia is affected by dryland salinity and is predicted to rise to 5.4 million hectares by 2050. Such degradation is associated with many environmental outcomes that may impact on human health, including a decrease in primary productivity, an increase in the number of invasive species, a decrease in the number of large trees, overall decrease in biodiversity, and an increase in dust production. The resulting degradation affects not only farm production but also farm values. This study examines the effects of such severe and widespread environmental degradation on the physical and mental health of residents. Western Australia has an extensive medical record database which links individual health records for all hospital admissions, cancer cases, births and deaths. For the 15 diseases examined in this project, the study area of the south west of Western Australia (excluding the capital city of Perth) contained 1,570,985 morbidity records and 27,627 mortality records for the 15 diseases examined in a population of approximately 460,000. Environmental data were obtained from the Western Australian Department of Agriculture?s soil and landscape mapping database. A spatial Bayesian framework was used to examine associations between these disease and environmental variables. The Bayesian model detected the confounding variables of socio-economic status and proportion of the population identified as Aboriginal or Torres Strait Islander. With the inclusion of these confounders in the model, associations were found between environmental degradation (including dryland salinity) and several diseases with known environmentally-mediated triggers, including asthma, ischaemic heart disease, suicide and depression. However, once records of individuals who had been diagnosed with coexistent depression were removed from the analysis, the effect of dryland salinity was no longer statistically detectable for asthma, ischaemic heart disease or suicide, although the effects of socio-economic status and size of the Aboriginal population remained. The spatial component of this study showed an association between land degradation and human health. These results indicated that such processes are driving the degree of psychological ill-health in these populations, although it remains uncertain whether this 4 is secondary to overall coexisting rural poverty or some other environmental mechanism. To further investigate this complex issue an instrument designed to measure mental health problems in rural communities was developed. Components of the survey included possible triggers for mental health, including environmental factors. The interview was administered in a pilot study through a telephone survey of a small number of farmers in South-Western Australia. Using logistic regression a significant association between the mental health of male farmers and dryland salinity was detected. However, the sample size of the survey was too small to detect any statistically significant associations between dryland salinity and the mental health of women. The results of this study indicate that dryland salinity, as with other examples of ecosystem degradation, is associated with an increased burden of human disease.

[Truncated abstract] In an era of emerging and resurging infectious diseases, understanding the ecological processes that influence pathogen activity and the influences of anthropogenic change to those are critical. Ross River virus (RRV, Togoviridae: Alphavirus) is a mosquito-borne zoonosis occurring in Australia with a significant human disease burden. In the southwest of Western Australia (WA) RRV is principally vectored by Aedes camptorhynchus Thomson (Diptera: Culicidae), which is halophilic. The inland southwest, the Wheatbelt region, of WA is substantially affected by an anthropogenic salinisation of agricultural land called dryland salinity, which threatens to influence transmission of this arbovirus. This study assessed the ecological impacts of dryland salinity on mosquitoes, mammalian hosts and their interactions to influence the potential for RRV transmission. Many aquatic insect taxa colonise ephemeral water bodies directly as adults or by oviposition. Using a manipulative experiment and sampling from ephemeral water bodies in the Wheatbelt, I demonstrated that salinity of water bodies can modify colonisation behaviour and the distribution of some organisms across the landscape. Halosensitive fauna selected less saline mesocosms for oviposition and colonisation. In particular, Culex australicus Dobrotworksy and Drummond and Anopheles annulipes Giles (Diptera: Culicidae), potential competitors with Ae. camptorhynchus, avoided ovipostion in saline mesocosms and water bodies in the field. This finding suggests salinity influences behaviour and may reduce interspecific interactions between these taxa and Ae. camptorhynchus at higher salinities. Using extensive field surveys of ephemeral water bodies in the Wheatbelt I found mosquitoes frequently colonised ephemeral water bodies, responded positively to rainfall, and populated smaller water bodies more densely than larger water bodies. The habitat characteristics of ephemeral water bodies changed in association with salinity. Consequently there were both direct and indirect associations between salinity and colonising mosquitoes. Ultimately the structure of mosquito assemblages changed with increasing salinity, favouring an increased regional distribution and abundance of Ae. camptorhynchus. The direct implication of this result is secondary salinisation has enhanced the vectorial potential for RRV transmission in the WA Wheatbelt. ... This thesis contributes to an emerging body of research aimed at delineating important ecological processes which determine transmission of infections disease. Collectively the findings in this study suggest dryland salinity enhances the potential for RRV activity in the Wheatbelt. Currently, human RRV notifications in the Wheatbelt do not reflect the salinity-RRV transmission potential in that area, but appear to be associated with dispersal of RRV from the enzootic coastal zone of southwest WA. I speculate dryland salinity is a determinant of potential for RRV transmission, but not activity. Dryland salinity is predicted to undergo a two to four fold expansion by 2050, which will increase the regional potential for RRV activity. Preservation and restoration of freshwater ecosystems may ameliorate the potential for transmission of RRV and, possibly, human disease incidence.

[Truncated abstract] The salinisation of agricultural land, urban infrastructure and natural habitat is a serious and increasing problem in southern Australia. Government funding has been allocated to the problem to attempt to reduce substantial costs associated with degradation of agricultural and non-agricultural assets. Nevertheless, Government funding has been small relative to the size of the problem and therefore expenditure needs to be carefully targeted to interventions that will achieve the greatest net benefits. For intervention to be justified, the level of salinity resulting from private landholder decisions must exceed the level that is optimal from the point of view of society as a whole, and the costs of government intervention must be less than the benefits gained by society. This study aims to identify situations when government intervention is justified to manage dryland salinity that threatens to affect road infrastructure (a public asset). A key gap in the environmental economics literature is research that considers dryland salinity as a pollution that has off-site impacts on public assets. This research developed two hydrological/economic models to achieve this objective. The first was a simple economic model representing external costs from dryland salinity. This model was used to identify those variables that have the biggest impact on the net-benefits possible from government intervention. The second model was a combined hydro/economic model that represents the external costs from dryland salinity on road infrastructure. The hydrological component of the model applied the method of metamodelling to simplify a complex, simulation model to equations that could be easily included in the economic model. The key variables that have the biggest impact on net-benefits of dryland salinity mitigation were the value of the off-site asset and the time lag before the onset of dryland salinity in the absence of intervention. ... In the case study of dryland salinity management in the Date Creek subcatchment of Western Australia, the economics of vegetation-based and engineering strategies were investigated for road infrastructure. In general, the engineering strategies were more economically beneficial than vegetation-based strategies. In the case-study catchment, the cost of dryland salinity affecting roads was low relative to the cost to agricultural land. Nevertheless, some additional change in land management to reduce impacts on roads (beyond the changes justified by agricultural land alone) was found to be optimal in some cases. Reinforcing the results from the simple model, a key factor influencing the economics of dryland salinity management was the urgency of the problem. If costs from dryland salinity were not expected to occur until 30 years or more, the optimal response in the short-term was to do nothing. Overall, the study highlights the need for governments to undertake comprehensive and case-specific analysis before committing resources to the management of dryland salinity affecting roads. There were many scenarios in the modelling analysis where the benefits of interventions would not be sufficient to justify action.

