New South Wales Office of Water

City of Parramatta, Australia

New South Wales Office of Water

City of Parramatta, Australia
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Brooks A.J.,New South Wales Office of Water | Chessman B.C.,Climate Change and Water | Haeusler T.,New South Wales Office of Water
Journal of the North American Benthological Society | Year: 2011

The biological effect of water abstraction from unregulated streams in New South Wales, Australia, was assessed with data on macroinvertebrate assemblages in riffles (445 samples) and pool edges (718 samples) obtained from a national assessment of river condition in 1995 to 2000. We used limiting environmental difference (LED) modeling to predict the macroinvertebrate assemblage expected for each sample in the absence of water abstraction and estimated effect by comparing predicted and observed assemblages for sites with upstream abstraction. We found a high likelihood of effect on macroinvertebrates in 30% of riffles with upstream abstraction and 22% of edges. Complex combinations of biological traits appeared to determine the sensitivities and tolerances of individual taxa to water abstraction. For example, rheophilous families generally were rarer than predicted in apparently affected riffles, where thermophilic families seemed tolerant of the effects of water abstraction, and free-swimming families were less common than predicted in apparently affected edges, where families with tegument respiration appeared unaffected by water withdrawals. The trait response was clearer for the riffle fauna than for the edge fauna, perhaps because the physical and chemical effects of abstraction are more consistent for riffles than for edges. Our approach can support management planning by identifying taxa that are most at risk from water abstraction and sites where apparent effects are most evident. © 2011 The North American Benthological Society.

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 | Year: 2012

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.

Rolls R.J.,University of New England of Australia | Rolls R.J.,Griffith University | Boulton A.J.,University of New England of Australia | Growns I.O.,New South Wales Office of Water | And 3 more authors.
Hydrobiologia | Year: 2012

Environmental flow rules are developed to provide a flow regime necessary to maintain healthy river and floodplain ecosystems in rivers regulated for human uses. However, few studies have experimentally assessed potential ecological mechanisms causing declines in the health and productivity of freshwater fish assemblages in regulated rivers to inform the development of appropriate environmental flows. We tested whether an experimental flow release in a regulated tributary of the Hunter River, Australia, altered the diet of two widely distributed fish species (Australian smelt Retropinna semoni and Cox's gudgeon Gobiomorphus coxii) compared with data from unregulated reference and regulated control tributaries. Neither species had significant differences in the number of prey taxa ingested, gut fullness or composition of gut contents due to the environmental flow release (EFR). The diet of R. semoni did not differ significantly between regulated and unregulated tributaries in either catchment. However, the diet of G. coxii differed in only one of the two pairs of rivers consistently across all sample times. Assuming the EFR was sufficient to alter the composition of prey available for consumption by the fish species studied, our findings imply that functional indicators, such as the diet of generalist higher-order consumers, may be more suitable indicators of long-term flow regime change rather than short-term flow events. © 2012 Springer Science+Business Media B.V.

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 | Year: 2014

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.

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 | Year: 2010

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.

Westhorpe D.P.,New South Wales Office of Water | Westhorpe D.P.,University of Technology, Sydney | Mitrovic S.M.,New South Wales Office of Water | Mitrovic S.M.,University of Technology, Sydney | And 2 more authors.
Hydrobiologia | Year: 2010

Flow regulation in lowland rivers has reduced the amount of allochthonous dissolved organic carbon (DOC) entering main channels through less frequent wetting of benches, flood runners and floodplains. The hypothesis tested was that lowland riverine bacterioplankton are DOC limited when flow events are absent and simulating an increase in assimilable DOC similar to that expected during an environmental flow will lead to heterotrophic dominance. Experiments took place in the Namoi River, a highly regulated lowland river in Australia. Specifically, in situ microcosms were used to examine the responses of bacterioplankton and phytoplankton to various additions of DOC as glucose or leaf leachate, with and without additions of inorganic nutrients. The results indicated that ambient DOC availability limited the bacterioplankton for the three seasons over which we conducted the experiments. When DOC was added alone, dissolved oxygen concentrations decreased primarily because of increased bacterial respiration and bacterioplankton growth generally increased relative to controls. Additions of DOC alone led to a pattern of decreased chlorophyll a concentration relative to controls, except for willow leachate. Additions of inorganic nutrients alone increased chlorophyll a concentrations above controls, indicating limitation of phytoplankton. These findings support our hypothesis. Based on the present results, environmental flows should increase the duration of allochthonously driven heterotrophic dominance, thus shifting regulated lowland rivers to more natural (pre-regulation) conditions for greater periods. © 2010 Springer Science+Business Media B.V.

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 | Year: 2012

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.

McCallum J.L.,Water for A Healthy Country National Research Flagship | Cook P.G.,Water for A Healthy Country National Research Flagship | Cook P.G.,Flinders University | Brunner P.,Flinders University | Berhane D.,New South Wales Office of Water
Water Resources Research | Year: 2010

Chemical base flow separation is a widely applied technique in which contributions of groundwater and surface runoff to streamflow are estimated based on the chemical composition of stream water and the two end-members. This method relies on the assumption that the groundwater end-member can be accurately defined and remains constant. We simulate solute transport within the aquifer during and after single and multiple river flow events, to show that (1) water adjacent to the river will have a concentration intermediate between that of the river and that of regional groundwater and (2) the concentration of groundwater discharge will approach that of regional groundwater after a flow event but may take many months or years before it reaches it. In applying chemical base flow separation, if the concentration in the river prior to a flow event is used to represent the pre-event or groundwater end-member, then the groundwater contribution to streamflow will be overestimated. Alternatively, if the concentration of regional groundwater a sufficient distance from the river is used, then the pre-event contribution to streamflow will be underestimated. Changes in concentration of groundwater discharge following changes in river stage predicted by a simple model of stream-aquifer flows show remarkable similarity to changes in river chemistry measured over a 9 month period in the Cockburn River, southeast Australia. If the regional groundwater value was used as the groundwater end-member, chemical base flow separation techniques would attribute 8% of streamflow to groundwater, as opposed to 25% if the maximum stream flow value was used. © 2010 by the American Geophysical Union.

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.

Brooks A.J.,New South Wales Office of Water | Russell M.,New South Wales Office of Water | Bevitt R.,New South Wales Office of Water | Dasey M.,New South Wales Office of Water
Marine and Freshwater Research | Year: 2011

The impacts of river regulation on aquatic biota have been extensively studied, but long-term assessments of the restoration of biota by environmental flows and the principal mechanisms of recovery have rarely occurred. We assessed whether the provision of an environmental flow regime (EFR) via the decommissioning of an aqueduct on a tributary stream altered downstream macroinvertebrate assemblages in the highly regulated Snowy River, Australia. Macroinvertebrate assemblages of the Snowy River, reference and control sites remained distinct despite the provision of environmental flows. Invertebrate assemblages detrimentally affected by regulation probably remained impaired due to either constraints on colonisation from the tributary stream (dispersal constraints) or unsuitable local environmental conditions in the Snowy River caused by flow regulation (e.g. high levels of fine sediments, elevated temperature regime) suppressing new colonists or recovery of extant populations. Our study showed that restoration may be ineffective if EFRs are too small to ameliorate local environmental factors constraining the recovery of affected biota. Other barriers to recovery, such as dispersal constraints, also need to be overcome. Successful restoration of regulated rivers using environmental flows requires an understanding of the mechanisms and pathways of recovery, together with identification and amelioration of any potential barriers to recovery. © 2011 CSIRO.

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