University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains... more University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- The effects of flow regulation and to a lesser extent flow restoration on stream ecosystems are increasingly well documented and studied internationally. Australian stream ecosystems have changed in response to flow alteration, but little is known how they might change should flow volumes and variability increase through the introduction of environmental flows. The Severn River is an upland river in northern NSW, Australia. It is a tributary of the Border Rivers sub-catchment, a part of the Murray–Darling River System. Pindari Dam on the Severn River, which can store 312 GL, regulates its flow. Typically, high flows to meet irrigation demands (up to 1,000 ML d⁻¹) occur in warmer months (October-March). Unlike many other regulated rivers that experience higher flows than pre-regulated conditions in summer, the seasonality of high flows in the Severn River has not been reversed. However, natural flow variation is lost as releases of ~10 ML d⁻¹ are discharged at other times. A Water Sharing Plan (WSP) governs management of flows in the Severn River including an environmental flow release from Pindari Dam. Seasonal water chemistry, benthic algal and macroinvertebrate assemblage data were collected at sites on the regulated Severn and unregulated Mole and Dumaresq Rivers. Sites differed in the level of hydrological variation. Flows in the Severn River never ceased and were relatively stable, compared to unregulated sites on the Mole and Dumaresq Rivers that experienced high flows after rainfall and no flow periods when base flows ceased. Severn River sites had a higher abundance of benthic algae (including filamentous algae) but lower algal diversity than that at sites of the Mole and Dumaresq Rivers. Macroinvertebrate densities in all rivers were comparable; however, regulated sites were typically characterised by a higher density of filter feeding macroinvertebrates. Two environmental flow scenarios designed to reduce the density of benthic algae were trialled in the Severn River at Glenora Bridge and Ashford Bridge. Flows that peaked at ~1,000 ML d⁻¹ (velocity of ~0.9 m s⁻¹) increased the density of benthic algae particularly filamentous algae such as Stigeoclonium and Leptolyngbya. A third flow event from an unregulated tributary with its confluence between sites, increased flows to 2,180 ML d⁻¹ (velocity of ~1.2 m s⁻¹), which reduced chlorophyll a and filamentous algal abundance. The similarity in flow velocities suggests that suspended sediments in the unregulated tributary flow may be important in reducing of algal biomass. Benthic algal biomass accrual (measured as chlorophyll a concentration) and community changes were determined after artificial scouring of cobbles. Algal biomass and diversity on scoured cobbles took two weeks to return to levels similar to that on the reference cobbles in summer and took five weeks in winter. Chlorophyll a concentrations on cobbles in summer were initially 0.24 ± 0.06 mg m⁻², but by day 16 had increased to 9.74 ± 1.97 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Chlorophyll a concentrations in winter were initially 0.47 ± 0.13 mg m⁻², but by day 37 increased to 44.7 ± 10.9 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Peak chlorophyll a concentration accrual during summer and winter was 1.64 and 2.63 mg m d⁻¹, respectively. Diatoms such as Cocconeis, Synedra, and Fragilaria dominated the early succession assemblages, while an abundance of the filamentous green alga Stigeoclonium indicated a late succession assemblage. The Severn River does not experience natural flow variations and periods of drying due to dam operation, although naturally they would have occurred. Summer and winter experiments to determine the response of algal assemblages to drying for 1, 2, 4 or 9 d and re-immersion periods of 13 or 28 d were performed to determine if drying could be used to reduce biomass and re-set algae to early stage assemblages. In winter, drying reduced the abundance of green algae, including Stigeoclonium and other filamentous algal taxa. Chlorophyll a concentrations declined from 22.92 ± 4.71 mg m⁻² to 4.85 ± 0.42 mg m⁻². In summer, drying promoted the growth of Cocconeis and chlorophyll a concentrations were stable at 2.33 ± 0.36 mg m⁻². A grazer-exclusion experiment was conducted to determine macroinvertebrate grazing preferences for early and late succession algal assemblages. Grazers did not prefer the early succession algal assemblages as expected; instead, more grazers were found on late succession cobbles. Treatments with grazing increased chlorophyll a concentrations (from 9.69 ± 0.69 mg m⁻² to 13.15 ±…
A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental ... more A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental flows (EFs) are designed to increase the magnitude of flow and improve ecological outcomes such as reducing filamentous algal biomass and re-setting algal succession. The effectiveness of EF releases to alter benthic algal assemblages is poorly understood. We examined benthic algal biomass and assemblage structure at two cobble-dominated riffle sites downstream of Pindari Dam, before and after two EFs. Both EFs had discharges of ~11.6 m3 s–1 (velocity of ~0.9 m s–1). Neither EF reduced benthic algal biomass, and sometimes led to increases, with density of some filamentous algae increasing (Stigeoclonium and Leptolyngbya). An unregulated flow from a tributary between the two sites increased discharge to 25.2 m3 s–1 (velocity of ~1.2 m s–1), decreasing biomass and density of filamentous algae. The similarity in flow velocities between scouring and non-scouring events suggests that threshol...