Landholders in the Booberoi to Quandialla (B-Q) Transect area, located in central west NSW, have been concerned about an emerging dryland salinity problem since the late 1990�s (Wooldridge 2002, pers. comm. Muller 2002, pers. comm.) with borehole information and electromagnetic induction investigations supporting anecdotal observations. The presence of indicator vegetation, waterlogging of soils and salinisation of land are becoming increasingly prevalent, with two well-documented sites including �Strathairlie� near Quandialla, and �Back Creek� near West Wyalong. The B-Q Transect area lies within the Bland Creek Catchment, a broad open plain of subdued topography and restricted drainage receiving sediments from elevated rises located to the west, south and east. Significant deposits of transported alluvial materials have in-filled the catchment to depths in excess of 160 m and have posed a particular impediment to regional-scale mineral exploration. Stream flow across the alluvial plains and low angle alluvial fans is intermittent with most of the flow being diverted into groundwater storage or lost to evaporation. Rarely do streams flow into Lake Cowal to the north. A partial electromagnetic (EM) induction survey coupled with a long term bore and piezometer network monitoring program have been implemented by the Department of Infrastructure, Planning and Natural Resources (DIPNR � formerly Department of Land and Water Conservation) Central West NSW Salt Group. These programs allow for initial, broad-scale evaluation of the magnitude and spatial distribution of the salinity problem but fail to pinpoint remaining sites at risk as well as the mechanisms of salt emplacement. As part of an approach to assist with hazard mitigation and land management, two regolith-landform maps are being compiled using 1:20,000 scales in the Back Creek and Quandialla areas. A third, more regional regolith-landform map at 1:50,000 scale (Holzapfel & Moore 2003a, b & c) provides context for the more detailed mapping areas. The new regolith-landform maps will aid in interpretation of existing geophysical techniques, help piece together the three-dimensional characteristics of the Bland Creek catchment, aid in the development of a shallow fluid flow and palaeotopographic model and assist land managers in formulating land management units (LMU�s). The three-dimensional integration of regolith-landform mapping, electromagnetic studies, bore information and other geophysical methods is critical in determining the interaction, distribution and movement of groundwater in the Bland Creek Catchment as buried palaeochannels represent preferred fluid pathways. The distribution of these palaeochannels has implications for future dryland salinity outbreaks, the remediation of current outbreaks and mineral exploration closer to the well-known Wyalong Goldfield (Lawrie et al., 1999). The western quarter of the B-Q Transect area partially overlaps with the recently completed GILMORE Project (Lawrie et al., 2003a,b & c), a multi-disciplinary study, coordinated by Geoscience Australia (GA) and the Bureau of Rural Sciences (BRS). Regolith-landform information in addition to gamma-ray spectrometry, magnetics, airborne electromagnetics and a digital elevation model acquired by the GILMORE Project have been incorporated into regolith-landform maps over the B-Q Transect. The incorporation of these datasets has helped not only extend the usefulness of the GILMORE Project data but provide a consistent, regolith-landform coverage for the broader Bland Creek Catchment. Regolith-landform mapping has been successful in highlighting major recharge zones for local and intermediate flow systems. The mechanisms for dryland salinity at two well-known sites have also been determined. Increasing salt stores are occurring through evaporation of intermittent floodwaters sourced from floodplains, back plains and broad meandering existing creek systems and recharging partially exposed palaeochannels intersecting the surface. Due to the shallow nature of these partially exposed palaeochannels, evaporation further concentrates the salt load in the soil profile. It is unknown if mapped shallow palaeochannels further away from current drainage systems are affected by rising salt loads. Regolith-landform mapping highlights two additional risk factors common to the 1:50,000 and 1:20,000 scale B-Q Transect mapping areas including widespread waterlogging of soils and wind erosion. Due to the subdued topography, features such as gilgai, fences and roads are having an effect on drainage modification. Wind erosion was also observed to play a major role within the B-Q Transect with significant loss of topsoil creating hardened clay surfaces resistant to water infiltration and significant redistributed deposits of aeolian materials. Interpretation of regolith-landform mapping against geophysical datasets and drill hole data show considerable lateral and vertical variation of regolith units. This variation of regolith distribution with depth does not reduce the effectiveness of using regolithlandform mapping as a valued management tool. The subdued relief coupled with the complex interplay between recharge zones, discharge zones and surficial drainage networks over the B-Q Transect still requires a detailed knowledge of surface regolithlandform characteristics whilst reinforcing the need for a multidisciplinary approach to gain a 3D perspective. Catchment analysis has been performed on drainage systems within the Bland Creek Catchment and has helped explain the strong effect different catchments have had on sediment supply to the Bland Basin. Catchment analysis results have been used in basic calculations of salt loads in the Bland Creek Catchment. An estimated 18,780 Tonnes/yr of salt enter the Bland Creek catchment and as stream flow out of the Bland Creek Catchment is intermittent, salt stores are increasing in the upper margins of the soil profile and groundwater reserves. Reconstruction of the palaeotopography of the B-Q Transect has been made possible using a mutli-disciplinary approach incorporating information from regolith-landform mapping, drill hole information, gamma-ray spectrometry and GILMORE Project datasets. The production of large-scale regolith-landform mapping, the development of a shallow fluid flow model and reconstruction of palaeotopography builds on and contributes to knowledge of the Bland Creek Catchment allowing for detailed farmscale and paddock-scale land management decisions.

