Hydrologic landscape regionalisation using deductive classification and random forests
- Authors: Brown, Stuart , Lester, Rebecca , Versace, Vincent , Fawcett, Jonathon , Laurenson, Laurie
- Date: 2014
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 9, no. 11 (2014), p. e112856
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- Description: Landscape classification and hydrological regionalisation studies are being increasingly used in ecohydrology to aid in the management and research of aquatic resources. We present a methodology for classifying hydrologic landscapes based on spatial environmental variables by employing non-parametric statistics and hybrid image classification. Our approach differed from previous classifications which have required the use of an a priori spatial unit (e.g. a catchment) which necessarily results in the loss of variability that is known to exist within those units. The use of a simple statistical approach to identify an appropriate number of classes eliminated the need for large amounts of post-hoc testing with different number of groups, or the selection and justification of an arbitrary number. Using statistical clustering, we identified 23 distinct groups within our training dataset. The use of a hybrid classification employing random forests extended this statistical clustering to an area of approximately 228,000 km2 of south-eastern Australia without the need to rely on catchments, landscape units or stream sections. This extension resulted in a highly accurate regionalisation at both 30-m and 2.5-km resolution, and a less-accurate 10-km classification that would be more appropriate for use at a continental scale. A smaller case study, of an area covering 27,000 km2, demonstrated that the method preserved the intra- and intercatchment variability that is known to exist in local hydrology, based on previous research. Preliminary analysis linking the regionalisation to streamflow indices is promising suggesting that the method could be used to predict streamflow behaviour in ungauged catchments. Our work therefore simplifies current classification frameworks that are becoming more popular in ecohydrology, while better retaining small-scale variability in hydrology, thus enabling future attempts to explain and visualise broad-scale hydrologic trends at the scale of catchments and continents.
Assessment of spatiotemporal varying relationships between rainfall, land cover and surface water area using geographically weighted regression
- Authors: Brown, Stuart , Versace, Vincent , Laurenson, Laurie , Ierodiaconou, Daniel , Fawcett, Jonathon , Salzman, Scott
- Date: 2012
- Type: Text , Journal article
- Relation: Environmental Modeling and Assessment Vol. 17, no. 3 (2012), p. 241-254
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- Description: Traditional regression techniques such as ordinary least squares (OLS) are often unable to accurately model spatially varying data and may ignore or hide local variations in model coefficients. A relatively new technique, geographically weighted regression (GWR) has been shown to greatly improve model performance compared to OLS in terms of higher R 2 and lower corrected Akaike information criterion (AIC C). GWR models have the potential to improve reliabilities of the identified relationships by reducing spatial autocorrelations and by accounting for local variations and spatial non-stationarity between dependent and independent variables. In this study, GWR was used to examine the relationship between land cover, rainfall and surface water habitat in 149 sub-catchments in a predominately agricultural region covering 2.6 million ha in southeast Australia. The application of the GWR models revealed that the relationships between land cover, rainfall and surface water habitat display significant spatial non-stationarity. GWR showed improvements over analogous OLS models in terms of higher R 2 and lower AIC C. The increased explanatory power of GWR was confirmed by the results of an approximate likelihood ratio test, which showed statistically significant improvements over analogous OLS models. The models suggest that the amount of surface water area in the landscape is related to anthropogenic drainage practices enhancing runoff to facilitate intensive agriculture and increased plantation forestry. However, with some key variables not present in our analysis, the strength of this relationship could not be qualified. GWR techniques have the potential to serve as a useful tool for environmental research and management across a broad range of scales for the investigation of spatially varying relationships. © 2011 Springer Science+Business Media B.V.
