Time filter

Source Type

City of Parramatta, Australia

Mitrovic S.M.,University of Technology, Sydney | Hitchcock J.N.,University of Technology, Sydney | Davie A.W.,University of Technology, Sydney | Ryan D.A.,New South Wales Office of Water
Journal of Plankton Research

The growth of Cyclotella meneghiniana was examined at temperatures between 13 and 28°C at 3°C intervals. Growth increased linearly with temperature to a growth maximum at 25°C, with growth decreasing at 28°C. © The Author 2010. Source

Irrigation of pasture forms the greatest single use of irrigation water in Australia yet there has been little monitoring of its spatial extent and water demands across southeast Australian coastal catchments where irrigated dairy farming forms an important rural livelihood. This paper provides an analysis of spatio-temporal patterns in the extent of irrigated pasture in the Bega-Bemboka catchment on the south coast of New South Wales from Landsat imagery, and establishes quantile regression relationships between metered monthly irrigation abstraction volumes, evaporation and rainfall. Over the metering period (2000-2007), annual water usage averages 4.8 ML ha -1 year -1, with January being the month of highest demand with an annualised usage of 10.4 ML ha -1 year -1. Analysis of Landsat imagery indicates that the spatial extent of irrigated pasture across the catchment has increased from 1266 ha in 1983 to 1842 ha by 2002, together with amalgamation of smaller holdings along less reliable streams into larger parcels along the trunk stream. Quantile regressions to estimate monthly mean and maximum abstraction volumes from monthly evaporation and rainfall data indicate that abstraction volumes are more closely correlated with evaporation. When combined with Landsat analyses of the spatial extent of irrigated areas, such relationships enable estimation of catchment-scale hydrological effects of irrigation abstractions that in turn can help guide regional-scale assessments of the ecological effects and sustainability of spatially and temporally changing irrigation abstraction volumes. © 2011 Her Majesty the Queen in Right of Australia. Source

Westhorpe D.P.,New South Wales Office of Water | Westhorpe D.P.,University of Technology, Sydney | Mitrovic S.M.,University of New South Wales | Mitrovic S.M.,University of Technology, Sydney
Marine and Freshwater Research

The relationships between discharge and dissolved organic carbon (DOC) have been extensively studied in rainfall runoff-driven stream systems. Less is known about discharge and DOC relationships in river systems dependent on floodplain inundation. We examined DOC dynamics and mobilisation over low discharge periods and several larger discharge events in the highly regulated lowland Namoi River, Australia. Stable isotope signatures (δ 13C) of various water-column fractions (e.g. 200μm, fine particulate organic matter) were used to determine the sources of DOC. DOC concentrations over low discharge periods were fairly similar among sites and ranged between 5 and 10mgL-1. Concentrations during a high-discharge event increased substantially with a mean of 20.4mgL-1 and a maximum of 44mgL-1. Significant positive linear relationships were found between DOC concentrations and discharge (P<0.001, r2≤0.45). The 13C composition of DOC sampled across the three sites (e.g.-26.2‰) suggests a mixture of terrestrial and aquatic sources, with little downstream variation; however, we would envisage that during periods of high discharge allochthonous sources would dominate. Environmental flows (that are ecologically beneficial, potentially reversing changes brought about by flow regulation) have been allocated to the river, with the intention to increase the amount of DOC delivered to the river. The relationship between DOC and discharge was used to estimate DOC loads to the river under different modelled flow-management scenarios, including without environmental flow, with environmental flow, and simulated natural (low development) flow. On the basis of the modelling results, environmental flows should increase the amount of allochthonous DOC transported within the river in years with moderate and large flow events. Years with low flows did not deliver large loads of allochthonous DOC. The present results showed the potential variability in DOC delivery in relation to floodplain inundation in a lowland river that may not otherwise be detected in rainfall/runoff-driven headwater streams. © 2012 CSIRO. Source

Growns I.,New South Wales Office of Water | Chessman B.,New South Wales Office of Environment and Heritage | Mitrovic S.,New South Wales Office of Environment and Heritage | Mitrovic S.,University of Technology, Sydney | Westhorpe D.,New South Wales Office of Water
Journal of Freshwater Ecology

We examined the effects of two dams on longitudinal variation of riverine food webs using stable isotope and gut contents analyses along four rivers in the Hunter Valley in eastern Australia. Longitudinal 15N enrichment was observed in most invertebrate taxa and food sources but significant longitudinal variation was rare for 13C, and composition of gut contents of invertebrate taxa did not vary significantly with longitudinal position. Most invertebrates and food sources were more 15N-enriched at sites immediately downstream of the dams than expected from their upstream longitudinal position, a result not mirrored by gut contents and 13C. Enrichment of 15N downstream may be attributed to altered water quality as a result of impoundment but further research is necessary to elucidate whether physico-chemical riverine processes or trophic mechanisms are responsible. Our observations regarding the influence of dams on isotope ratios are contrary to the few existing studies, suggesting the small volumes relative to annual inflows of dams in the present study limit downstream impacts by maintaining aspects of flow variability. © 2013 © 2013 Taylor & Francis. Source

McCallum J.L.,CSIRO | McCallum J.L.,Flinders University | Cook P.G.,CSIRO | Cook P.G.,Flinders University | And 2 more authors.
Journal of Hydrology

While estimates of net groundwater inflow to streams (inflow minus outflow) can be made using differential flow gauging, the inclusion of water chemistry (tracer) measurements allows both inflow and outflow to be separately quantified. In this paper we assess how the estimates of net and gross groundwater inflows are affected by the choice of tracer at three contrasting field sites. Groundwater flows are first estimated with differential flow gauging and then with the sequential addition of natural tracer data - electrical conductivity, chloride concentration and radon activity measurements. The final analysis is where an injected tracer experiment is also conducted to constrain the gas transfer velocity for radon. Groundwater inflow rates were estimated by calibrating a numerical model which simulated flows and concentrations of tracers in the river. Although both the total groundwater inflow along the study reach and the spatial distribution of inflow depended on the data used for the model calibration, the difference between the estimates was less than the prediction error. The analysis also showed that prediction error for groundwater inflow decreases as additional tracers are included in the analysis. The magnitude of the error reduction is related to the properties of the specific catchment. Generally, for a tracer to reduce uncertainty substantially the concentration of the tracer in groundwater must be well defined, and the contrast between the concentration of the tracer in groundwater and the river must be high. © 2011 Elsevier B.V. Source

Discover hidden collaborations