[Truncated abstract] A functional ecosystem is increasingly being recognised as a requirement for health and well being of resident human populations. Clearing of native vegetation for agriculture has left 1.047 million hectares of south-west Western Australia affected by a severe form of environmental degradation, dryland salinity, characterised by secondary soil salinisation and waterlogging. This area may expand by a further 1.7-3.4 million hectares if current trends continue. Ecosystems in saline affected regions display many of the classic characteristics of Ecosystem Distress Syndrome (EDS). One outcome of EDS that has not yet been investigated in relation to dryland salinity is adverse human health implications. This thesis focuses on one such potential adverse health outcome: increased incidence of Ross River virus (RRV), the most common mosquito-borne disease in Australia. Spatial analysis of RRV notifications did not reveal a significant association with dryland salinity. To overcome inherent limitations with notification data, serological RRV antibody prevalence was also investigated, and again no significant association with dryland salinity was detected. However, the spatial scale imposed limited the sensitivity of both studies. ... This thesis represents the first attempt to prospectively investigate the influence of secondary soil salinity on mosquito-borne disease by combining entomological, environmental and epidemiological data. The evidence collected indicates that RRV disease incidence is not currently a significant population health priority in areas affected by dryland salinity despite the dominant presence of Ae. camptorhynchus. Potential limiting factors include; local climatic impact on the seasonal mosquito population dynamics; vertebrate host distribution and feeding behaviour of Ae. camptorhynchus; and the scarce and uneven human population distribution across the region. However, the potential for increased disease risk in dryland salinity affected areas to become apparent in the future cannot be discounted, particularly in light of the increasing extent predicted to develop over coming decades before any benefits of amelioration strategies are observed. Finally, it is important to note that both dryland salinity and salinity induced by irrigation are important forms of environmental degradation in arid and semi-arid worldwide, with a total population of over 400 million people. Potential health risks will of course vary widely across different regions depending on a range of factors specific to the local region and the complex interactions between them. It is therefore not possible to make broad generalisations. The need is highlighted for similar research in other regions and it is contended that an ecosystem health framework provides the necessary basis for such investigations.

Dryland-salinity management options aim to positively influence the adverse human-induced processes which lead to salinisation of top-soil. Specifically, the processes causing dryland-salinity are rising saline groundwater table and soil erosion. In the Avon region of Western Australia, the management options are evaluated solely on the basis of their efficiency in lowering groundwater tables. However, recently the need to take into account also their wider impact on the ecosystems' resilience has been recognised as well. Nevertheless, the tool to assess these impacts is missing. The aim of this thesis is to synthesise the missing tool from existing ecosystem services-based land-use evaluation frameworks, which would fit the environmental issue, regional socio-economic demands and the existing dryland salinity management options' efficiency evaluation framework. The thesis builds on secondary data and describes (i) the environmental issue of dryland salinity in Australia, (ii) the dryland salinity-environmental, economic, social and political environments of the Avon region, and (iii) five chosen evaluation frameworks which assess the impact of land-use on ecosystem resilience. The proposed optimal framework for the Avon region is then a combination of two existent frameworks: (i) ecosystem resilience evaluation framework & (ii) the ecosystem services economic valuation framework. Where the inputs of the proposed optimal framework are: (i) soil properties, (ii) external natural and anthropogenic drivers and (iii) beneficiaries; the transfer phase is represented by the soil processes; and the output of the framework are (i) ecosystem services and (ii) their economically valued benefits.

The first objective of the research was to investigate whether major geological faults had an impact on the development of dryland salinity, and what mechanism was the cause of the phenomenon. The second objective was to investigate revegetation treatments that would prevent land salinisation, and the effect of faults on the treatments’ impact. Investigation of three groups of catchments in the western wheatbelt. Western Australia, showed ten times more dryland salinity in the catchment underlain by a major fault than in the paired unfaulted catchment(s). Geomorphometric statistics show that catchments within each group are similar. There was no correlation between the degree of clearing for agriculture and the extent of dryland salinity. Detailed investigation of one group showed that there were no differences in salt store or regolith thickness between the faulted catchment and the adjacent unfaulted catchment. However, the mean hydraulic conductivity of boreholes within the fault zone, identified from an aeromagnetic survey, was five times higher than for boreholes outside the zone. That the mechanism underlying the association between the faults and dryland salinity is higher hydraulic conductivity inside the fault zone is supported by the flat piezometric surface in the faulted valley, and the continuous base flow in the faulted catchment, whilst the other catchments only flowed in response to winter rainfall. Computer modelling showed that 40% of the cleared area of the catchments would become saline if nothing is done. Modelling of revegetation treatments showed that replacing annual pasture with deep-rooted perennial pasture, or native vegetation, prevented the onset of dryland salinity. However, tree belts (alley fanning) left 15% of the cleared area saline. With the fault 50% more tree rows were required than predicted without the fault. A way of preparing a hydraulic conductivity map for use in computer modelling by interpretation of airborne geophysical data and borehole hydraulic conductivity testing is proposed.

This thesis demonstrates the use of geophysics to identify the hydrogeological structures and mechanisms responsible for the salinisation of land and water in three different case studies. In addition, it demonstrates the critical importance of the interpreted information products being relevant to the land managers and the management tools and strategies available to them. Three case studies are examined. The common requirement for each study area was the acquisition of detailed sub-surface information on the location of hydrogeological features that could not be interpreted from surface observations or obtained from isolated drill holes. The spatial coverage of the geophysical data is shown to be critical to the quality of location information produced. The interpretation of these data and presentation of information products in terms of the current management tools available to land managers are shown to be essential for successful and cost effective adoption.At Broomehill, the geophysical and other data were interpreted to produce information products that indicated the location of salt stores, sources of water, mechanisms that brought water and salt together in the landscape and mechanisms that brought saline groundwater to the surface. Using these information products, the spatial plan took the form of a farm plan that clearly mapped the location and design of surface water management earthworks, areas of revegetation, water storages, roads and fences such that the salinising processes in each paddock were directly impacted through the considered location of the proposed works. One such plan at Broomehill was promptly implemented in 1996 and the results have been monitored since that time. The farm plan is shown to be more cost effective than comparable farm plans on nearby properties that did not use information from geophysics.At Tammin, ground geophysical surveys (gravity and time domain electromagnetics) were used to identify the location of sedimentary fill in a buried inset valley. This was to provide information on which to base the siting of a production bore such that it would intersect hydrologically transmissive sediments. This bore was used to test the effectiveness of groundwater pumping to lower the watertable and recover agricultural land from salinity.The bore failed to pump an adequate volume of water and the groundwater pumping aspect of the trial was considered a failure. However, the value of this case study lies in observation of the characteristics of the geophysical information collected.The geophysical data were collected along four transects 0.8 km to 2.0 km apart. The processed geophysical data revealed cross-section profiles of the buried valley and the production bore was located on the transect that showed the steepest “V” profile. Given only four transects of information and the difficulty of interpolating over up to 2 km between them, this choice is understandable. The failure of the interpretation of the geophysical transect data to locate a suitable bore site calls into question the usefulness of geophysical survey transects up to 2 km apart. The geophysical information (although it was cheaper) was not much better than having four transects of closely spaced bores. It failed to adequately reveal the hydrogeological architecture of the study area. This case study revealed the importance of survey design and scope to ensure that the data are suitable to produce interpreted information products that are suitable for the purpose.A helicopter-borne, time domain electromagnetic survey was flown over the Lake Warden Wetlands near Esperance. The data were processed and interpreted to reveal potential groundwater flow paths in the main aquifers underlying the wetlands. This information, along with salt storage distribution maps derived from the conductivity product, was provided to the Department of Environment and Conservation (DEC) in the form of the maps shown in this thesis. This information enabled the DEC to formulate a catchment management strategy that focussed on the eastern sub-catchments of Bandy Creek and Neridup Creek as the main sources of saline groundwater. Surface water management plans prioritised diversion of waters contaminated by discharging saline groundwater and could be designed without active discharge occurring at the time. Prior to this survey, the DEC and South Coast Natural Resource Management were promoting generic management strategies, such as revegetation to reduce groundwater recharge, over the whole catchment area.The information products developed in this study enabled the DEC and community to understand mechanisms causing high water tables and salinisation in the wetlands and consequently, to be much more targeted and effective in their investment of limited land conservation funding.In all these case studies, the use of geophysics was essential to identify the hydrogeological architecture and mechanisms responsible for the salinisation of land and water. Furthermore, the interpretation of the data and design of information products is critical as to whether the information is successfully acted upon. The interpretation of the data and design of information products based on location of aquifers and other geological structures is critical to adoption by land managers and the impact and effectiveness of the actions taken.