Salinity without rising watertables: salinity processes and risk assessment in south-west Victoria
- Authors: Dahlhaus, Peter , Fawcett, Jonathon
- Date: 2008
- Type: Text , Conference proceedings
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- Description: 2003009093
Hydropedology, geomorphology and groundwater processes hold the keys to land degradation - case studies in SW Victoria, Australia
- Authors: MacEwan, Richard , Dahlhaus, Peter , Fawcett, Jonathon
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at 18th World Congress of Soil Science, Philadelphia, Pennsylvania, USA : 9th-15th July 2006
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- Description: Soil is the component in the landscape along with land use management and vegetation that determines all the partitioning of water balance components that affect surface hydrology (runoff to waterways and wetlands) and recharge to groundwater. Most soil and land degradation processes are hydrologically driven or depend on hydrological conditions. Conceptual models and quantification of erosion processes (wind erosion is a result of lack of moisture), land salinisation, acidification, nutrient loss and impacts of nutrient movement, all require an understanding of the role of hydrology specific to the landscape under consideration. In Australia, salinity is a major problem for agriculture in irrigated and rainfed (‘dryland agriculture) land and has significant economic impacts in urban areas too. A general water balance approach has been used to conceptualise the processes and the problem. Large scale clearing of treed landscapes in favour of annual crops and pastures has been seen as the major change in the water balance of Australian landscapes since settlement. This change in vegetation and water use is frequently cited as the most significant factor in causing land salinisation, which is attributed to increase in groundwater recharge, mobilisation of salts, groundwater rise and discharge. We provide three case studies for landscapes that require quite different conceptual models and all of which are in some degree counter to the developed conventional wisdom regarding increased salinity. These case studies illustrate the importance of developing an appropriate conceptual model of hydrological processes in the ‘critical zone', in particular for implementation of policy and practice in land management. Case 1. South Eastern Dundas Tablelands, Victoria. In this landscape the apparent degradation of land by salinity is the result of changed hydrological conditions but has not resulted from increased groundwater discharge or increased salt accumulation. We have evidence that groundwater recharge and discharge have not increased since clearing of the landscape during European settlement. Laboratory hydrological studies in large diameter cores from soil and regolith, interpretation of redoximorphic features and functional horizons in the field and analysis of historical records of streamflow support this hypothesis. We also show that the degradation of salt affected areas is due to fluctuating waterlogging and drying of the soil causing cyclic redox conditions and changes in soil chemistry. Case 2. Dissected Coastal Plain, Victoria. In this landscape, slowly permeable marine clay overlain by coastal sand deposits provides a classic ‘layer cake' picture of differentially permeable material. The unconsolidated nature of the clays and the relatively deep dissection that exists presents a landslide prone landscape and one that also shows the effects of salting in low areas. In this region we show that upward pressure from a deep (200 m) confined freshwater aquifer maintains saturation in the marine clay and that waterlogging, landslides and salinity result from hydrological dynamics of the upper few metres of regolith and soil. Evidence has been collected from field survey, groundwater studies, geotechnical measurements and regolith mineralogy. Case 3. Granite Uplands, Victoria. In this landscape we have interpreted redoximorphic features of functional horizons and measurement of shallow groundwater salinities in a toposequence. Our conceptual model is of a regional saline groundwater system discharging in springs relatively high in the landscape. We show the role of shallow throughflow of water in the soil in spreading salt from these point sources, simultaneously diluting the effect of salinity in local drainage lines but increasing the area of salt affected land upslope from the drainage lines. In each case study area we have been compelled to develop an understanding that fits the landscape realities. We have used empirical observations and interpretation of soil morphology, regolith and groundwater characteristics, laboratory studies, soil chemistry and hydro-chemistry to support our work. We stress the importance of this approach integrating the sciences of hydrology, pedology, chemistry and geology in coming to appropriate conclusions about land degradation processes, especially if we are to advise on land management investment and policy to tackle degradation.
- Description: 2003002070
Hydropedology, Geomorphology, and Groundwater Processes in Land Degradation: Case Studies in South West Victoria, Australia
- Authors: MacEwan, Richard , Dahlhaus, Peter , Fawcett, Jonathon
- Date: 2012
- Type: Text , Book chapter
- Relation: Hydropedology p. 449-481
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Changes in dietary patterns and body composition within 12 months of liver transplantation
- Authors: McCoy, Simone , Campbell, Katrina , Lassemillante, Annie-Claude , Wallen, Matthew , Fawcett, Jonathon , Jarrett, Maree , Macdonald, Graeme , Hickman, Ingrid
- Date: 2016
- Type: Text , Journal article
- Relation: Hepatobiliary Surgery and Nutrition Vol.6 , no.5 (2017), p. 317-326
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- Description: Background: Cardiometabolic risk factors are increasing in liver transplant recipients (LTR). Influencing dietary factors have not been assessed. The aim of this observational study was to assess changes in weight, metabolic function, dietary intake and eating behaviours in the first year after orthotopic liver transplantation (OLT). Methods: Consecutive recruitment of 17 patients (14 males) awaiting OLT at a single tertiary hospital. Dietary intake, food behaviours and anthropometry were recorded at baseline, and 6 and 12 months posttransplant. Results: By 12 months, patients had gained on average 7.3% of body weight. The prevalence of overweight or obesity increased from baseline 53% to 77% (P=0.001). By 6 months, 65% (n=11/17) of patients had altered glucose metabolism. Dietary intake was consistent with a Western-style dietary pattern with high saturated fat. Over half of the patients (69%, n=11/16) reported low to no depressive feelings and rated their self-esteem as good (53%, n=9/16). The Power of Food Scale increased between pre and post-transplant, indicating a stronger appetitive drive. Conclusions: Weight gain occurs early post-transplant, with significant metabolic dysfunction present within 6 months, however is not associated with significant psychological distress. Early dietary intervention designed to limit weight gain and target cardiometabolic health is recommended for this unique patient population.