Olga Barron

An assessment of the climate change impacts on groundwater recharge at a continental scale using a probabilistic approach with an ensemble of GCMs

This study used 16 Global Climate Models and three global warming scenarios to make projections of recharge under a 2050 climate for the entire Australian continent at a 0.05° grid resolution. The results from these 48 future climate variants have been fitted to a probability distribution to enable the results to be summarised and uncertainty quantified. The median results project a reduction in recharge across the west, centre and south of Australia and an increase in recharge across the north and a small area in the east of the continent. The range of results is quite large and for large parts of the continent encompasses both increases and decreases in recharge. This makes it difficult to utilise for water resources management so the results have been analysed with a risk analysis framework; this enables the future projections for groundwater recharge to be communicated to water managers in terms of likelihood and consequence of a reduction in recharge. This highlights an important message for water resource managers that in most areas of Australia they will be making decisions on water allocations under considerable uncertainty as to the direction and magnitude of recharge change under a future climate and that this uncertainty may be irreducible.

Identification of phosphorus export from low-runoff yielding areas using combined application of high frequency water quality data and MODHMS modelling

In basins combining flat-sandy valleys and hilly-bedrock sub-catchments, the assessment of nutrient (phosphorus) exports from low-runoff yielding environments is difficult. To overcome this issue hydrological modelling and high frequency phosphorus measurements were simultaneously employed. A coupled surface water-groundwater interaction model (MODHMS) was used to determine runoff from the low-runoff yielding part of the catchment. The modelling results indicated that the lower catchment contributed less than 10% of annual catchment discharge over a number of weeks during mid-winter. High frequency phosphorus (P) measurements showed a threefold increase in P concentration during this period in 2008, which lasted for 3 weeks. Concentration-discharge analysis suggested that the increase in P concentration was associated with runoff generation processes in the low-runoff yielding sub-catchment. It was estimated that this area contributed 32% of the annual P load though only 2% of total annual discharge in 2008. Both runoff and P contributions occurred during the period when the water table rose to the surface causing inundation. It was shown that the P concentrations in discharge from the low-runoff yielding sub-catchment were similar to those observed in the shallow groundwater layers.

Application of thermal remote sensing to delineate groundwater discharge zones.

The paper explores whether thermal anomalies at the surface identified by remote sensing allow for the delineation of groundwater discharge zones. The methodology is based on the principle that in shallow groundwater systems, upward fluxes of deep groundwater discharge reduces seasonal temperature variation in layers close to and at the surface. Thermal anomalies were identified by Landsat data and compared between two winter images separated by 11 years during which a large drainage scheme was implemented. Though there were a number of limiting factors defined, the approach proved useful for identifying groundwater discharge zones at the study site.

Delineation of riparian vegetation from Landsat multi‐temporal imagery using PCA

A deficiency in crucial digital data, such as vegetation cover, in remote regions is a challenging issue for water management and planning, especially for areas undergoing rapid development, such as mining in the Pilbara, Western Australia. This is particularly relevant to riparian vegetation, which provides important ecological services and, as such, requires regional protection. The objective of this research was to develop an approach to riparian vegetation mapping at a regional scale using remotely sensed data. The proposed method was based on Principal Component Analysis (PCA) applied to multi-temporal Normalised Difference Vegetation Index (NDVI) datasets derived from Landsat TM 5 imagery. To delimit the spatial extent of riparian vegetation, a thresholding method was required and various thresholding algorithms were tested. The accuracy of results was estimated for various NDVI multi-temporal datasets using available ground-truth data. The combination of a 14-dry-date dataset and Kittlers thresholding method provided the most accurate delineation of riparian vegetation. This article is protected by copyright. All rights reserved.

Large-scale regional delineation of riparian vegetation in the arid and semi-arid Pilbara region, WA

Multi-scene Landsat 5 TM imagery, Principal Component Analysis (PCA), and the Normalised Difference Vegetation Index (NDVI) were used to produce the first region-scale map of riparian vegetation for the Pilbara (230,000 km2), Western Australia. Riparian vegetation is an environmentally important habitat in the arid and desert climate of the Pilbara. These habitats are supported by infrequent flow events and in some locations by groundwater discharge. Our analysis suggests that riparian vegetation covers less than 4% of the Pilbara region, while almost 10.5% of this area is comprised of Groundwater Dependent Vegetation (GDV). GDV is often associated with open water (river pools), providing refugia for a variety of species. GDV has an extremely high ecological value and are often important Indigenous sites. This paper demonstrates how Landsat data calibrated to Top of Atmosphere (TOA) reflectance can be used to delineate riparian vegetation across 16 Landsat Scenes and two UTM (Universal Transverse Mercator) spatial zones. The proposed method is able to delineate riparian vegetation and GDV, without the need for Bidirectional Reflectance Distribution Function (BRDF) correction. Results were validated using ground-truth data from local and regional scale vegetation surveys.