Over the past thirty years, price relativities and technological development have motivated an increase in the area of land allocated to cropping, as opposed to pasture production, throughout the central wheat belt of Western Australia. Nevertheless, reducing the proportion of pasture in these rotations has challenged the future productivity of farming systems in this area. First, the frequent application of selective herbicides for weed control in extended cropping rotations has promoted the development of herbicide resistance in a number of major agricultural weeds. Second, the primary use of annual plants has promoted the development of soil salinisation by allowing a significant proportion of rainfall to recharge saline water tables. The inclusion of perennial pasture phases between extended periods of cropping may mitigate or delay these constraints to production through (a) allowing the use of costeffective forms of non-selective weed control, and (b) through creating a buffer of dry soil that absorbs leakage occurring beneath subsequent crops. This study consequently explores the value of including perennial pasture phases in dryland agricultural systems in the eastern-central wheat belt of Western Australia, accounting for benefits related to herbicide resistance and water table management. A novel computational algorithm for the solution of multiple-phase optimal control problems is developed and used to conduct a conceptual analysis of the value of lucerne (Medicago sativa L.) pasture for managing annual ryegrass (Lolium rigidum Gaudin), the primary weed in wheat belt cropping systems. The competitiveness and fecundity of annual ryegrass provide strong economic incentives to maintain a low weed population, irrespective of herbicide-resistance status. Consequently, the ineffectiveness of selective herbicides primarily reduces the profitability of cropping by motivating the adoption of more costly non-selective forms of weed control. The inclusion of lucerne in land-use rotations is only optimal in the presence of severe herbicide resistance given (a) the low efficiency of alternative weed-management practices available during the pasture phase, relative to selective-herbicide application; (b) the significant cost of establishing this perennial pasture; and (c) the high relative profitability of cereal production in the absence of resistance. The value of lucerne, relative to annual pastures, for weed management is explored in greater detail through the use of compressed annealing to optimise a sophisticated simulation model. The profitability of candidate rotations is also manipulated to account for the long-term production losses accruing to the recharge of saline groundwaters that occurs beneath them. Sequences incorporating lucerne are only more profitable than those that include annual pasture at the standard set of parameter values if (a) annual ryegrass is resistant to all selective herbicides, (b) the water table is so shallow (approximately less than 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, or (c) sheep production is highly profitable. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost. Consistent with intuition, these benefits are reinforced by lower discount rates and higher rates of leakage occurring beneath annual-based systems. Formulation of an effective communication strategy to report these results to producers is justified given the complexity involved in determining the true magnitude of these intertemporal benefits through alternative means, such as field trials.

Dryland salinity occurs extensively throughout the Spicers Creek Catchment in central west New South Wales, Australia. The extent of dryland salinity in the Spicers Creek Catchment has severely altered the landscape, having major environmental implication. Large area of the catchments has experienced soil erosion resulting from the saline groundwater in the surface soil causing the destruction of clay and soil structure. The objective of this study was to use seismic refraction methods to map in detail a shear zone, which was associated with an area of major dryland salination. In particular, both the width of shear zone and the rock fabric within it were to be mapped with two both compressional (P) and shear (S) waves using a three-dimensional (3D) array of three- component (3C) receivers. The seismic data was recorded across a shear zone which is associated with salination in the Spicers Creek Catchment using the Australian National Seismic Imaging Resources (ANSIR) 360-trace system. Three-component (3C) geophones were used to record shear waves as well as compressional wave. An IVI minivibrator T-15000 was used as the main source of energy for the seismic survey. The results of the three-dimensional three-component seismic refraction surveys at the Spicers Creek Catchment show that the shear zone exhibit the seismic geophysical anomaly of a shear zone, existing as a narrow region with low seismic velocities and increased depth of weathering. A detailed analysis of the refractor seismic velocities and amplitude show a number of linear features parallel to and cross-cutting the shear zone. Linear features cut the shear zones at each site. They have been interpreted as a series of recent faults which act as discharge zone bringing saline groundwater to the surface.