... SM Mitrovic (&) Á BC Chessman Á EL Avery Á N. Ryan NSW De... more ... SM Mitrovic (&) Á BC Chessman Á EL Avery Á N. Ryan NSW Department of Water and Energy, PO Box 3720, Parramatta, NSW 2124 ... were obtained from two sites with frequent diatom blooms: the Hunter River at Bowmans Crossing and the Hunter River at Moses Crossing (Fig. ...
Decaying fish play an important role in delivering nutrients into rivers and lakes but can create... more Decaying fish play an important role in delivering nutrients into rivers and lakes but can create water quality issues. The release of cyprinid herpesvirus-3 (CyHV-3) in Australia with an associated mass common carp mortality may have serious effects on water quality in lakes. To evaluate the effect of a virus-induced fish kill, different biomasses of dead common carp (250–6000kgha–1) were placed into 2000-L mesocosms within Prospect Reservoir, Australia, for up to 40 days. Decaying carp created anoxic conditions within all treatments except the 250kgha–1 treatment, in which oxygen saturation dropped to 30%. A higher biomass of carp led to longer periods of anoxia. Total nitrogen (TN) increased from a baseline of 0.25 to 1.5–30mgL–1 in the different treatments, whereas total phosphorus (TP) increased from 0.01 to 0.05–5.0mgL–1. Chlorophyll-a levels increased from <5µgL–1 to levels between 100 and 1000µgL–1 in the different treatments. Mean nutrient levels (TN and TP), chlorophyll...
Abstract Flow releases from dams can be used to scour benthic algae, simulating the effects of na... more Abstract Flow releases from dams can be used to scour benthic algae, simulating the effects of natural spates and maintaining benthic algae in an early successional stage for increased grazer palatability. The timing of releases needs to consider the natural periodicity of flow ...
University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains... more University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- The effects of flow regulation and to a lesser extent flow restoration on stream ecosystems are increasingly well documented and studied internationally. Australian stream ecosystems have changed in response to flow alteration, but little is known how they might change should flow volumes and variability increase through the introduction of environmental flows. The Severn River is an upland river in northern NSW, Australia. It is a tributary of the Border Rivers sub-catchment, a part of the Murray–Darling River System. Pindari Dam on the Severn River, which can store 312 GL, regulates its flow. Typically, high flows to meet irrigation demands (up to 1,000 ML d⁻¹) occur in warmer months (October-March). Unlike many other regulated rivers that experience higher flows than pre-regulated conditions in summer, the seasonality of high flows in the Severn River has not been reversed. However, natural flow variation is lost as releases of ~10 ML d⁻¹ are discharged at other times. A Water Sharing Plan (WSP) governs management of flows in the Severn River including an environmental flow release from Pindari Dam. Seasonal water chemistry, benthic algal and macroinvertebrate assemblage data were collected at sites on the regulated Severn and unregulated Mole and Dumaresq Rivers. Sites differed in the level of hydrological variation. Flows in the Severn River never ceased and were relatively stable, compared to unregulated sites on the Mole and Dumaresq Rivers that experienced high flows after rainfall and no flow periods when base flows ceased. Severn River sites had a higher abundance of benthic algae (including filamentous algae) but lower algal diversity than that at sites of the Mole and Dumaresq Rivers. Macroinvertebrate densities in all rivers were comparable; however, regulated sites were typically characterised by a higher density of filter feeding macroinvertebrates. Two environmental flow scenarios designed to reduce the density of benthic algae were trialled in the Severn River at Glenora Bridge and Ashford Bridge. Flows that peaked at ~1,000 ML d⁻¹ (velocity of ~0.9 m s⁻¹) increased the density of benthic algae particularly filamentous algae such as Stigeoclonium and Leptolyngbya. A third flow event from an unregulated tributary with its confluence between sites, increased flows to 2,180 ML d⁻¹ (velocity of ~1.2 m s⁻¹), which reduced chlorophyll a and filamentous algal abundance. The similarity in flow velocities suggests that suspended sediments in the unregulated tributary flow may be important in reducing of algal biomass. Benthic algal biomass accrual (measured as chlorophyll a concentration) and community changes were determined after artificial scouring of cobbles. Algal biomass and diversity on scoured cobbles took two weeks to return to levels similar to that on the