Lucas A.R.,University of Western Australia |
Salmon S.U.,University of Western Australia |
Rate A.W.,University of Western Australia |
Larsen S.,68 St. Georges Terrace |
Kilminster K.,68 St. Georges Terrace
Geochimica et Cosmochimica Acta | Year: 2015
This study reports the first surface water evaluation of the temporal and spatial variability of Au in an estuary, using recently developed modifications to the diffusive gradients in thin films (DGT) and grab sampling techniques. At the two study sites in the Swan River estuary that were more marine in character, the DGT-measured concentrations of Au (26.3 and 31.3. ng/L) were within the range of total concentrations measured on individual days (13.2-30.6. ng/L and 11.2-37.2. ng/L, respectively). In contrast, at an upstream site, Au concentrations measured by DGT were significantly lower than totals (3.9. ng/L for DGT, compared with 13.2-28.8. ng/L for grab sampling), likely due to either size exclusion of colloids (>70. nm) by DGT or formation of a dissolved, non-DGT-labile Au species (<0.45. μm). DGT-measured concentrations of other metals (Cu, Co, Cr, U, V, Mo and As) were also lower than total concentrations, although in contrast to DGT-measured Au, this phenomenon occurred at all sites. Furthermore, daily grab samples for Au, taken over the 10-day deployment (which included a rain event), showed that Au concentrations could spike substantially (from 15.1. ng/L to 37.2. ng/L) over intervals as short as one day. The combination of simultaneous deployment of different DGT devices and grab sampling represents a new development in efforts to understand the transport and fate of Au together with other elements in dynamic environments such as estuaries. © 2015 Elsevier Ltd.
Barron O.,CSIRO |
Silberstein R.,CSIRO |
Ali R.,CSIRO |
Donohue R.,68 St. Georges Terrace |
And 5 more authors.
Journal of Hydrology | Year: 2012
The effect of future climate scenarios on surface water and groundwater resources has been shown to have a consequent impact on water-dependent ecosystems. A regional-scale analysis of changes in water resources as a result of changing climate was undertaken in south-western Australia; a region with a large number of nationally and internationally recognised water-dependent ecosystems. The paper examines the potential environmental impacts of a substantial reduction in rainfall and an increase in temperature as projected by global climate models (GCMs) on river and groundwater-dependent terrestrial vegetation by 2030.Climate change effects on environmentally significant flow regimes were evaluated by applying the climate projections from 15 GCMs under three global warming 'scenarios to rainfall-runoff and groundwater models. It was estimated that under a dry future climate scenario, the frequency of river flow rates important for ecological communities is likely to be reduced by up to 2. months per year, which is likely to cause a significant level of stress to ecological communities. Additionally, the duration of no-flow periods may increase by more than 120. days in some streams. Under a dry future climate scenario, groundwater-dependent vegetation is projected to be at a high risk in over 19% of its current habitat area. Water-dependent ecosystems are also projected to be affected by an increase in groundwater abstraction. The results indicate that the projected impacts of future climate conditions are not likely to be uniform across the region but overall they could cause a continuing threat to water-dependent ecosystems. The implementation of water management plans should place particular emphasis on the ecological water requirements in 6 of the 13 river catchments in south-western Australia and in areas where groundwater abstraction is high. The climate projections and ecological impacts are a continuation of the trends that have taken place in the past three decades. © 2012.
Silberstein R.P.,CSIRO |
Aryal S.K.,CSIRO |
Durrant J.,68 St. Georges Terrace |
Pearcey M.,68 St. Georges Terrace |
And 7 more authors.
Journal of Hydrology | Year: 2012
This paper presents the results of computer simulations of runoff from 13 major fresh and brackish river basins in south-western Australia (SWA) under climate projections obtained from 15 GCMs with three future global warming scenarios equivalent to global temperature rises of 0.7 °C, 1.0 °C and 1.3 °C by 2030. The objective was to apply an efficient methodology, consistent across a large region, to examine the implications of the best available projections in climate trends for future surface water resources. An ensemble of rainfall-runoff models was calibrated on stream flow data from 1975 to 2007 from 106 gauged catchments distributed throughout the basins of the study area. The sensitivity of runoff to projected changes in mean annual rainfall is examined using the climate 'elasticity' concept. Averaged across the study area, all 15 GCMs project declines in rainfall under all global warming scenarios with a median decline of 8% resulting in a median decline in runoff of 25%. Such uniformity in projections from GCMs is unusual. Over SWA the average annual runoff under the 5th wettest and 5th driest of the 45 projections of the 2030 climate declines by 10 and 42%, respectively. Under the 5th driest projection the runoff decline ranges from 53% in the northern region to 40% in the southern region. Strong regional variations in climate sensitivity are found with the proportional decline in runoff greatest in the northern region and the greatest volumetric declines in the wetter basins in the south. Since the mid 1970s stream flows into the major water supply reservoirs in SWA have declined by more than 50% following a 16% rainfall reduction. This has already had major implications for water resources planning and for the preservation of aquatic and riparian ecosystems in the region. Our results indicate that this reduction in runoff is likely to continue if future climate projections eventuate. © 2012.