Thesis (PhD)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Bugan, R.D.H. Modelling and regulating hydrosalinity dynamics in the Sandspruit River catchment (Western Cape). PhD dissertation, Stellenbosch University. The presence and impacts of dryland salinity are increasingly become evident in the semi-arid Western Cape. This may have serious consequences for a region which has already been classified as water scarce. This dissertation is a first attempt at providing a methodology for regulating the hydrosalinity dynamics in a catchment affected by dryland salinity, i.e. the Sandspruit catchment, through the use of a distributed hydrological model. It documents the entire hydrological modelling process, i.e. the progression from data collection to model application. A review of previous work has revealed that salinisation is a result of land use change from perennial indigenous deep rooted vegetation to annual shallow rooted cropping systems. This has altered the water and salinity dynamics in the catchment resulting in the mobilisation of stored salts and subsequently the salinisation of land and water resources. The identification of dryland salinity mitigation measures requires thorough knowledge of the water and salinity dynamics of the study area. A detailed water balance and conceptual flow model was calculated and developed for the Sandspruit catchment. The annual streamflow and precipitation ranged between 0.026 mm a-1 - 75.401 mm a-1 and 351 and 655 mm a-1 (averaging at 473 mm a- 1), respectively. Evapotranspiration was found to be the dominant component of the water balance, as it comprises, on average, 94% of precipitation. Streamflow is interpreted to be driven by quickflow, i.e. overland flow and interflow, with minimal contribution from groundwater. Quantification of the catchment scale salinity fluxes indicated the Sandspruit catchment is in a state of salt depletion, i.e. salt output exceeds salt input. The total salt input to and output from the Sandspruit catchment ranged between 2 261 - 3 684 t Catchment-1 and 12 671 t a-1 - 21 409 t a-1, respectively. Knowledge of the spatial distribution of salt storage is essential for identifying target areas to implement mitigation measures. A correlation between the salinity of sediment samples collected during borehole drilling and the groundwater EC (r2 = 0.75) allowed for the point data of salt storage to be interpolated. Interpolated salt storage ranged between 3 t ha-1 and 674 t ha-1, exhibiting generally increasing storage with decreasing ground elevation. The quantified water and salinity fluxes formed the basis for the application of the JAMS/J2000-NaCl hydrological model in the Sandspruit catchment. The model was able to adequately simulate the hydrology of the catchment, exhibiting a daily Nash-Sutcliffe Efficiency of 0.61. The simulated and observed salt outputs exhibited discrepancies at daily scale but were comparable at an annual scale. Recharge control, through the introduction of deep rooted perennial species, has been identified as the dominant measure to mitigate the impacts of dryland salinity. The effect of various land use change scenarios on the catchment hydrosalinity balance was evaluated with the JAMS/J2000-NaCl model. The simulated hydrosalinity balance exhibited sensitivity to land use change, with rooting depth being the main factor, and the spatial distribution of vegetation. Revegetation with Mixed forests, Evergreen forests and Range Brush were most effective in reducing salt leaching, when the “salinity hotspots” were targeted for re-vegetation (Scenario 3). This re-vegetation strategy resulted in an almost 50% reduction in catchment salt output. Overall, the results of the scenario simulations provided evidence for the consideration of re-vegetation strategies as a dryland salinity mitigation measure in the Sandspruit catchment. The importance of a targeted approach was also highlighted, i.e. mitigation measures should be implemented in areas which exhibit a high salt storage.
AFRIKAANSE OPSOMMING: Die teenwoordigheid en impak van droëland versouting word duideliker in die halfdor Wes-Kaap. Dit kan ernstige gevolge inhou vir die streek wat reeds as ‘n waterskaars area geklassifiseer is. Hierdie verhandeling is ‘n poging om ‘n metode vir die regulering van waterversoutingsdinamiek in ‘n opvangsgebied wat deur verbrakking van grond geaffekteer is, i.e. die Sandspruit opvangsgebied, te bepaal deur gebruik te maak van ‘n verspreide hidrologiese model. Dit dokumenteer die volledige hidrologiese modeleringsproses, i.e. vanaf die versameling van data tot die aanwending van die model. ‘n Oorsig van vorige studies bevestig dat versouting ‘n gevolg is van die verandering vanaf meerjarige inheemse plantegroei met diep wortelstelsels tot die verbouing van gewasse met vlak wortelstelsels. Dit het ‘n verandering in die water en versoutingsdinamiek in die opvangsgebied tot gevolg gehad in soverre dat dit die mobilisering van versamelde soute en gevolglike versouting van die grond en waterbronne tot gevolg gehad het. Die identifikasie van maatreëls om droëland versouting te verminder, vereis ‘n deeglike kennis van die water- en versoutingsdinamiek van die studie gebied. ‘n Gedetailleerde waterbalans en konseptuele vloeimodel was bereken vir die Sandspruit opvangsgebied. Die jaarlikse stroomvloei en neerslag varieer tussen 0.026 - 75.401 mm a-1 en 351 - 655 mm a-1 (gemiddeld 473 mm a-1), onderskeidelik. Dit is bevind dat evapotranspirasie die dominante komponent is van die waterbalans, aangesien dit 94% uitmaak van die neerslag. Stroomvloei word aangedryf deur snelvloei, i.e oppervlakvloei en deurvloei met minimale bydrae van grondwater. Die omvang van die opvangsgebied se soutgehalte het aangedui dat die Sandspruit opvangsgebied tans ‘n toestand van soutvermindering ondervind, i.e. sout invloei word oorskrei deur sout uitvloei. Die totale sout in- en uitvloei in die Sandspruit opvangsgebied het gewissel tussen 2 261 - 3 684 t Opvangsgebied-1 en 12 671 - 21 409 t a-1 onderskeidelik. Kennis van die ruimtelike verspreiding van opbou van soute in die grond is belangrik om areas te identifiseer vir die toepassing van voorsorgmaatreëls. ‘n Korrelasie tussen die soutinhoud van sediment monsters wat versamel is tydens die boor van boorgate en die grondwater EC (r2 = 0.75) het die interpolasie van puntdata waar sout aansamel toegelaat. Hierdie interpolasie van sout aansameling het gewissel tussen 3 t ha-1 and 674 t ha-1 en bewys ‘n algemeen verhoogde opbou met vermindering in grond elevasie. Die hoeveelheidsbepaling van water en die versoutings roetering vorm die basis vir die aanwending van die JAMS/J2000-NaCl hidrologiese model in die Sandspruit opvangsgebied. Die model het ‘n geskikte simulasie van die hidrologie van die opvangsgebied geimplimenteer, en het ‘n daaglikse Nash-Sutcliffe Efficiency van 0.61 getoon. Die gesimuleerde en waargenome sout afvoer het teenstrydighede getoon t.o.v daaglike metings maar was verenigbaar op ‘n jaarlikse skaal. Aanvullingsbeheer deur die aanplanting van meerjarige spesies met diep wortelstelsels is geidentifiseer as ‘n oorwegende maatreël om die impak van verbrakking van grond teë te werk. Die effek van verskeie veranderde grondgebuike op die balans van die opvangsgebied se hidro-soutgehalte is geëvalueer met die JAMS/J2000-NaCl model. Die balans van gesimuleerde hidro-saliniteit het ‘n sensitiwiteit t.o.v veranderde grondgebruik getoon, met die diepte van wortelstels as die hoof faktor, asook die ruimtelike verspreiding van plantegroei. Hervestiging van verskeie tipes bome, meerjarige bome en “Range Brush” was die effektiefste t.o.v die vermindering in sout uitloging waar die soutgraad konsentrasie areas ge-oormerk was vir hervestiging van plantegroei (Scenario 3). Die strategie van hervestinging het ‘n afname van 50% in versouting in die opvangsgebied getoon. In die geheel het die resultate van die simulasies genoegsame bewys gelewer dat ‘n strategie van hervestiging en groei as ‘n voorsorg maatreël kan dien om droëland versouting in die Sandspruit opvangsgebied teen te werk. Die belangrikeid daarvan om ‘n geteikende benadering te volg is benadruk, i.e. voorsorg maatreëls kan toegepas word in areas met hoë soutgehalte.

Dryland salinity has become a major environmental problem in Australia through changes in land management incurred since European settlement. Given appropriate conditions of land management and clin1ate, salinisation follows the advent of discharge areas which arise through rises in groundwater level and/or impediments to groundwater flow. Impediments may be structures such as dams, roads and railway embankments but can also occur naturally through geological features. Geological structures such as dykes, faults and contact zones may be impediments to groundwater flow as can changes to hydraulic conductivity through changes in the permeability of rocks and soils. Geological factors have been incorporated into a predictive model to identify areas at risk to salinisation. The model is a Decision Tree Analysis run via the Knowledge SEEKER computer program. Results from this modelling exercise are comparable with other models based on surface and near-surface flow and topographic indices but suffer from being site specific. The study highlights the need for development of improved methods of mapping subsurface features and for widespread changes to the current system of land management.