Multivariate detection and attribution of land-cover changes in the Central Pilbara, Western Australia

The Multivariate Alteration Detection (MAD) method was applied to locate areas where land-cover changes occurred between 2003 and 2009 in the Central Pilbara, Western Australia. It was demonstrated that each of the six MAD variates contained information of land-cover changes at various spatial scales. This allowed attribution of the identified changes to particular stressors such as climate variability, fire events, and mining activity in the area. The results were analysed and interpreted using time series of multispectral normalized difference vegetation index, normalized difference wetness index, and normalized burn ratio grids derived from Landsat data observed over the study period. In addition, various ground truth data such as fire maps, historical climate data, and the available information about mine operations and water management, which could lead to alteration of natural water regime, were utilized.

3D exploratory analysis of descriptive lithology records using regular expressions

This paper presents an interactive approach for analyzing a database of descriptive lithology records to locate a specific lithology feature in three-dimensional space. The method uses a regular expression to search individual lithology records, assigning a match score to indicate the relative strength of a search result. Spatial analysis of the resulting match scores generates a three-dimensional representation of the search results, which indicates the likely locations of the lithology feature. The method enables direct analysis of lithology descriptions, which are often characterized by inconsistencies in terminology, accuracy, level of detail, and spatial distribution. Using regular expressions, the approach circumvents the need for manual interpretation and classification of lithology records. The method was applied to a case study area in Western Australia to delineate the extent of three lithology features (clay, calcareous sediments, and iron-rich sediments). The approach is generally applicable for layered lithology features that are regularly documented in a lithology database.

A comparative evaluation of arid inflow-dependent vegetation maps derived from LANDSAT top-of-atmosphere and surface reflectances

ABSTRACT In remote sensing, it is commonly accepted that land remote-sensing satellite (LANDSAT) top-of-atmosphere (TOA) reflectance is less accurate than atmospheric correction (AC) reflectance, as the former is not calibrated for possible modifications in the electromagnetic radiation signals due to atmospheric scattering and absorption. This article investigates whether LANDSAT data calibrated for TOA reflectance are an appropriate information source for delineating inflow-dependent vegetation (IDV) in regions with an arid and desert climate, such as the Pilbara region in Western Australia. Knowledge of where IDVs are in the landscape underpins planning their protection and define the baseline for their monitoring when water resource management options are considered. The appropriateness of TOA calibration for the delineation of IDV in the Pilbara was assessed through its comparison with IDV maps derived from AC reflectance. Both radiometric calibration methods (TOA and AC) were applied to a multi-date LANDSAT 5 TM (Thematic Mapper) dataset of 10 images acquired in 2009 and 2010. Two methods based on the application of remote-sensing techniques to identify the extent of temporally invariant vegetation were applied for IDV delineation in the study area. The first method, groundwater-dependent ecosystems mapping (GEM), employs a two-date normalized difference vegetation index (NDVI) dataset for identifying ‘no-change’ clusters of land cover and detecting those related to IDV. The second method applies principal component analysis (PCA) to a multi-date NDVI dataset. The first principal component (PC1) typically contains features that remain unchanged over time. This includes vegetation with continuous or frequent access to surface and/or groundwater, such as IDV. To delineate the extent of IDV, a thresholding technique was further employed. Spatial similarity between IDV maps produced from TOA and AC reflectance was quantitatively evaluated by the Kappa coefficient. The results showed that TOA and AC IDV maps are in ‘almost perfect’ agreement with the Kappa values above 0.83. This suggests that TOA reflectance is equally appropriate to AC reflectance for mapping in arid and desert climate such as in Pilbara. When the GEM- and PCA-based methods are applied in other study areas with arid or desert climate, the accuracy of the delineated IDV extent may vary. Therefore, the results need to be validated using ground-truth information about known IDV occurrences in the area of interest.

Groundwater Resource Assessment and Conceptualization in the Pilbara Region, Western Australia

The Pilbara region is one of the most important mining hubs in Australia. It is also a region characterised by an extreme climate, featuring environmental assets of national significance, and considered a valued land by indigenous people. Given the arid conditions, surface water is scarce, shows large variability, and is an unreliable source of water for drinking and industrial/mining purposes. In such conditions, groundwater has become a strategic resource in the Pilbara region. To date, however, an integrated regional characterization and conceptualization of the occurrence of groundwater resources in this region were missing. This article addresses this gap by integrating disperse knowledge, collating available data on aquifer properties, by reviewing groundwater systems (aquifer types) present in the region and identifying their potential, and proposing conceptualizations for the occurrence and functioning of the groundwater systems identified. Results show that aquifers across the Pilbara Region vary substantially and can be classified in seven main types: coastal alluvial systems, concealed channel iron deposits, inland valley-fill aquifers, karstified dolomites, sandstone aquifers (West Canning Basin), Permian/Cenozoic Paleochannels, and Fractured Rock aquifers. Coastal alluvial systems show the greatest regional potential as water sources and are currently intensively utilised. Conceptually, the main recharge processes are infiltration of precipitation associated with cyclonic events and the interaction with streamflows during summer season, whereas the main discharge mechanisms correspond to evapotranspiration from riverine and coastal vegetation, discharge into the Indian Ocean, and dewatering of iron-ore bodies to facilitate mining activities. Important gaps in the knowledge relate to aquifer connectivity and accurate quantification of recharge/discharge mechanisms.