reference cobbles in summer and took five weeks in winter. Chlorophyll a concentrations on cobbles in summer were initially 0.24 ± 0.06 mg m⁻², but by day 16 had increased to 9.74 ± 1.97 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Chlorophyll a concentrations in winter were initially 0.47 ± 0.13 mg m⁻², but by day 37 increased to 44.7 ± 10.9 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Peak chlorophyll a concentration accrual during summer and winter was 1.64 and 2.63 mg m d⁻¹, respectively. Diatoms such as Cocconeis, Synedra, and Fragilaria dominated the early succession assemblages, while an abundance of the filamentous green alga Stigeoclonium indicated a late succession assemblage. The Severn River does not experience natural flow variations and periods of drying due to dam operation, although naturally they would have occurred. Summer and winter experiments to determine the response of algal assemblages to drying for 1, 2, 4 or 9 d and re-immersion periods of 13 or 28 d were performed to determine if drying could be used to reduce biomass and re-set algae to early stage assemblages. In winter, drying reduced the abundance of green algae, including Stigeoclonium and other filamentous algal taxa. Chlorophyll a concentrations declined from 22.92 ± 4.71 mg m⁻² to 4.85 ± 0.42 mg m⁻². In summer, drying promoted the growth of Cocconeis and chlorophyll a concentrations were stable at 2.33 ± 0.36 mg m⁻². A grazer-exclusion experiment was conducted to determine macroinvertebrate grazing preferences for early and late succession algal assemblages. Grazers did not prefer the early succession algal assemblages as expected; instead, more grazers were found on late succession cobbles. Treatments with grazing increased chlorophyll a concentrations (from 9.69 ± 0.69 mg m⁻² to 13.15 ±…
A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental ... more A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental flows (EFs) are designed to increase the magnitude of flow and improve ecological outcomes such as reducing filamentous algal biomass and re-setting algal succession. The effectiveness of EF releases to alter benthic algal assemblages is poorly understood. We examined benthic algal biomass and assemblage structure at two cobble-dominated riffle sites downstream of Pindari Dam, before and after two EFs. Both EFs had discharges of ~11.6 m3 s–1 (velocity of ~0.9 m s–1). Neither EF reduced benthic algal biomass, and sometimes led to increases, with density of some filamentous algae increasing (Stigeoclonium and Leptolyngbya). An unregulated flow from a tributary between the two sites increased discharge to 25.2 m3 s–1 (velocity of ~1.2 m s–1), decreasing biomass and density of filamentous algae. The similarity in flow velocities between scouring and non-scouring events suggests that threshol...
... SM Mitrovic (&amp;amp;amp;amp;amp;amp;amp;amp;) Á BC Chessman Á EL Avery Á N. Ryan NSW De... more ... SM Mitrovic (&amp;amp;amp;amp;amp;amp;amp;amp;) Á BC Chessman Á EL Avery Á N. Ryan NSW Department of Water and Energy, PO Box 3720, Parramatta, NSW 2124 ... were obtained from two sites with frequent diatom blooms: the Hunter River at Bowmans Crossing and the Hunter River at Moses Crossing (Fig. ...
Decaying fish play an important role in delivering nutrients into rivers and lakes but can create... more Decaying fish play an important role in delivering nutrients into rivers and lakes but can create water quality issues. The release of cyprinid herpesvirus-3 (CyHV-3) in Australia with an associated mass common carp mortality may have serious effects on water quality in lakes. To evaluate the effect of a virus-induced fish kill, different biomasses of dead common carp (250–6000kgha–1) were placed into 2000-L mesocosms within Prospect Reservoir, Australia, for up to 40 days. Decaying carp created anoxic conditions within all treatments except the 250kgha–1 treatment, in which oxygen saturation dropped to 30%. A higher biomass of carp led to longer periods of anoxia. Total nitrogen (TN) increased from a baseline of 0.25 to 1.5–30mgL–1 in the different treatments, whereas total phosphorus (TP) increased from 0.01 to 0.05–5.0mgL–1. Chlorophyll-a levels increased from <5µgL–1 to levels between 100 and 1000µgL–1 in the different treatments. Mean nutrient levels (TN and TP), chlorophyll...
Abstract Flow releases from dams can be used to scour benthic algae, simulating the effects of na... more Abstract Flow releases from dams can be used to scour benthic algae, simulating the effects of natural spates and maintaining benthic algae in an early successional stage for increased grazer palatability. The timing of releases needs to consider the natural periodicity of flow ...
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