Dryland salinity is claimed to be potentially the nation's greatest environmental problem. In NSW, it occurs mainly in the upland areas in the south-east of the State. This region is part of the Murray-Darling Basin and has the potential to contribute to its worsening salinity. This thesis examines the nature of its occurrence in this area, and the implications for its remediation. There are two opposing models of the causes of dryland salinity. The first, a more long held view, is that salinisation is localised, restricted to particular soils and landforms, restricted in its spread, episodic in its development, and responsive to mitigation measures within its own local catchment or recharge area. A more recent view is that the problem is one of regional dimension, driven by rising regional groundwater systems, progressive in its spread, and having the potential to degrade large areas with serious off-site consequences, principally as a result of increasing stream salinity. Here, the genesis of the problem is seen as the widespread clearing of timber in regional recharge areas following European settlement. The chief remedy proposed is to restore tree cover; with up to 50 percent of the higher rainfall zone in the Murray-Darling Basin being replanted to trees. The opposing models differ greatly in their conception of the magnitude of the problem, and its potential for expansion. They present widely different management and policy options for its mitigation. The social and economic impacts of any programs proposed similarly differ. This thesis uses aerial photography, site inspections, and farmer interviews to trace the development of dryland salinity in the south-east region of NSW. The findings are compared with the expectations from the two models. It was found that dryland salinity across the region was not a recent phenomenon. One site developed before 1900 and there were episodic periods of expansion in the 1930s and 1950s to 1960s, with most sites reaching their maximum extent by the early 1970s. Most sites occurred as isolated outbreaks, associated with local landscape features and soil types. Their development appeared to be closely related to changes in rainfall patterns, to past land use and management of the affected sites themselves, and their local recharge areas. There was no evidence of continued expansion in the last two decades, and little evidence of any progressive spread, either spatially or temporally, as projected from regional watertable modeling. However the conditions that predispose lands to dryland salinity still exist, and there could be an extension of the problem in the future. In a limited number of cases, rehabilitation of former saline areas has been achieved at the local property level. Here the landholders had broader objectives than solely controlling salinity. Their primary objectives were to develop more productive and sustainable farming systems. The improved practices introduced also overcame other associated land degradation problems. These measures, at a local recharge level, were effective within a reasonably short time. Although long term regional programs may be needed, the study showed that many of the incidences of local salinity development appear to be associated with local factors. Successful treatment at a local property level appears to confirm this. Such treatments have the potential to reduce salt flushes from farm lands to streams. The success of these treatments is not consistent with the regional groundwater model. Tree planting on the scale proposed from this model, may not be necessary; and the development and adoption of more sustainable farming systems widely across landscapes may largely redress the situation. These systems in themselves would include more trees. This approach would not require the huge capital investment necessary with tree or engineering solutions. The necessary treatments would be more within the reach of individual landholders, and would be much less disruptive to the existing agricultural infrastructure and community life than the massive tree planting programs proposed, and may ensure a better allocation of resources overall. More support at the local community level should also be achievable. Dryland salinity is a symptom as well as the result of unsustainable land use and management. It is concluded that reduction in the hazard does not depend on a singular approach such as tree planting, but principally on the development and adoption of more sustainable and productive farming systems. Technology is being developed that could provide the basis for such systems. Means also must be developed to foster their wider adoption.

Bibliography: p. 161-185. The main aim of this project was to establish whether or not interception belts can be expected to transpire sufficient volumes of water to be considered a feasible option for controlling rising groundwater. (conclusion)

Airborne hyperspectral imagery has the potential to overcome the spectral and spatial resolution limitations of multispectral satellite imagery for monitoring salinity at both regional and farm scales. In particular, saline areas that have good cover of salt tolerant plants are difficult to map with multispectral satellite imagery. Hyperspectral imagery may provide a more reliable salinity mapping method because of its potential to discriminate halophytic plant cover from non - halophytes. HyMap and CASI airborne imagery ( at 3m ground resolution ) and Hyperion satellite imagery ( at 30 resolution ) were acquired over a 140 sq km dryland agricultural area in South Australia, which exhibits severe symptoms of salinity, including extensive patches of the perennial halophytic shrub samphire ( Halosarcia pergranulata ), sea barley grass ( Hordeum marinum ) and salt encrusted pans. The HyMap and Hyperion imagery were acquired in the dry season ( March and February respectively ) to maximise soil and perennial vegetation mapping. The optimum time of year to map sea barley grass, an annual species, was investigated through spectral discrimination analysis. Multiple reflectance spectra were collected of sea barley grass and other annual grasses with an ASD Fieldspec Pro spectrometer during the September spring flush and in November during late senescence. Comparing spectra of different species in November attempted to capture the spectral differences between the late senescing sea barley grass and other annual grasses. Broad NIR and SWIR regions were identified where sea barley grass differs significantly from other species in November during late senescence. The sea barley grass was therefore shown to have the potential to be discriminated and mapped with hyperspectral imagery at this time and as a result the CASI survey was commission for November. Other salinity symptoms were characterised by collecting single field and laboratory spectra for comparison to image derived spectra in order to provide certainty about the landscape components that were to be mapped. Endmembers spectra associated with saltpans and samphire patches were extracted from the imagery using automated endmember generation procedures or selected regions of interest and used in subsequent partial unmixing. Spectral subsets were evaluated for their ability to optimise salinity maps. The saltpan spectra contained absorption features consistent with montmorillonite and gypsum. A single gypsum endmember from one image strip successfully mapped saltpans across multiple images strips using the 1750 nm absorption feature as the input to matched filter unmixing. The individual spectra of green and red samphire are dominated by photosynthetic vegetation characteristics. The spectra of green samphire, often seen with red tips, exhibit peaks in both green and red wavebands whereas the red samphire spectra only contain a significant reflectance peak in the visible red wavelength region. For samphire, Mixture Tuned Matched Filtering using image spectra, containing all wavelength regions, from known samphire patches produced the most satisfactory mapping. Output salinity maps were validated at over 100 random sites. The HyMap salinity maps produced the most accurate results compared to CASI and Hyperion. HyMap successfully mapped highly saline areas with a good cover of samphire vegetation at Point Sturt without the use of multitemporal imagery or ancillary data such as topography or PIRSA soil attribute maps. CASI and Hyperion successfully mapped saltpan, however, their samphire maps showed a poor agreement with field data. These results suggest that perennial vegetation mapping requires all three visible, NIR and SWIR wavelength regions because the SWIR region contains important spectral properties related to halophytic adaptations. Furthermore, the unconvincing results of the CASI sea barley grass maps suggests that the optimal sensor for mapping both soil and vegetation salinity symptoms are airborne sensors with high spatial and spectral resolution, that incorporate the 450 to 1450 nm wavelength range, such as HyMap. This study has demonstrated that readily available software and image analysis techniques are capable of mapping indicators of varying levels of salinity. With the ability to map symptoms across multiple image strips, airborne hyperspectral imagery has the potential for mapping larger areas covering sizeable dryland agriculture catchments, closer in extent to single satellite images. This study has illustrated the advantage of the hyperspectral imagery over traditional soil mapping based on aerial photography interpretation such as the NLWRA Salinity 2000 and the PIRSA soil landscape unit maps. The HyMap salinity maps not only improved mapping of saline areas covered with samphire but also provided salinity maps that varied spatially within saline polygons.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2006.

Airborne hyperspectral imagery has the potential to overcome the spectral and spatial resolution limitations of multispectral satellite imagery for monitoring salinity at both regional and farm scales. In particular, saline areas that have good cover of salt tolerant plants are difficult to map with multispectral satellite imagery. Hyperspectral imagery may provide a more reliable salinity mapping method because of its potential to discriminate halophytic plant cover from non - halophytes. HyMap and CASI airborne imagery ( at 3m ground resolution ) and Hyperion satellite imagery ( at 30 resolution ) were acquired over a 140 sq km dryland agricultural area in South Australia, which exhibits severe symptoms of salinity, including extensive patches of the perennial halophytic shrub samphire ( Halosarcia pergranulata ), sea barley grass ( Hordeum marinum ) and salt encrusted pans. The HyMap and Hyperion imagery were acquired in the dry season ( March and February respectively ) to maximise soil and perennial vegetation mapping. The optimum time of year to map sea barley grass, an annual species, was investigated through spectral discrimination analysis. Multiple reflectance spectra were collected of sea barley grass and other annual grasses with an ASD Fieldspec Pro spectrometer during the September spring flush and in November during late senescence. Comparing spectra of different species in November attempted to capture the spectral differences between the late senescing sea barley grass and other annual grasses. Broad NIR and SWIR regions were identified where sea barley grass differs significantly from other species in November during late senescence. The sea barley grass was therefore shown to have the potential to be discriminated and mapped with hyperspectral imagery at this time and as a result the CASI survey was commission for November. Other salinity symptoms were characterised by collecting single field and laboratory spectra for comparison to image derived spectra in order to provide certainty about the landscape components that were to be mapped. Endmembers spectra associated with saltpans and samphire patches were extracted from the imagery using automated endmember generation procedures or selected regions of interest and used in subsequent partial unmixing. Spectral subsets were evaluated for their ability to optimise salinity maps. The saltpan spectra contained absorption features consistent with montmorillonite and gypsum. A single gypsum endmember from one image strip successfully mapped saltpans across multiple images strips using the 1750 nm absorption feature as the input to matched filter unmixing. The individual spectra of green and red samphire are dominated by photosynthetic vegetation characteristics. The spectra of green samphire, often seen with red tips, exhibit peaks in both green and red wavebands whereas the red samphire spectra only contain a significant reflectance peak in the visible red wavelength region. For samphire, Mixture Tuned Matched Filtering using image spectra, containing all wavelength regions, from known samphire patches produced the most satisfactory mapping. Output salinity maps were validated at over 100 random sites. The HyMap salinity maps produced the most accurate results compared to CASI and Hyperion. HyMap successfully mapped highly saline areas with a good cover of samphire vegetation at Point Sturt without the use of multitemporal imagery or ancillary data such as topography or PIRSA soil attribute maps. CASI and Hyperion successfully mapped saltpan, however, their samphire maps showed a poor agreement with field data. These results suggest that perennial vegetation mapping requires all three visible, NIR and SWIR wavelength regions because the SWIR region contains important spectral properties related to halophytic adaptations. Furthermore, the unconvincing results of the CASI sea barley grass maps suggests that the optimal sensor for mapping both soil and vegetation salinity symptoms are airborne sensors with high spatial and spectral resolution, that incorporate the 450 to 1450 nm wavelength range, such as HyMap. This study has demonstrated that readily available software and image analysis techniques are capable of mapping indicators of varying levels of salinity. With the ability to map symptoms across multiple image strips, airborne hyperspectral imagery has the potential for mapping larger areas covering sizeable dryland agriculture catchments, closer in extent to single satellite images. This study has illustrated the advantage of the hyperspectral imagery over traditional soil mapping based on aerial photography interpretation such as the NLWRA Salinity 2000 and the PIRSA soil landscape unit maps. The HyMap salinity maps not only improved mapping of saline areas covered with samphire but also provided salinity maps that varied spatially within saline polygons.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2006.

Associated with the problems of rising groundwater levels and dryland salinity are the conflicting economic and environmental objectives which aim to maximise net revenue from agriculture whilst still conserving the ecological standards of the natural environment. From an economic perspective, the central objective of salinity management should be to obtain the socially optimum value of resource use (including conservation) over time. Economics can contribute to the resolution of natural resource conflicts, by concentrating specifically on the allocation of scarce resources among competing demands, and determining which actions are economic from a catchment perspective. From an environmental standpoint, it is important to ensure that the natural environment is conserved not only today, but also for future generations. Despite the importance of managing the natural resource base from both an environmental and economic perspective, numerical models, which simulate the spatial and temporal movement of saline groundwater, have not been used extensively in economic analyses. Consequently, the focus in this thesis, is on the economic-physical system modelling of dryland salinity, in Western Australia. A transient hydrogeological-economic model has been developed and applied to the North Stirling Land Conservation District, a severely salt-affected area located in south-west Western Australia, to assess the current and future impacts of varying a catchment's land use pattern on groundwater levels and agricultural production. Several alternative salinity management options which may be applied to the District have been simulated, including an agronomic practice and an agroforestry strategy. Results of the simulations show that the choice of alternative land uses that should be adopted in order to reduced losses in gross margins in an area affected by dryland salinity, will depend primarily upon the effects of the various crop, pasture and tree species planted on the dynamic and spatial variations in groundwater levels, and the relative economic returns of those species. The 1995 value of potential gross margin receipts over the nine-year period (1992 to 2000, inclusive) is expected to be $10 million. By maintaining current land use practices across the study area, groundwater levels are estimated to rise by 1 m and the opportunity cost of salinity, in terms of foregone agricultural production, is estimated to be almost $6.7 million over this period. By adopting a discharge zone planting (or agronomic) strategy, whereby salt-tolerant shrubs are established on saline areas th a t can no longer su s ta in traditional agricultural production, piezometric heads are estimated to decrease by 0.3 m over the same nine-year period and the opportunity cost of salinity is estimated to decline by $720,000 compared to the 'do-nothing' approach. Alternatively, if agroforestry techniques (in this case alley farming) are introduced to those areas within the NSLCD study area that currently support traditional crops and pastures, average piezometric heads at the end of the forecasting period (year 2000) are estimated to be 0.4 m lower than average heads predicted under the agronomic option (or 0 .7 m com pared to the do-nothing' approach). Gross margins are expected to be $790,000 higher under the agroforestry approach than if existing farming practices are maintained. However, unlike the alternative scenarios modelled in this study, the estimated gross margins are expected to increase over the forecasting period as the higher water-using trees planted throughout the study area cause groundwater levels to decline further. On a more general note, the modelling approach developed here is a generic one that can be successfully applied to many areas affected by salinity. Such models are beneficial as they provide additional information which helps the community, farmers, Landcare groups and the government make important decisions on how best to manage the agricultural and natural resources upon which we rely for productivity and environmental amenity.

Secondary dryland salinity in Australia has been a major environmental concern for a number of decades, yet aspects remain controversial. These include the processes which induce salinised soils, the environmental impacts of salinity, and the way in which it is mapped and managed. Dryland salinity has been almost universally attributed to rising saline groundwater caused by excess water accumulation in the landscape following European settlement and tree clearing. However, there is a body of evidence that instead suggests increased soil salinisation in SE Australia is attributable to localized surface water problems associated with soil and vegetation degradation. The ‘Rising Groundwater Model’ has been widely accepted as the paradigm for understanding, mapping and monitoring dryland salinity. However, little quantitative research has been undertaken to understand the mechanisms and processes that cause secondary dryland salinity in the uplands of south eastern Australia. Further, there is little research that demonstrates adverse impacts of secondary salinity on terrestrial endemic biota even though it is listed as a threatening process to biodiversity. This research tested the applicability of an alternative ‘Surface Water Model’ to explain outbreaks of salinity or soil surface degradation in this region. This research investigated the effects of the joint phenomenon of soil and vegetation degradation and elevated salinity levels on soil biotic and abiotic parameters. Field research was conducted at ten box/gum grassy woodland sites in the agricultural zone of the Southern Tablelands of NSW. A holistic suite of metrics, including soil physical, chemical, hydrological and biological attributes, were assessed in the field and laboratory; geophysical surveys (EM31/EM38) and various fauna and flora surveys were performed. Results indicated that degraded soil surfaces were generally small in area and localized. These surfaces had highly variable soil EC levels (often very low), and were associated with in situ synergistic factors related to in situ soil and vegetation degradation. Some surfaces had accumulated NaCl, but many also had other, both toxic and low cation and anion levels particularly reduced levels of Ca, Fe, N, SOM and SOC. Extreme pH levels and other soil physical, chemical and biological impacts were also common. It is concluded that elevated soil salinity levels are a symptom of soil and vegetation degradation, not the cause. It was found that the predominant water movement in these landscapes occurred as overland runoff and surficial lateral interflow above the clay-dominant B horizon. There was no biological, pedological, geophysical or hydrological evidence of groundwater being a major factor for elevated soil surface salinity levels. Evidence suggests that these degraded ecosystems are relatively stable but urgently require nutrient/SOM input. Many endemic fauna and flora species flourish at highly degraded and salinised sites; tolerating elevated and fluctuating salinity levels, at all life cycle stages, which may effectively increase the gamma biodiversity in these grassy woodlands. No evidence was found to suggest that biodiversity is suffering from rising saline groundwater or elevated soil salinity levels per se, or that elevated salinity levels favour exotic species. It is therefore problematical to directly link soil salinity per se with ecological stress, as many other synergistic factors are involved and are more significant for degraded soils. Management decisions based on reducing the soil surface evaporation potential on site is the most coherent approach. Management activities should focus on stock grazing exclusion, soil amelioration and revegetation activities using endemic species, rather than focusing on excess deep landscape water management with hybrids and exotic plants. The present use of AEM for mapping dryland salinity in upland environments is therefore questionable.

Bibliography: leaves 119-218.
xiv, 218 leaves : ill. (some col.), maps (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Salt Manager represents the software system developed by this thesis to implement an interactive land classification methodology. An Expert System (ES), a Geographic Information System (GIS), remotely sensed information and a relational database management system (RDBMS) have been utilised to construct the methodology.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geography, 1995

Bibliography: leaves 119-218.
xiv, 218 leaves : ill. (some col.), maps (some col.) ; 30 cm.
Salt Manager represents the software system developed by this thesis to implement an interactive land classification methodology. An Expert System (ES), a Geographic Information System (GIS), remotely sensed information and a relational database management system (RDBMS) have been utilised to construct the methodology.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geography, 1995

The East Barmoya and adjoining catchments in coastal central Queensland are suffering classic symptoms of dryland salinity, brought on by clearing of dry-rainforests in their upper catchments. The problem became manifest in the 1920-30s, expanded rapidly in the 1950s and has intermittently increased until the present, lagging some 20 to 30 years behind the period of large scale clearing in the catchment. Plant succession onto the new saline environment is considered, and a production system involving marine couch (Sporobolus virginicus) and swamp-oak (Casuarina glauca) is advocated. The role of soil mounding and mulching for the establishment of Casuarina glauca onto waterlogged, salinized land (water-table within 1 m of soil surface, surface soil EC1:5 0.0-0.1 m c. 10 dS.m -1) in Central Queensland was investigated in a factorial experiment involving two levels of soil mounding (0.05 and 0.15 m) and four mulch conditions (no mulch, hay, black and white plastic). Mounding was of little effect on plant survival, growth, soil pH or conductivity, however mulching greatly influenced these parameters, with the exception of soil pH. Plastic mulch is recommended over hay mulch. Installation of the plastic mulch was mechanized, involving cultivation of the soil to mix surface salts, mounding of soil into an M cross-section to harvest rain water to the seedling, and use of a commercial mulchlayer for plastic film installation. An established individual swamp-oak was found to use 8-11 L.d-1 of groundwater. Using a steady state model for the water-table depression due to water extraction from a well and assuming that the tree used only groundwater, the depression was calculated to be c. 1 m (steady state) for the low hydraulic conductivity soils (clays) that typify dryland salinity discharge sites. During a forty day period, the tree caused a water-table depression of 10 cm, relative to a reference point 10 m from the tree. Further, a diurnal oscillation of 1 cm occurred in the water-table under the tree. With water use by the single tree considered to be sufficient to cause localized inhibition of the unsaturated flow of groundwater to the soil surface, an estimation was made of the density of trees required to lower the water-table beyond the capillary fringe and thereby reverse the salinization process.